Merge branch 'preview' into listing-tweaks

23 files changed, 2838 insertions, 107 deletions

diff --git a/test/lib/content-function.js b/test/lib/content-function.js
index bb12be82..5cb499b1 100644
--- a/test/lib/content-function.js
+++ b/test/lib/content-function.js
@@ -1,5 +1,6 @@
 import * as path from 'node:path';
 import {fileURLToPath} from 'node:url';
+import {inspect} from 'node:util';
 
 import chroma from 'chroma-js';
 
@@ -90,27 +91,92 @@ export function testContentFunctions(t, message, fn) {
       t.matchSnapshot(result, description);
     };
 
-    evaluate.stubTemplate = name => {
+    evaluate.stubTemplate = name =>
       // Creates a particularly permissable template, allowing any slot values
       // to be stored and just outputting the contents of those slots as-are.
+      _stubTemplate(name, false);
 
-      return new (class extends html.Template {
-        #slotValues = {};
+    evaluate.stubContentFunction = name =>
+      // Like stubTemplate, but instead of a template directly, returns
+      // an object describing a content function - suitable for passing
+      // into evaluate.mock.
+      _stubTemplate(name, true);
 
-        constructor() {
-          super({
-            content: () => `${name}: ${JSON.stringify(this.#slotValues)}`,
-          });
-        }
+    const _stubTemplate = (name, mockContentFunction) => {
+      const inspectNicely = (value, opts = {}) =>
+        inspect(value, {
+          ...opts,
+          colors: false,
+          sort: true,
+        });
 
-        setSlots(slotNamesToValues) {
-          Object.assign(this.#slotValues, slotNamesToValues);
-        }
+      const makeTemplate = formatContentFn =>
+        new (class extends html.Template {
+          #slotValues = {};
 
-        setSlot(slotName, slotValue) {
-          this.#slotValues[slotName] = slotValue;
-        }
-      });
+          constructor() {
+            super({
+              content: () => this.#getContent(formatContentFn),
+            });
+          }
+
+          setSlots(slotNamesToValues) {
+            Object.assign(this.#slotValues, slotNamesToValues);
+          }
+
+          setSlot(slotName, slotValue) {
+            this.#slotValues[slotName] = slotValue;
+          }
+
+          #getContent(formatContentFn) {
+            const toInspect =
+              Object.fromEntries(
+                Object.entries(this.#slotValues)
+                  .filter(([key, value]) => value !== null));
+
+            const inspected =
+              inspectNicely(toInspect, {
+                breakLength: Infinity,
+                compact: true,
+                depth: Infinity,
+              });
+
+            return formatContentFn(inspected); `${name}: ${inspected}`;
+          }
+        });
+
+      if (mockContentFunction) {
+        return {
+          data: (...args) => ({args}),
+          generate: (data) =>
+            makeTemplate(slots => {
+              const argsLines =
+                (empty(data.args)
+                  ? []
+                  : inspectNicely(data.args, {depth: Infinity})
+                      .split('\n'));
+
+              return (`[mocked: ${name}` +
+
+                (empty(data.args)
+                  ? ``
+               : argsLines.length === 1
+                  ? `\n args: ${argsLines[0]}`
+                  : `\n args: ${argsLines[0]}\n` +
+                    argsLines.slice(1).join('\n').replace(/^/gm, ' ')) +
+
+                (!empty(data.args)
+                  ? `\n `
+                  : ` - `) +
+
+                (slots
+                  ? `slots: ${slots}]`
+                  : `slots: none]`));
+            }),
+        };
+      } else {
+        return makeTemplate(slots => `${name}: ${slots}`);
+      }
     };
 
     evaluate.mock = (...opts) => {
diff --git a/test/lib/index.js b/test/lib/index.js
index b9cc82f8..5fb5bf78 100644
--- a/test/lib/index.js
+++ b/test/lib/index.js
@@ -1,3 +1,6 @@
+Error.stackTraceLimit = Infinity;
+
 export * from './content-function.js';
 export * from './generic-mock.js';
+export * from './wiki-data.js';
 export * from './strict-match-error.js';
diff --git a/test/lib/wiki-data.js b/test/lib/wiki-data.js
new file mode 100644
index 00000000..c4083a56
--- /dev/null
+++ b/test/lib/wiki-data.js
@@ -0,0 +1,24 @@
+import {linkWikiDataArrays} from '#yaml';
+
+export function linkAndBindWikiData(wikiData) {
+  linkWikiDataArrays(wikiData);
+
+  return {
+    // Mutate to make the below functions aware of new data objects, or of
+    // reordering the existing ones. Don't mutate arrays such as trackData
+    // in-place; assign completely new arrays to this wikiData object instead.
+    wikiData,
+
+    // Use this after you've mutated wikiData to assign new data arrays.
+    // It'll automatically relink everything on wikiData so all the objects
+    // are caught up to date.
+    linkWikiDataArrays:
+      linkWikiDataArrays.bind(null, wikiData),
+
+    // Use this if you HAVEN'T mutated wikiData and just need to decache
+    // indirect dependencies on exposed properties of other data objects.
+    // See documentation on linkWikiDataArarys (in yaml.js) for more info.
+    XXX_decacheWikiData:
+      linkWikiDataArrays.bind(null, wikiData, {XXX_decacheWikiData: true}),
+  };
+}
diff --git a/test/snapshot/generateAlbumCoverArtwork.js b/test/snapshot/generateAlbumCoverArtwork.js
index 98632d39..b1c7885f 100644
--- a/test/snapshot/generateAlbumCoverArtwork.js
+++ b/test/snapshot/generateAlbumCoverArtwork.js
@@ -1,12 +1,14 @@
 import t from 'tap';
+
+import contentFunction from '#content-function';
 import {testContentFunctions} from '#test-lib';
 
 testContentFunctions(t, 'generateAlbumCoverArtwork (snapshot)', async (t, evaluate) => {
-  await evaluate.load();
-
-  const extraDependencies = {
-    getSizeOfImageFile: () => 0,
-  };
+  await evaluate.load({
+    mock: {
+      image: evaluate.stubContentFunction('image'),
+    },
+  });
 
   const album = {
     directory: 'bee-forus-seatbelt-safebee',
@@ -23,13 +25,11 @@ testContentFunctions(t, 'generateAlbumCoverArtwork (snapshot)', async (t, evalua
     name: 'generateAlbumCoverArtwork',
     args: [album],
     slots: {mode: 'primary'},
-    extraDependencies,
   });
 
   evaluate.snapshot('display: thumbnail', {
     name: 'generateAlbumCoverArtwork',
     args: [album],
     slots: {mode: 'thumbnail'},
-    extraDependencies,
   });
 });
diff --git a/test/snapshot/generateAlbumSecondaryNav.js b/test/snapshot/generateAlbumSecondaryNav.js
index a5cb2e91..709b062e 100644
--- a/test/snapshot/generateAlbumSecondaryNav.js
+++ b/test/snapshot/generateAlbumSecondaryNav.js
@@ -6,8 +6,8 @@ testContentFunctions(t, 'generateAlbumSecondaryNav (snapshot)', async (t, evalua
 
   let album, group1, group2;
 
-  group1 = {name: 'VCG', directory: 'vcg'};
-  group2 = {name: 'Bepis', directory: 'bepis'};
+  group1 = {name: 'VCG', directory: 'vcg', color: '#abcdef'};
+  group2 = {name: 'Bepis', directory: 'bepis', color: '#123456'};
 
   album = {
     date: new Date('2010-04-13'),
diff --git a/test/snapshot/generateCoverArtwork.js b/test/snapshot/generateCoverArtwork.js
index 21c91454..e35dd8d0 100644
--- a/test/snapshot/generateCoverArtwork.js
+++ b/test/snapshot/generateCoverArtwork.js
@@ -2,11 +2,11 @@ import t from 'tap';
 import {testContentFunctions} from '#test-lib';
 
 testContentFunctions(t, 'generateCoverArtwork (snapshot)', async (t, evaluate) => {
-  await evaluate.load();
-
-  const extraDependencies = {
-    getSizeOfImageFile: () => 0,
-  };
+  await evaluate.load({
+    mock: {
+      image: evaluate.stubContentFunction('image', {mock: true}),
+    },
+  });
 
   const artTags = [
     {name: 'Damara', directory: 'damara', isContentWarning: false},
@@ -21,13 +21,11 @@ testContentFunctions(t, 'generateCoverArtwork (snapshot)', async (t, evaluate) =
     name: 'generateCoverArtwork',
     args: [artTags],
     slots: {path, mode: 'primary'},
-    extraDependencies,
   });
 
   evaluate.snapshot('display: thumbnail', {
     name: 'generateCoverArtwork',
     args: [artTags],
     slots: {path, mode: 'thumbnail'},
-    extraDependencies,
   });
 });
diff --git a/test/snapshot/generateTrackCoverArtwork.js b/test/snapshot/generateTrackCoverArtwork.js
index 9e154703..03a181e7 100644
--- a/test/snapshot/generateTrackCoverArtwork.js
+++ b/test/snapshot/generateTrackCoverArtwork.js
@@ -2,11 +2,11 @@ import t from 'tap';
 import {testContentFunctions} from '#test-lib';
 
 testContentFunctions(t, 'generateTrackCoverArtwork (snapshot)', async (t, evaluate) => {
-  await evaluate.load();
-
-  const extraDependencies = {
-    getSizeOfImageFile: () => 0,
-  };
+  await evaluate.load({
+    mock: {
+      image: evaluate.stubContentFunction('image'),
+    },
+  });
 
   const album = {
     directory: 'bee-forus-seatbelt-safebee',
@@ -37,27 +37,23 @@ testContentFunctions(t, 'generateTrackCoverArtwork (snapshot)', async (t, evalua
     name: 'generateTrackCoverArtwork',
     args: [track1],
     slots: {mode: 'primary'},
-    extraDependencies,
   });
 
   evaluate.snapshot('display: thumbnail - unique art', {
     name: 'generateTrackCoverArtwork',
     args: [track1],
     slots: {mode: 'thumbnail'},
-    extraDependencies,
   });
 
   evaluate.snapshot('display: primary - no unique art', {
     name: 'generateTrackCoverArtwork',
     args: [track2],
     slots: {mode: 'primary'},
-    extraDependencies,
   });
 
   evaluate.snapshot('display: thumbnail - no unique art', {
     name: 'generateTrackCoverArtwork',
     args: [track2],
     slots: {mode: 'thumbnail'},
-    extraDependencies,
   });
 });
diff --git a/test/snapshot/image.js b/test/snapshot/image.js
index 6bec1cca..2a1e9805 100644
--- a/test/snapshot/image.js
+++ b/test/snapshot/image.js
@@ -4,11 +4,18 @@ import {testContentFunctions} from '#test-lib';
 testContentFunctions(t, 'image (snapshot)', async (t, evaluate) => {
   await evaluate.load();
 
-  const quickSnapshot = (message, opts) =>
+  const quickSnapshot = (message, {extraDependencies, ...opts}) =>
     evaluate.snapshot(message, {
       name: 'image',
       extraDependencies: {
-        getSizeOfImageFile: () => 0,
+        checkIfImagePathHasCachedThumbnails: path => !path.endsWith('.gif'),
+        getSizeOfImagePath: () => 0,
+        getDimensionsOfImagePath: () => [600, 600],
+        getThumbnailEqualOrSmaller: () => 'medium',
+        getThumbnailsAvailableForDimensions: () =>
+          [['large', 800], ['medium', 400], ['small', 250]],
+        missingImagePaths: ['album-art/missing/cover.png'],
+        ...extraDependencies,
       },
       ...opts,
     });
@@ -79,7 +86,7 @@ testContentFunctions(t, 'image (snapshot)', async (t, evaluate) => {
 
   quickSnapshot('link with file size', {
     extraDependencies: {
-      getSizeOfImageFile: () => 10 ** 6,
+      getSizeOfImagePath: () => 10 ** 6,
     },
     slots: {
       path: ['media.albumCover', 'pingas', 'png'],
@@ -98,4 +105,44 @@ testContentFunctions(t, 'image (snapshot)', async (t, evaluate) => {
       path: ['media.albumCover', 'beyond-canon', 'png'],
     },
   });
+
+  evaluate.snapshot('thumbnail details', {
+    name: 'image',
+    extraDependencies: {
+      checkIfImagePathHasCachedThumbnails: () => true,
+      getSizeOfImagePath: () => 0,
+      getDimensionsOfImagePath: () => [900, 1200],
+      getThumbnailsAvailableForDimensions: () =>
+        [['voluminous', 1200], ['middling', 900], ['petite', 20]],
+      getThumbnailEqualOrSmaller: () => 'voluminous',
+      missingImagePaths: [],
+    },
+    slots: {
+      thumb: 'gargantuan',
+      path: ['media.albumCover', 'beyond-canon', 'png'],
+    },
+  });
+
+  quickSnapshot('thumb requested but source is gif', {
+    slots: {
+      thumb: 'medium',
+      path: ['media.flashArt', '5426', 'gif'],
+    },
+  });
+
+  quickSnapshot('missing image path', {
+    slots: {
+      thumb: 'medium',
+      path: ['media.albumCover', 'missing', 'png'],
+      link: true,
+    },
+  });
+
+  quickSnapshot('missing image path w/ missingSourceContent', {
+    slots: {
+      thumb: 'medium',
+      path: ['media.albumCover', 'missing', 'png'],
+      missingSourceContent: `Cover's missing, whoops`,
+    },
+  });
 });
diff --git a/test/snapshot/linkThing.js b/test/snapshot/linkThing.js
new file mode 100644
index 00000000..195d8c0e
--- /dev/null
+++ b/test/snapshot/linkThing.js
@@ -0,0 +1,87 @@
+import t from 'tap';
+import * as html from '#html';
+import {testContentFunctions} from '#test-lib';
+
+testContentFunctions(t, 'linkThing (snapshot)', async (t, evaluate) => {
+  await evaluate.load();
+
+  const quickSnapshot = (message, oneOrMultiple) =>
+    evaluate.snapshot(message,
+      (Array.isArray(oneOrMultiple)
+        ? {name: 'linkThing', multiple: oneOrMultiple}
+        : {name: 'linkThing', ...oneOrMultiple}));
+
+  quickSnapshot('basic behavior', {
+    args: ['localized.track', {
+      directory: 'foo',
+      color: '#abcdef',
+      name: `Cool track!`,
+    }],
+  });
+
+  quickSnapshot('preferShortName', {
+    args: ['localized.tag', {
+      directory: 'five-oceanfalls',
+      name: 'Five (Oceanfalls)',
+      nameShort: 'Five',
+    }],
+    slots: {preferShortName: true},
+  });
+
+  quickSnapshot('tooltip & content', {
+    args: ['localized.album', {
+      directory: 'beyond-canon',
+      name: 'Beyond Canon',
+    }],
+    multiple: [
+      {slots: {tooltip: false}},
+      {slots: {tooltip: true}},
+      {slots: {tooltip: true, content: 'Next'}},
+      {slots: {tooltip: 'Apple', content: 'Banana'}},
+      {slots: {content: 'Banana'}},
+    ],
+  });
+
+  quickSnapshot('color', {
+    args: ['localized.track', {
+      directory: 'showtime-piano-refrain',
+      name: 'Showtime (Piano Refrain)',
+      color: '#38f43d',
+    }],
+    multiple: [
+      {slots: {color: false}},
+      {slots: {color: true}},
+      {slots: {color: '#aaccff'}},
+    ],
+  });
+
+  quickSnapshot('tags in name escaped', [
+    {args: ['localized.track', {
+      directory: 'foo',
+      name: `<a href="SNOOPING">AS USUAL</a> I SEE`,
+    }]},
+    {args: ['localized.track', {
+      directory: 'bar',
+      name: `<b>boldface</b>`,
+    }]},
+    {args: ['localized.album', {
+      directory: 'exile',
+      name: '>Exile<',
+    }]},
+    {args: ['localized.track', {
+      directory: 'heart',
+      name: '<3',
+    }]},
+  ]);
+
+  quickSnapshot('nested links in content stripped', {
+    args: ['localized.staticPage', {directory: 'foo', name: 'Foo'}],
+    slots: {
+      content:
+        html.tag('b', {[html.joinChildren]: ''}, [
+          html.tag('a', {href: 'bar'}, `Oooo!`),
+          ` Very spooky.`,
+        ]),
+    },
+  });
+});
diff --git a/test/snapshot/transformContent.js b/test/snapshot/transformContent.js
index 25952856..b05beac1 100644
--- a/test/snapshot/transformContent.js
+++ b/test/snapshot/transformContent.js
@@ -2,7 +2,11 @@ import t from 'tap';
 import {testContentFunctions} from '#test-lib';
 
 testContentFunctions(t, 'transformContent (snapshot)', async (t, evaluate) => {
-  await evaluate.load();
+  await evaluate.load({
+    mock: {
+      image: evaluate.stubContentFunction('image'),
+    },
+  });
 
   const extraDependencies = {
     wikiData: {
@@ -11,8 +15,6 @@ testContentFunctions(t, 'transformContent (snapshot)', async (t, evaluate) => {
       ],
     },
 
-    getSizeOfImageFile: () => 0,
-
     to: (key, ...args) => `to-${key}/${args.join('/')}`,
   };
 
@@ -50,15 +52,18 @@ testContentFunctions(t, 'transformContent (snapshot)', async (t, evaluate) => {
 
   quickSnapshot(
     'non-inline image #2',
-      `Rad.\n<img src="spark.png">`);
+      `Rad.\n` +
+      `<img src="spark.png">`);
 
   quickSnapshot(
     'non-inline image #3',
-      `<img src="spark.png">\nBaller.`);
+      `<img src="spark.png">\n` +
+      `Baller.`);
 
   quickSnapshot(
     'dates',
-      `[[date:2023-04-13]] Yep!\nVery nice: [[date:25 October 2413]]`);
+      `[[date:2023-04-13]] Yep!\n` +
+      `Very nice: [[date:25 October 2413]]`);
 
   quickSnapshot(
     'super basic string',
diff --git a/test/unit/data/things/cacheable-object.js b/test/unit/data/cacheable-object.js
index 2e82af08..57e562d8 100644
--- a/test/unit/data/things/cacheable-object.js
+++ b/test/unit/data/cacheable-object.js
@@ -195,13 +195,10 @@ t.test(`CacheableObject validate on update`, t => {
   obj.directory = 'megalovania';
   t.equal(obj.directory, 'megalovania');
 
-  try {
-    obj.directory = 25;
-  } catch (err) {
-    thrownError = err;
-  }
+  t.throws(
+    () => { obj.directory = 25; },
+    {cause: mockError});
 
-  t.equal(thrownError, mockError);
   t.equal(obj.directory, 'megalovania');
 
   const date = new Date(`25 December 2009`);
@@ -209,13 +206,10 @@ t.test(`CacheableObject validate on update`, t => {
   obj.date = date;
   t.equal(obj.date, date);
 
-  try {
-    obj.date = `TWELFTH PERIGEE'S EVE`;
-  } catch (err) {
-    thrownError = err;
-  }
+  t.throws(
+    () => { obj.date = `TWELFTH PERIGEE'S EVE`; },
+    {cause: TypeError});
 
-  t.equal(thrownError?.constructor, TypeError);
   t.equal(obj.date, date);
 });
 
@@ -244,8 +238,8 @@ t.test(`CacheableObject default property throws if invalid`, t => {
 
   let thrownError;
 
-  try {
-    newCacheableObject({
+  t.throws(
+    () => newCacheableObject({
       string: {
         flags: {
           update: true
@@ -261,10 +255,6 @@ t.test(`CacheableObject default property throws if invalid`, t => {
           }
         }
       }
-    });
-  } catch (err) {
-    thrownError = err;
-  }
-
-  t.equal(thrownError, mockError);
+    }),
+    {cause: mockError});
 });
diff --git a/test/unit/data/composite/control-flow/exposeConstant.js b/test/unit/data/composite/control-flow/exposeConstant.js
new file mode 100644
index 00000000..0c75894b
--- /dev/null
+++ b/test/unit/data/composite/control-flow/exposeConstant.js
@@ -0,0 +1,42 @@
+import t from 'tap';
+
+import {compositeFrom, continuationSymbol, input} from '#composite';
+import {exposeConstant} from '#composite/control-flow';
+
+t.test(`exposeConstant: basic behavior`, t => {
+  t.plan(2);
+
+  const composite1 = compositeFrom({
+    compose: false,
+
+    steps: [
+      exposeConstant({
+        value: input.value('foo'),
+      }),
+    ],
+  });
+
+  t.match(composite1, {
+    expose: {
+      dependencies: [],
+    },
+  });
+
+  t.equal(composite1.expose.compute(), 'foo');
+});
+
+t.test(`exposeConstant: validate inputs`, t => {
+  t.plan(2);
+
+  t.throws(
+    () => exposeConstant({}),
+    {message: `Errors in input options passed to exposeConstant`, errors: [
+      {message: `Required these inputs: value`},
+    ]});
+
+  t.throws(
+    () => exposeConstant({value: 'some dependency'}),
+    {message: `Errors in input options passed to exposeConstant`, errors: [
+      {message: `value: Expected input.value() call, got dependency name`},
+    ]});
+});
diff --git a/test/unit/data/composite/control-flow/exposeDependency.js b/test/unit/data/composite/control-flow/exposeDependency.js
new file mode 100644
index 00000000..8f6bfd01
--- /dev/null
+++ b/test/unit/data/composite/control-flow/exposeDependency.js
@@ -0,0 +1,64 @@
+import t from 'tap';
+
+import {compositeFrom, continuationSymbol, input} from '#composite';
+import {exposeDependency} from '#composite/control-flow';
+
+t.test(`exposeDependency: basic behavior`, t => {
+  t.plan(4);
+
+  const composite1 = compositeFrom({
+    compose: false,
+
+    steps: [
+      exposeDependency({dependency: 'foo'}),
+    ],
+  });
+
+  t.match(composite1, {
+    expose: {
+      dependencies: ['foo'],
+    },
+  });
+
+  t.equal(composite1.expose.compute({foo: 'bar'}), 'bar');
+
+  const composite2 = compositeFrom({
+    compose: false,
+
+    steps: [
+      {
+        dependencies: ['foo'],
+        compute: (continuation, {foo}) =>
+          continuation({'#bar': foo.toUpperCase()}),
+      },
+
+      exposeDependency({dependency: '#bar'}),
+    ],
+  });
+
+  t.match(composite2, {
+    expose: {
+      dependencies: ['foo'],
+    },
+  });
+
+  t.equal(composite2.expose.compute({foo: 'bar'}), 'BAR');
+});
+
+t.test(`exposeDependency: validate inputs`, t => {
+  t.plan(2);
+
+  t.throws(
+    () => exposeDependency({}),
+    {message: `Errors in input options passed to exposeDependency`, errors: [
+      {message: `Required these inputs: dependency`},
+    ]});
+
+  t.throws(
+    () => exposeDependency({
+      dependency: input.value('some static value'),
+    }),
+    {message: `Errors in input options passed to exposeDependency`, errors: [
+      {message: `dependency: Expected dependency name, got input.value() call`},
+    ]});
+});
diff --git a/test/unit/data/composite/control-flow/withResultOfAvailabilityCheck.js b/test/unit/data/composite/control-flow/withResultOfAvailabilityCheck.js
new file mode 100644
index 00000000..2bcabb4f
--- /dev/null
+++ b/test/unit/data/composite/control-flow/withResultOfAvailabilityCheck.js
@@ -0,0 +1,195 @@
+import t from 'tap';
+
+import {compositeFrom, continuationSymbol, input} from '#composite';
+import {withResultOfAvailabilityCheck} from '#composite/control-flow';
+
+const composite = compositeFrom({
+  compose: false,
+
+  steps: [
+    withResultOfAvailabilityCheck({
+      from: 'from',
+      mode: 'mode',
+    }).outputs({
+      ['#availability']: '#result',
+    }),
+
+    {
+      dependencies: ['#result'],
+      compute: ({'#result': result}) => result,
+    },
+  ],
+});
+
+t.test(`withResultOfAvailabilityCheck: basic behavior`, t => {
+  t.plan(1);
+
+  t.match(composite, {
+    expose: {
+      dependencies: ['from', 'mode'],
+    },
+  });
+});
+
+const quickCompare = (t, expect, {from, mode}) =>
+  t.equal(composite.expose.compute({from, mode}), expect);
+
+const quickThrows = (t, {from, mode}) =>
+  t.throws(() => composite.expose.compute({from, mode}));
+
+t.test(`withResultOfAvailabilityCheck: mode = null`, t => {
+  t.plan(11);
+
+  quickCompare(t, true,  {mode: 'null', from: 'truthy string'});
+  quickCompare(t, true,  {mode: 'null', from: 123});
+  quickCompare(t, true,  {mode: 'null', from: true});
+
+  quickCompare(t, true,  {mode: 'null', from: ''});
+  quickCompare(t, true,  {mode: 'null', from: 0});
+  quickCompare(t, true,  {mode: 'null', from: -1});
+  quickCompare(t, true,  {mode: 'null', from: false});
+
+  quickCompare(t, true,  {mode: 'null', from: [1, 2, 3]});
+  quickCompare(t, true,  {mode: 'null', from: []});
+
+  quickCompare(t, false, {mode: 'null', from: null});
+  quickCompare(t, false, {mode: 'null', from: undefined});
+});
+
+t.test(`withResultOfAvailabilityCheck: mode = empty`, t => {
+  t.plan(11);
+
+  quickThrows(t, {mode: 'empty', from: 'truthy string'});
+  quickThrows(t, {mode: 'empty', from: 123});
+  quickThrows(t, {mode: 'empty', from: true});
+
+  quickThrows(t, {mode: 'empty', from: ''});
+  quickThrows(t, {mode: 'empty', from: 0});
+  quickThrows(t, {mode: 'empty', from: -1});
+  quickThrows(t, {mode: 'empty', from: false});
+
+  quickCompare(t, true,  {mode: 'empty', from: [1, 2, 3]});
+  quickCompare(t, false, {mode: 'empty', from: []});
+
+  quickCompare(t, false, {mode: 'empty', from: null});
+  quickCompare(t, false, {mode: 'empty', from: undefined});
+});
+
+t.test(`withResultOfAvailabilityCheck: mode = falsy`, t => {
+  t.plan(11);
+
+  quickCompare(t, true,  {mode: 'falsy', from: 'truthy string'});
+  quickCompare(t, true,  {mode: 'falsy', from: 123});
+  quickCompare(t, true,  {mode: 'falsy', from: true});
+
+  quickCompare(t, false, {mode: 'falsy', from: ''});
+  quickCompare(t, false, {mode: 'falsy', from: 0});
+  quickCompare(t, true,  {mode: 'falsy', from: -1});
+  quickCompare(t, false, {mode: 'falsy', from: false});
+
+  quickCompare(t, true,  {mode: 'falsy', from: [1, 2, 3]});
+  quickCompare(t, false, {mode: 'falsy', from: []});
+
+  quickCompare(t, false, {mode: 'falsy', from: null});
+  quickCompare(t, false, {mode: 'falsy', from: undefined});
+});
+
+t.test(`withResultOfAvailabilityCheck: mode = index`, t => {
+  t.plan(11);
+
+  quickCompare(t, false, {mode: 'index', from: 'truthy string'});
+  quickCompare(t, true,  {mode: 'index', from: 123});
+  quickCompare(t, false, {mode: 'index', from: true});
+
+  quickCompare(t, false, {mode: 'index', from: ''});
+  quickCompare(t, true,  {mode: 'index', from: 0});
+  quickCompare(t, false, {mode: 'index', from: -1});
+  quickCompare(t, false, {mode: 'index', from: false});
+
+  quickCompare(t, false, {mode: 'index', from: [1, 2, 3]});
+  quickCompare(t, false, {mode: 'index', from: []});
+
+  quickCompare(t, false, {mode: 'index', from: null});
+  quickCompare(t, false, {mode: 'index', from: undefined});
+});
+
+t.test(`withResultOfAvailabilityCheck: default mode`, t => {
+  t.plan(1);
+
+  const template = withResultOfAvailabilityCheck({
+    from: 'foo',
+  });
+
+  t.match(template.toDescription(), {
+    inputMapping: {
+      from: input.dependency('foo'),
+      mode: input.value('null'),
+    },
+  });
+});
+
+t.test(`withResultOfAvailabilityCheck: validate static inputs`, t => {
+  t.plan(5);
+
+  t.throws(
+    () => withResultOfAvailabilityCheck({}),
+    {message: `Errors in input options passed to withResultOfAvailabilityCheck`, errors: [
+      {message: `Required these inputs: from`},
+    ]});
+
+  t.doesNotThrow(() =>
+    withResultOfAvailabilityCheck({
+      from: 'dependency1',
+      mode: 'dependency2',
+    }));
+
+  t.doesNotThrow(() =>
+    withResultOfAvailabilityCheck({
+      from: input.value('some static value'),
+      mode: input.value('null'),
+    }));
+
+  t.throws(
+    () => withResultOfAvailabilityCheck({
+      from: 'foo',
+      mode: input.value('invalid'),
+    }),
+    {message: `Errors in input options passed to withResultOfAvailabilityCheck`, errors: [
+      {message: `mode: Expected one of null empty falsy index, got invalid`},
+    ]});
+
+  t.throws(() =>
+    withResultOfAvailabilityCheck({
+      from: input.value(null),
+      mode: input.value(null),
+    }),
+    {message: `Errors in input options passed to withResultOfAvailabilityCheck`, errors: [
+      {message: `mode: Expected a value, got null`},
+    ]});
+});
+
+t.test(`withResultOfAvailabilityCheck: validate dynamic inputs`, t => {
+  t.plan(2);
+
+  t.throws(
+    () => composite.expose.compute({
+      from: 'apple',
+      mode: 'banana',
+    }),
+    {message: `Error computing composition`, cause:
+      {message: `Error computing composition withResultOfAvailabilityCheck`, cause:
+        {message: `Errors in input values provided to withResultOfAvailabilityCheck`, errors: [
+          {message: `mode: Expected one of null empty falsy index, got banana`},
+        ]}}});
+
+  t.throws(
+    () => composite.expose.compute({
+      from: null,
+      mode: null,
+    }),
+    {message: `Error computing composition`, cause:
+      {message: `Error computing composition withResultOfAvailabilityCheck`, cause:
+        {message: `Errors in input values provided to withResultOfAvailabilityCheck`, errors: [
+          {message: `mode: Expected a value, got null`},
+        ]}}});
+});
diff --git a/test/unit/data/composite/data/withPropertiesFromObject.js b/test/unit/data/composite/data/withPropertiesFromObject.js
new file mode 100644
index 00000000..ead1b9b2
--- /dev/null
+++ b/test/unit/data/composite/data/withPropertiesFromObject.js
@@ -0,0 +1,248 @@
+import t from 'tap';
+
+import {compositeFrom, input} from '#composite';
+import {exposeDependency} from '#composite/control-flow';
+import {withPropertiesFromObject} from '#composite/data';
+
+const composite = compositeFrom({
+  compose: false,
+
+  steps: [
+    withPropertiesFromObject({
+      object: 'object',
+      properties: 'properties',
+    }),
+
+    exposeDependency({dependency: '#object'}),
+  ],
+});
+
+t.test(`withPropertiesFromObject: basic behavior`, t => {
+  t.plan(4);
+
+  t.match(composite, {
+    expose: {
+      dependencies: ['object', 'properties'],
+    },
+  });
+
+  t.same(
+    composite.expose.compute({
+      object: {foo: 'bar', bim: 'BOOM', bam: 'baz'},
+      properties: ['foo', 'bim'],
+    }),
+    {foo: 'bar', bim: 'BOOM'});
+
+  t.same(
+    composite.expose.compute({
+      object: {value1: 'uwah', value2: 'arah'},
+      properties: ['value1', 'value3'],
+    }),
+    {value1: 'uwah', value3: null});
+
+  t.same(
+    composite.expose.compute({
+      object: null,
+      properties: ['ohMe', 'ohMy', 'ohDear'],
+    }),
+    {ohMe: null, ohMy: null, ohDear: null});
+});
+
+t.test(`withPropertiesFromObject: output shapes & values`, t => {
+  t.plan(2 * 2 * 3 ** 2);
+
+  const dependencies = {
+    ['object_dependency']:
+      {foo: 'apple', bar: 'banana', baz: 'orange'},
+    [input('object_neither')]:
+      {foo: 'koala', bar: 'okapi', baz: 'mongoose'},
+    ['properties_dependency']:
+      ['foo', 'bar', 'missing1'],
+    [input('properties_neither')]:
+      ['foo', 'baz', 'missing3'],
+  };
+
+  const mapLevel1 = [
+    [input.value('prefix_value'), [
+      ['object_dependency', [
+        ['properties_dependency', {
+          '#object': {foo: 'apple', bar: 'banana', missing1: null},
+        }],
+        [input.value(['bar', 'baz', 'missing2']), {
+          '#prefix_value.bar': 'banana',
+          '#prefix_value.baz': 'orange',
+          '#prefix_value.missing2': null,
+        }],
+        [input('properties_neither'), {
+          '#object': {foo: 'apple', baz: 'orange', missing3: null},
+        }]]],
+
+      [input.value({foo: 'ouh', bar: 'rah', baz: 'nyu'}), [
+        ['properties_dependency', {
+          '#object': {foo: 'ouh', bar: 'rah', missing1: null},
+        }],
+        [input.value(['bar', 'baz', 'missing2']), {
+          '#prefix_value.bar': 'rah',
+          '#prefix_value.baz': 'nyu',
+          '#prefix_value.missing2': null,
+        }],
+        [input('properties_neither'), {
+          '#object': {foo: 'ouh', baz: 'nyu', missing3: null},
+        }]]],
+
+      [input('object_neither'), [
+        ['properties_dependency', {
+          '#object': {foo: 'koala', bar: 'okapi', missing1: null},
+        }],
+        [input.value(['bar', 'baz', 'missing2']), {
+          '#prefix_value.bar': 'okapi',
+          '#prefix_value.baz': 'mongoose',
+          '#prefix_value.missing2': null,
+        }],
+        [input('properties_neither'), {
+          '#object': {foo: 'koala', baz: 'mongoose', missing3: null},
+        }]]]]],
+
+    [input.value(null), [
+      ['object_dependency', [
+        ['properties_dependency', {
+          '#object': {foo: 'apple', bar: 'banana', missing1: null},
+        }],
+        [input.value(['bar', 'baz', 'missing2']), {
+          '#object_dependency.bar': 'banana',
+          '#object_dependency.baz': 'orange',
+          '#object_dependency.missing2': null,
+        }],
+        [input('properties_neither'), {
+          '#object': {foo: 'apple', baz: 'orange', missing3: null},
+        }]]],
+
+      [input.value({foo: 'ouh', bar: 'rah', baz: 'nyu'}), [
+        ['properties_dependency', {
+          '#object': {foo: 'ouh', bar: 'rah', missing1: null},
+        }],
+        [input.value(['bar', 'baz', 'missing2']), {
+          '#object.bar': 'rah',
+          '#object.baz': 'nyu',
+          '#object.missing2': null,
+        }],
+        [input('properties_neither'), {
+          '#object': {foo: 'ouh', baz: 'nyu', missing3: null},
+        }]]],
+
+      [input('object_neither'), [
+        ['properties_dependency', {
+          '#object': {foo: 'koala', bar: 'okapi', missing1: null},
+        }],
+        [input.value(['bar', 'baz', 'missing2']), {
+          '#object.bar': 'okapi',
+          '#object.baz': 'mongoose',
+          '#object.missing2': null,
+        }],
+        [input('properties_neither'), {
+          '#object': {foo: 'koala', baz: 'mongoose', missing3: null},
+        }]]]]],
+  ];
+
+  for (const [prefixInput, mapLevel2] of mapLevel1) {
+    for (const [objectInput, mapLevel3] of mapLevel2) {
+      for (const [propertiesInput, outputDict] of mapLevel3) {
+        const step = withPropertiesFromObject({
+          prefix: prefixInput,
+          object: objectInput,
+          properties: propertiesInput,
+        });
+
+        quickCheckOutputs(step, outputDict);
+      }
+    }
+  }
+
+  function quickCheckOutputs(step, outputDict) {
+    t.same(
+      Object.keys(step.toDescription().outputs),
+      Object.keys(outputDict));
+
+    const composite = compositeFrom({
+      compose: false,
+      steps: [step, {
+        dependencies: Object.keys(outputDict),
+        compute: dependencies => dependencies,
+      }],
+    });
+
+    t.same(
+      composite.expose.compute(dependencies),
+      outputDict);
+  }
+});
+
+t.test(`withPropertiesFromObject: validate static inputs`, t => {
+  t.plan(3);
+
+  t.throws(
+    () => withPropertiesFromObject({}),
+    {message: `Errors in input options passed to withPropertiesFromObject`, errors: [
+      {message: `Required these inputs: object, properties`},
+    ]});
+
+  t.throws(
+    () => withPropertiesFromObject({
+      object: input.value('intriguing'),
+      properties: input.value('very'),
+      prefix: input.value({yes: 'yup'}),
+    }),
+    {message: `Errors in input options passed to withPropertiesFromObject`, errors: [
+      {message: `object: Expected an object, got string`},
+      {message: `properties: Expected an array, got string`},
+      {message: `prefix: Expected a string, got object`},
+    ]});
+
+  t.throws(
+    () => withPropertiesFromObject({
+      object: input.value([['abc', 1], ['def', 2], [123, 3]]),
+      properties: input.value(['abc', 'def', 123]),
+    }),
+    {message: `Errors in input options passed to withPropertiesFromObject`, errors: [
+      {message: `object: Expected an object, got array`},
+      {message: `properties: Errors validating array items`, errors: [
+        {
+          [Symbol.for('hsmusic.decorate.indexInSourceArray')]: 2,
+          message: /Expected a string, got number/,
+        },
+      ]},
+    ]});
+});
+
+t.test(`withPropertiesFromObject: validate dynamic inputs`, t => {
+  t.plan(2);
+
+  t.throws(
+    () => composite.expose.compute({
+      object: 'intriguing',
+      properties: 'onceMore',
+    }),
+    {message: `Error computing composition`, cause:
+      {message: `Error computing composition withPropertiesFromObject`, cause:
+        {message: `Errors in input values provided to withPropertiesFromObject`, errors: [
+          {message: `object: Expected an object, got string`},
+          {message: `properties: Expected an array, got string`},
+        ]}}});
+
+  t.throws(
+    () => composite.expose.compute({
+      object: [['abc', 1], ['def', 2], [123, 3]],
+      properties: ['abc', 'def', 123],
+    }),
+    {message: `Error computing composition`, cause:
+      {message: `Error computing composition withPropertiesFromObject`, cause:
+        {message: `Errors in input values provided to withPropertiesFromObject`, errors: [
+          {message: `object: Expected an object, got array`},
+          {message: `properties: Errors validating array items`, errors: [
+            {
+              [Symbol.for('hsmusic.decorate.indexInSourceArray')]: 2,
+              message: /Expected a string, got number/,
+            },
+          ]},
+        ]}}});
+});
diff --git a/test/unit/data/composite/data/withPropertyFromObject.js b/test/unit/data/composite/data/withPropertyFromObject.js
new file mode 100644
index 00000000..6a772c36
--- /dev/null
+++ b/test/unit/data/composite/data/withPropertyFromObject.js
@@ -0,0 +1,122 @@
+import t from 'tap';
+
+import {compositeFrom, input} from '#composite';
+import {exposeDependency} from '#composite/control-flow';
+import {withPropertyFromObject} from '#composite/data';
+
+t.test(`withPropertyFromObject: basic behavior`, t => {
+  t.plan(4);
+
+  const composite = compositeFrom({
+    compose: false,
+
+    steps: [
+      withPropertyFromObject({
+        object: 'object',
+        property: 'property',
+      }),
+
+      exposeDependency({dependency: '#value'}),
+    ],
+  });
+
+  t.match(composite, {
+    expose: {
+      dependencies: ['object', 'property'],
+    },
+  });
+
+  t.equal(composite.expose.compute({
+    object: {foo: 'bar', bim: 'BOOM'},
+    property: 'bim',
+  }), 'BOOM');
+
+  t.equal(composite.expose.compute({
+    object: {value1: 'uwah'},
+    property: 'value2',
+  }), null);
+
+  t.equal(composite.expose.compute({
+    object: null,
+    property: 'oml where did me object go',
+  }), null);
+});
+
+t.test(`withPropertyFromObject: output shapes & values`, t => {
+  t.plan(2 * 3 ** 2);
+
+  const dependencies = {
+    ['object_dependency']:
+      {foo: 'apple', bar: 'banana', baz: 'orange'},
+    [input('object_neither')]:
+      {foo: 'koala', bar: 'okapi', baz: 'mongoose'},
+    ['property_dependency']:
+      'foo',
+    [input('property_neither')]:
+      'baz',
+  };
+
+  const mapLevel1 = [
+    ['object_dependency', [
+      ['property_dependency', {
+        '#value': 'apple',
+      }],
+      [input.value('bar'), {
+        '#object_dependency.bar': 'banana',
+      }],
+      [input('property_neither'), {
+        '#value': 'orange',
+      }]]],
+
+    [input.value({foo: 'ouh', bar: 'rah', baz: 'nyu'}), [
+      ['property_dependency', {
+        '#value': 'ouh',
+      }],
+      [input.value('bar'), {
+        '#value': 'rah',
+      }],
+      [input('property_neither'), {
+        '#value': 'nyu',
+      }]]],
+
+    [input('object_neither'), [
+      ['property_dependency', {
+        '#value': 'koala',
+      }],
+      [input.value('bar'), {
+        '#value': 'okapi',
+      }],
+      [input('property_neither'), {
+        '#value': 'mongoose',
+      }]]],
+  ];
+
+  for (const [objectInput, mapLevel2] of mapLevel1) {
+    for (const [propertyInput, outputDict] of mapLevel2) {
+      const step = withPropertyFromObject({
+        object: objectInput,
+        property: propertyInput,
+      });
+
+      quickCheckOutputs(step, outputDict);
+    }
+  }
+
+  function quickCheckOutputs(step, outputDict) {
+    t.same(
+      Object.keys(step.toDescription().outputs),
+      Object.keys(outputDict));
+
+    const composite = compositeFrom({
+      compose: false,
+      steps: [step, {
+        dependencies: Object.keys(outputDict),
+        compute: dependencies => dependencies,
+      }],
+    });
+
+    t.same(
+      composite.expose.compute(dependencies),
+      outputDict);
+  }
+});
diff --git a/test/unit/data/composite/things/track/withAlbum.js b/test/unit/data/composite/things/track/withAlbum.js
new file mode 100644
index 00000000..30f8cc5d
--- /dev/null
+++ b/test/unit/data/composite/things/track/withAlbum.js
@@ -0,0 +1,144 @@
+import t from 'tap';
+
+import {compositeFrom, input} from '#composite';
+import {exposeConstant, exposeDependency} from '#composite/control-flow';
+import {withAlbum} from '#composite/things/track';
+
+t.test(`withAlbum: basic behavior`, t => {
+  t.plan(3);
+
+  const composite = compositeFrom({
+    compose: false,
+    steps: [
+      withAlbum(),
+      exposeDependency({dependency: '#album'}),
+    ],
+  });
+
+  t.match(composite, {
+    expose: {
+      dependencies: ['albumData', 'this'],
+    },
+  });
+
+  const fakeTrack1 = {directory: 'foo'};
+  const fakeTrack2 = {directory: 'bar'};
+  const fakeAlbum = {directory: 'baz', tracks: [fakeTrack1]};
+
+  t.equal(
+    composite.expose.compute({
+      albumData: [fakeAlbum],
+      this: fakeTrack1,
+    }),
+    fakeAlbum);
+
+  t.equal(
+    composite.expose.compute({
+      albumData: [fakeAlbum],
+      this: fakeTrack2,
+    }),
+    null);
+});
+
+t.test(`withAlbum: early exit conditions (notFoundMode: null)`, t => {
+  t.plan(4);
+
+  const composite = compositeFrom({
+    compose: false,
+    steps: [
+      withAlbum(),
+      exposeConstant({
+        value: input.value('bimbam'),
+      }),
+    ],
+  });
+
+  const fakeTrack1 = {directory: 'foo'};
+  const fakeTrack2 = {directory: 'bar'};
+  const fakeAlbum = {directory: 'baz', tracks: [fakeTrack1]};
+
+  t.equal(
+    composite.expose.compute({
+      albumData: [fakeAlbum],
+      this: fakeTrack1,
+    }),
+    'bimbam',
+    `does not early exit if albumData is present and contains the track`);
+
+  t.equal(
+    composite.expose.compute({
+      albumData: [fakeAlbum],
+      this: fakeTrack2,
+    }),
+    'bimbam',
+    `does not early exit if albumData is present and does not contain the track`);
+
+  t.equal(
+    composite.expose.compute({
+      albumData: [],
+      this: fakeTrack1,
+    }),
+    'bimbam',
+    `does not early exit if albumData is empty array`);
+
+  t.equal(
+    composite.expose.compute({
+      albumData: null,
+      this: fakeTrack1,
+    }),
+    null,
+    `early exits if albumData is null`);
+});
+
+t.test(`withAlbum: early exit conditions (notFoundMode: exit)`, t => {
+  t.plan(4);
+
+  const composite = compositeFrom({
+    compose: false,
+    steps: [
+      withAlbum({
+        notFoundMode: input.value('exit'),
+      }),
+
+      exposeConstant({
+        value: input.value('bimbam'),
+      }),
+    ],
+  });
+
+  const fakeTrack1 = {directory: 'foo'};
+  const fakeTrack2 = {directory: 'bar'};
+  const fakeAlbum = {directory: 'baz', tracks: [fakeTrack1]};
+
+  t.equal(
+    composite.expose.compute({
+      albumData: [fakeAlbum],
+      this: fakeTrack1,
+    }),
+    'bimbam',
+    `does not early exit if albumData is present and contains the track`);
+
+  t.equal(
+    composite.expose.compute({
+      albumData: [fakeAlbum],
+      this: fakeTrack2,
+    }),
+    null,
+    `early exits if albumData is present and does not contain the track`);
+
+  t.equal(
+    composite.expose.compute({
+      albumData: [],
+      this: fakeTrack1,
+    }),
+    null,
+    `early exits if albumData is empty array`);
+
+  t.equal(
+    composite.expose.compute({
+      albumData: null,
+      this: fakeTrack1,
+    }),
+    null,
+    `early exits if albumData is null`);
+});
diff --git a/test/unit/data/compositeFrom.js b/test/unit/data/compositeFrom.js
new file mode 100644
index 00000000..00296675
--- /dev/null
+++ b/test/unit/data/compositeFrom.js
@@ -0,0 +1,345 @@
+import t from 'tap';
+
+import {compositeFrom, continuationSymbol, input} from '#composite';
+import {isString} from '#validators';
+
+t.test(`compositeFrom: basic behavior`, t => {
+  t.plan(2);
+
+  const composite = compositeFrom({
+    annotation: `myComposite`,
+    compose: false,
+
+    steps: [
+      {
+        dependencies: ['foo'],
+        compute: (continuation, {foo}) =>
+          continuation({'#bar': foo * 2}),
+      },
+
+      {
+        dependencies: ['#bar', 'baz', 'suffix'],
+        compute: ({'#bar': bar, baz, suffix}) =>
+          baz.repeat(bar) + suffix,
+      },
+    ],
+  });
+
+  t.match(composite, {
+    annotation: `myComposite`,
+
+    flags: {expose: true, compose: false, update: false},
+
+    expose: {
+      dependencies: ['foo', 'baz', 'suffix'],
+      compute: Function,
+      transform: null,
+    },
+
+    update: null,
+  });
+
+  t.equal(
+    composite.expose.compute({
+      foo: 3,
+      baz: 'ba',
+      suffix: 'BOOM',
+    }),
+    'babababababaBOOM');
+});
+
+t.test(`compositeFrom: input-shaped step dependencies`, t => {
+  t.plan(2);
+
+  const composite = compositeFrom({
+    compose: false,
+    steps: [
+      {
+        dependencies: [
+          input.myself(),
+          input.updateValue(),
+        ],
+
+        transform: (updateValue1, {
+          [input.myself()]: me,
+          [input.updateValue()]: updateValue2,
+        }) => ({me, updateValue1, updateValue2}),
+      },
+    ],
+  });
+
+  t.match(composite, {
+    expose: {
+      dependencies: ['this'],
+      transform: Function,
+      compute: null,
+    },
+  });
+
+  const myself = {foo: 'bar'};
+
+  t.same(
+    composite.expose.transform('banana', {
+      this: myself,
+      pomelo: 'delicious',
+    }),
+    {
+      me: myself,
+      updateValue1: 'banana',
+      updateValue2: 'banana',
+    });
+});
+
+t.test(`compositeFrom: dependencies from inputs`, t => {
+  t.plan(3);
+
+  const composite = compositeFrom({
+    annotation: `myComposite`,
+
+    compose: true,
+
+    inputMapping: {
+      foo:      input('bar'),
+      pomelo:   input.value('delicious'),
+      humorous: input.dependency('#mammal'),
+      data:     input.dependency('albumData'),
+      ref:      input.updateValue(),
+    },
+
+    inputDescriptions: {
+      foo:      input(),
+      pomelo:   input(),
+      humorous: input(),
+      data:     input(),
+      ref:      input(),
+    },
+
+    steps: [
+      {
+        dependencies: [
+          input('foo'),
+          input('pomelo'),
+          input('humorous'),
+          input('data'),
+          input('ref'),
+        ],
+
+        compute: (continuation, {
+          [input('foo')]: foo,
+          [input('pomelo')]: pomelo,
+          [input('humorous')]: humorous,
+          [input('data')]: data,
+          [input('ref')]: ref,
+        }) => continuation.exit({foo, pomelo, humorous, data, ref}),
+      },
+    ],
+  });
+
+  t.match(composite, {
+    expose: {
+      dependencies: [
+        input('bar'),
+        '#mammal',
+        'albumData',
+      ],
+
+      transform: Function,
+      compute: null,
+    },
+  });
+
+  const exitData = {};
+  const continuation = {
+    exit(value) {
+      Object.assign(exitData, value);
+      return continuationSymbol;
+    },
+  };
+
+  t.equal(
+    composite.expose.transform('album:bepis', continuation, {
+      [input('bar')]: 'squid time',
+      '#mammal': 'fox',
+      'albumData': ['album1', 'album2'],
+    }),
+    continuationSymbol);
+
+  t.same(exitData, {
+    foo: 'squid time',
+    pomelo: 'delicious',
+    humorous: 'fox',
+    data: ['album1', 'album2'],
+    ref: 'album:bepis',
+  });
+});
+
+t.test(`compositeFrom: update from various sources`, t => {
+  t.plan(3);
+
+  const match = {
+    flags: {update: true, expose: true, compose: false},
+
+    update: {
+      validate: isString,
+      default: 'foo',
+    },
+
+    expose: {
+      transform: Function,
+      compute: null,
+    },
+  };
+
+  t.test(`compositeFrom: update from composition description`, t => {
+    t.plan(2);
+
+    const composite = compositeFrom({
+      compose: false,
+
+      update: {
+        validate: isString,
+        default: 'foo',
+      },
+
+      steps: [
+        {transform: (value, continuation) => continuation(value.repeat(2))},
+        {transform: (value) => `Xx_${value}_xX`},
+      ],
+    });
+
+    t.match(composite, match);
+    t.equal(composite.expose.transform('foo'), `Xx_foofoo_xX`);
+  });
+
+  t.test(`compositeFrom: update from step dependencies`, t => {
+    t.plan(2);
+
+    const composite = compositeFrom({
+      compose: false,
+
+      steps: [
+        {
+          dependencies: [
+            input.updateValue({
+              validate: isString,
+              default: 'foo',
+            }),
+          ],
+
+          compute: ({
+            [input.updateValue()]: value,
+          }) => `Xx_${value.repeat(2)}_xX`,
+        },
+      ],
+    });
+
+    t.match(composite, match);
+    t.equal(composite.expose.transform('foo'), 'Xx_foofoo_xX');
+  });
+
+  t.test(`compositeFrom: update from inputs`, t => {
+    t.plan(3);
+
+    const composite = compositeFrom({
+      inputMapping: {
+        myInput: input.updateValue({
+          validate: isString,
+          default: 'foo',
+        }),
+      },
+
+      inputDescriptions: {
+        myInput: input(),
+      },
+
+      steps: [
+        {
+          dependencies: [input('myInput')],
+          compute: (continuation, {
+            [input('myInput')]: value,
+          }) => continuation({
+            '#value': `Xx_${value.repeat(2)}_xX`,
+          }),
+        },
+
+        {
+          dependencies: ['#value'],
+          transform: (_value, continuation, {'#value': value}) =>
+            continuation(value),
+        },
+      ],
+    });
+
+    let continuationValue = null;
+    const continuation = value => {
+      continuationValue = value;
+      return continuationSymbol;
+    };
+
+    t.match(composite, {
+      ...match,
+
+      flags: {update: true, expose: true, compose: true},
+    });
+
+    t.equal(
+      composite.expose.transform('foo', continuation),
+      continuationSymbol);
+
+    t.equal(continuationValue, 'Xx_foofoo_xX');
+  });
+});
+
+t.test(`compositeFrom: dynamic input validation from type`, t => {
+  t.plan(2);
+
+  const composite = compositeFrom({
+    inputMapping: {
+      string:   input('string'),
+      number:   input('number'),
+      boolean:  input('boolean'),
+      function: input('function'),
+      object:   input('object'),
+      array:    input('array'),
+    },
+
+    inputDescriptions: {
+      string:   input({null: true, type: 'string'}),
+      number:   input({null: true, type: 'number'}),
+      boolean:  input({null: true, type: 'boolean'}),
+      function: input({null: true, type: 'function'}),
+      object:   input({null: true, type: 'object'}),
+      array:    input({null: true, type: 'array'}),
+    },
+
+    outputs: {'#result': '#result'},
+
+    steps: [
+      {compute: continuation => continuation({'#result': 'OK'})},
+    ],
+  });
+
+  const notCalledSymbol = Symbol('continuation not called');
+
+  let continuationValue;
+  const continuation = value => {
+    continuationValue = value;
+    return continuationSymbol;
+  };
+
+  let thrownError;
+
+  try {
+    continuationValue = notCalledSymbol;
+    thrownError = null;
+    composite.expose.compute(continuation, {
+      [input('string')]: 123,
+    });
+  } catch (error) {
+    thrownError = error;
+  }
+
+  t.equal(continuationValue, notCalledSymbol);
+  t.match(thrownError, {
+  });
+});
diff --git a/test/unit/data/templateCompositeFrom.js b/test/unit/data/templateCompositeFrom.js
new file mode 100644
index 00000000..2de18730
--- /dev/null
+++ b/test/unit/data/templateCompositeFrom.js
@@ -0,0 +1,209 @@
+import t from 'tap';
+
+import {isString} from '#validators';
+
+import {
+  compositeFrom,
+  continuationSymbol,
+  input,
+  templateCompositeFrom,
+} from '#composite';
+
+t.test(`templateCompositeFrom: basic behavior`, t => {
+  t.plan(1);
+
+  const myCoolUtility = templateCompositeFrom({
+    annotation: `myCoolUtility`,
+
+    inputs: {
+      foo: input(),
+    },
+
+    outputs: ['#bar'],
+
+    steps: () => [
+      {
+        dependencies: [input('foo')],
+        compute: (continuation, {
+          [input('foo')]: foo,
+        }) => continuation({
+          ['#bar']: (typeof foo).toUpperCase()
+        }),
+      },
+    ],
+  });
+
+  const instantiatedTemplate = myCoolUtility({
+    foo: 'color',
+  });
+
+  t.match(instantiatedTemplate.toDescription(), {
+    annotation: `myCoolUtility`,
+
+    inputMapping: {
+      foo: input.dependency('color'),
+    },
+
+    inputDescriptions: {
+      foo: input(),
+    },
+
+    outputs: {
+      '#bar': '#bar',
+    },
+
+    steps: Function,
+  });
+});
+
+t.test(`templateCompositeFrom: validate static input values`, t => {
+  t.plan(3);
+
+  const stub = {
+    annotation: 'stubComposite',
+    outputs: ['#result'],
+    steps: () => [{compute: continuation => continuation({'#result': 'OK'})}],
+  };
+
+  const quickThrows = (t, composite, inputOptions, ...errorMessages) =>
+    t.throws(
+      () => composite(inputOptions),
+      {
+        message: `Errors in input options passed to stubComposite`,
+        errors: errorMessages.map(message => ({message})),
+      });
+
+  t.test(`templateCompositeFrom: validate input token shapes`, t => {
+    t.plan(15);
+
+    const template1 = templateCompositeFrom({
+      ...stub, inputs: {
+        foo: input(),
+      },
+    });
+
+    t.doesNotThrow(
+      () => template1({foo: 'dependency'}));
+
+    t.doesNotThrow(
+      () => template1({foo: input.dependency('dependency')}));
+
+    t.doesNotThrow(
+      () => template1({foo: input.value('static value')}));
+
+    t.doesNotThrow(
+      () => template1({foo: input('outerInput')}));
+
+    t.doesNotThrow(
+      () => template1({foo: input.updateValue()}));
+
+    t.doesNotThrow(
+      () => template1({foo: input.myself()}));
+
+    quickThrows(t, template1,
+      {foo: input.staticValue()},
+      `foo: Expected dependency name or value-providing input() call, got input.staticValue`);
+
+    quickThrows(t, template1,
+      {foo: input.staticDependency()},
+      `foo: Expected dependency name or value-providing input() call, got input.staticDependency`);
+
+    const template2 = templateCompositeFrom({
+      ...stub, inputs: {
+        bar: input.staticDependency(),
+      },
+    });
+
+    t.doesNotThrow(
+      () => template2({bar: 'dependency'}));
+
+    t.doesNotThrow(
+      () => template2({bar: input.dependency('dependency')}));
+
+    quickThrows(t, template2,
+      {bar: input.value(123)},
+      `bar: Expected dependency name, got input.value`);
+
+    quickThrows(t, template2,
+      {bar: input('outOfPlace')},
+      `bar: Expected dependency name, got input`);
+
+    const template3 = templateCompositeFrom({
+      ...stub, inputs: {
+        baz: input.staticValue(),
+      },
+    });
+
+    t.doesNotThrow(
+      () => template3({baz: input.value(1025)}));
+
+    quickThrows(t, template3,
+      {baz: 'dependency'},
+      `baz: Expected input.value() call, got dependency name`);
+
+    quickThrows(t, template3,
+      {baz: input('outOfPlace')},
+      `baz: Expected input.value() call, got input() call`);
+  });
+
+  t.test(`templateCompositeFrom: validate missing / misplaced inputs`, t => {
+    t.plan(1);
+
+    const template = templateCompositeFrom({
+      ...stub, inputs: {
+        foo: input(),
+        bar: input(),
+      },
+    });
+
+    t.throws(
+      () => template({
+        baz: 'aeiou',
+        raz: input.value(123),
+      }),
+      {message: `Errors in input options passed to stubComposite`, errors: [
+        {message: `Unexpected input names: baz, raz`},
+        {message: `Required these inputs: foo, bar`},
+      ]});
+  });
+
+  t.test(`templateCompositeFrom: validate acceptsNull / defaultValue: null`, t => {
+    t.plan(3);
+
+    const template1 = templateCompositeFrom({
+      ...stub, inputs: {
+        foo: input(),
+      },
+    });
+
+    t.throws(
+      () => template1({}),
+      {message: `Errors in input options passed to stubComposite`, errors: [
+        {message: `Required these inputs: foo`},
+      ]},
+      `throws if input missing and not marked specially`);
+
+    const template2 = templateCompositeFrom({
+      ...stub, inputs: {
+        bar: input({acceptsNull: true}),
+      },
+    });
+
+    t.throws(
+      () => template2({}),
+      {message: `Errors in input options passed to stubComposite`, errors: [
+        {message: `Required these inputs: bar`},
+      ]},
+      `throws if input missing even if marked {acceptsNull}`);
+
+    const template3 = templateCompositeFrom({
+      ...stub, inputs: {
+        baz: input({defaultValue: null}),
+      },
+    });
+
+    t.doesNotThrow(
+      () => template3({}),
+      `does not throw if input missing if marked {defaultValue: null}`);
+  });
+});
diff --git a/test/unit/data/things/album.js b/test/unit/data/things/album.js
new file mode 100644
index 00000000..76a2b90f
--- /dev/null
+++ b/test/unit/data/things/album.js
@@ -0,0 +1,411 @@
+import t from 'tap';
+
+import {linkAndBindWikiData} from '#test-lib';
+import thingConstructors from '#things';
+
+const {
+  Album,
+  Artist,
+  Track,
+} = thingConstructors;
+
+function stubArtistAndContribs() {
+  const artist = new Artist();
+  artist.name = `Test Artist`;
+
+  const contribs = [{who: `Test Artist`, what: null}];
+  const badContribs = [{who: `Figment of Your Imagination`, what: null}];
+
+  return {artist, contribs, badContribs};
+}
+
+function stubTrack(directory = 'foo') {
+  const track = new Track();
+  track.directory = directory;
+
+  return track;
+}
+
+t.test(`Album.bannerDimensions`, t => {
+  t.plan(4);
+
+  const album = new Album();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+  });
+
+  t.equal(album.bannerDimensions, null,
+    `Album.bannerDimensions #1: defaults to null`);
+
+  album.bannerDimensions = [1200, 275];
+
+  t.equal(album.bannerDimensions, null,
+    `Album.bannerDimensions #2: is null if bannerArtistContribs empty`);
+
+  album.bannerArtistContribs = badContribs;
+
+  t.equal(album.bannerDimensions, null,
+    `Album.bannerDimensions #3: is null if bannerArtistContribs resolves empty`);
+
+  album.bannerArtistContribs = contribs;
+
+  t.same(album.bannerDimensions, [1200, 275],
+    `Album.bannerDimensions #4: is own value`);
+});
+
+t.test(`Album.bannerFileExtension`, t => {
+  t.plan(5);
+
+  const album = new Album();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+  });
+
+  t.equal(album.bannerFileExtension, null,
+    `Album.bannerFileExtension #1: defaults to null`);
+
+  album.bannerFileExtension = 'png';
+
+  t.equal(album.bannerFileExtension, null,
+    `Album.bannerFileExtension #2: is null if bannerArtistContribs empty`);
+
+  album.bannerArtistContribs = badContribs;
+
+  t.equal(album.bannerFileExtension, null,
+    `Album.bannerFileExtension #3: is null if bannerArtistContribs resolves empty`);
+
+  album.bannerArtistContribs = contribs;
+
+  t.equal(album.bannerFileExtension, 'png',
+    `Album.bannerFileExtension #4: is own value`);
+
+  album.bannerFileExtension = null;
+
+  t.equal(album.bannerFileExtension, 'jpg',
+    `Album.bannerFileExtension #5: defaults to jpg`);
+});
+
+t.test(`Album.bannerStyle`, t => {
+  t.plan(4);
+
+  const album = new Album();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+  });
+
+  t.equal(album.bannerStyle, null,
+    `Album.bannerStyle #1: defaults to null`);
+
+  album.bannerStyle = `opacity: 0.5`;
+
+  t.equal(album.bannerStyle, null,
+    `Album.bannerStyle #2: is null if bannerArtistContribs empty`);
+
+  album.bannerArtistContribs = badContribs;
+
+  t.equal(album.bannerStyle, null,
+    `Album.bannerStyle #3: is null if bannerArtistContribs resolves empty`);
+
+  album.bannerArtistContribs = contribs;
+
+  t.equal(album.bannerStyle, `opacity: 0.5`,
+    `Album.bannerStyle #4: is own value`);
+});
+
+t.test(`Album.coverArtDate`, t => {
+  t.plan(6);
+
+  const album = new Album();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+  });
+
+  t.equal(album.coverArtDate, null,
+    `Album.coverArtDate #1: defaults to null`);
+
+  album.date = new Date('2012-10-25');
+
+  t.equal(album.coverArtDate, null,
+    `Album.coverArtDate #2: is null if coverArtistContribs empty (1/2)`);
+
+  album.coverArtDate = new Date('2011-04-13');
+
+  t.equal(album.coverArtDate, null,
+    `Album.coverArtDate #3: is null if coverArtistContribs empty (2/2)`);
+
+  album.coverArtistContribs = contribs;
+
+  t.same(album.coverArtDate, new Date('2011-04-13'),
+    `Album.coverArtDate #4: is own value`);
+
+  album.coverArtDate = null;
+
+  t.same(album.coverArtDate, new Date(`2012-10-25`),
+    `Album.coverArtDate #5: inherits album release date`);
+
+  album.coverArtistContribs = badContribs;
+
+  t.equal(album.coverArtDate, null,
+    `Album.coverArtDate #6: is null if coverArtistContribs resolves empty`);
+});
+
+t.test(`Album.coverArtFileExtension`, t => {
+  t.plan(5);
+
+  const album = new Album();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+  });
+
+  t.equal(album.coverArtFileExtension, null,
+    `Album.coverArtFileExtension #1: is null if coverArtistContribs empty (1/2)`);
+
+  album.coverArtFileExtension = 'png';
+
+  t.equal(album.coverArtFileExtension, null,
+    `Album.coverArtFileExtension #2: is null if coverArtistContribs empty (2/2)`);
+
+  album.coverArtFileExtension = null;
+  album.coverArtistContribs = contribs;
+
+  t.equal(album.coverArtFileExtension, 'jpg',
+    `Album.coverArtFileExtension #3: defaults to jpg`);
+
+  album.coverArtFileExtension = 'png';
+
+  t.equal(album.coverArtFileExtension, 'png',
+    `Album.coverArtFileExtension #4: is own value`);
+
+  album.coverArtistContribs = badContribs;
+
+  t.equal(album.coverArtFileExtension, null,
+    `Album.coverArtFileExtension #5: is null if coverArtistContribs resolves empty`);
+});
+
+t.test(`Album.tracks`, t => {
+  t.plan(5);
+
+  const album = new Album();
+  const track1 = stubTrack('track1');
+  const track2 = stubTrack('track2');
+  const track3 = stubTrack('track3');
+
+  linkAndBindWikiData({
+    albumData: [album],
+    trackData: [track1, track2, track3],
+  });
+
+  t.same(album.tracks, [],
+    `Album.tracks #1: defaults to empty array`);
+
+  album.trackSections = [
+    {tracks: ['track:track1', 'track:track2', 'track:track3']},
+  ];
+
+  t.same(album.tracks, [track1, track2, track3],
+    `Album.tracks #2: pulls tracks from one track section`);
+
+  album.trackSections = [
+    {tracks: ['track:track1']},
+    {tracks: ['track:track2', 'track:track3']},
+  ];
+
+  t.same(album.tracks, [track1, track2, track3],
+    `Album.tracks #3: pulls tracks from multiple track sections`);
+
+  album.trackSections = [
+    {tracks: ['track:track1', 'track:does-not-exist']},
+    {tracks: ['track:this-one-neither', 'track:track2']},
+    {tracks: ['track:effectively-empty-section']},
+    {tracks: ['track:track3']},
+  ];
+
+  t.same(album.tracks, [track1, track2, track3],
+    `Album.tracks #4: filters out references without matches`);
+
+  album.trackSections = [
+    {tracks: ['track:track1']},
+    {},
+    {tracks: ['track:track2']},
+    {},
+    {},
+    {tracks: ['track:track3']},
+  ];
+
+  t.same(album.tracks, [track1, track2, track3],
+    `Album.tracks #5: skips missing tracks property`);
+});
+
+t.test(`Album.trackSections`, t => {
+  t.plan(7);
+
+  const album = new Album();
+  const track1 = stubTrack('track1');
+  const track2 = stubTrack('track2');
+  const track3 = stubTrack('track3');
+  const track4 = stubTrack('track4');
+
+  linkAndBindWikiData({
+    albumData: [album],
+    trackData: [track1, track2, track3, track4],
+  });
+
+  album.trackSections = [
+    {tracks: ['track:track1', 'track:track2']},
+    {tracks: ['track:track3', 'track:track4']},
+  ];
+
+  t.match(album.trackSections, [
+    {tracks: [track1, track2]},
+    {tracks: [track3, track4]},
+  ], `Album.trackSections #1: exposes tracks`);
+
+  t.match(album.trackSections, [
+    {tracks: [track1, track2], startIndex: 0},
+    {tracks: [track3, track4], startIndex: 2},
+  ], `Album.trackSections #2: exposes startIndex`);
+
+  album.trackSections = [
+    {name: 'First section', tracks: ['track:track1']},
+    {name: 'Second section', tracks: ['track:track2']},
+    {tracks: ['track:track3']},
+  ];
+
+  t.match(album.trackSections, [
+    {name: 'First section', tracks: [track1]},
+    {name: 'Second section', tracks: [track2]},
+    {name: 'Unnamed Track Section', tracks: [track3]},
+  ], `Album.trackSections #3: exposes name, with fallback value`);
+
+  album.color = '#123456';
+
+  album.trackSections = [
+    {tracks: ['track:track1'], color: null},
+    {tracks: ['track:track2'], color: '#abcdef'},
+    {tracks: ['track:track3'], color: null},
+  ];
+
+  t.match(album.trackSections, [
+    {tracks: [track1], color: '#123456'},
+    {tracks: [track2], color: '#abcdef'},
+    {tracks: [track3], color: '#123456'},
+  ], `Album.trackSections #4: exposes color, inherited from album`);
+
+  album.trackSections = [
+    {tracks: ['track:track1'], dateOriginallyReleased: null},
+    {tracks: ['track:track2'], dateOriginallyReleased: new Date('2009-04-11')},
+    {tracks: ['track:track3'], dateOriginallyReleased: null},
+  ];
+
+  t.match(album.trackSections, [
+    {tracks: [track1], dateOriginallyReleased: null},
+    {tracks: [track2], dateOriginallyReleased: new Date('2009-04-11')},
+    {tracks: [track3], dateOriginallyReleased: null},
+  ], `Album.trackSections #5: exposes dateOriginallyReleased, if present`);
+
+  album.trackSections = [
+    {tracks: ['track:track1'], isDefaultTrackSection: true},
+    {tracks: ['track:track2'], isDefaultTrackSection: false},
+    {tracks: ['track:track3'], isDefaultTrackSection: null},
+  ];
+
+  t.match(album.trackSections, [
+    {tracks: [track1], isDefaultTrackSection: true},
+    {tracks: [track2], isDefaultTrackSection: false},
+    {tracks: [track3], isDefaultTrackSection: false},
+  ], `Album.trackSections #6: exposes isDefaultTrackSection, defaults to false`);
+
+  album.trackSections = [
+    {tracks: ['track:track1', 'track:track2', 'track:snooping'], color: '#112233'},
+    {tracks: ['track:track3', 'track:as-usual'],                 color: '#334455'},
+    {tracks: [],                                                 color: '#bbbbba'},
+    {tracks: ['track:icy', 'track:chilly', 'track:frigid'],      color: '#556677'},
+    {tracks: ['track:track4'],                                   color: '#778899'},
+  ];
+
+  t.match(album.trackSections, [
+    {tracks: [track1, track2], color: '#112233'},
+    {tracks: [track3],         color: '#334455'},
+    {tracks: [track4],         color: '#778899'},
+  ], `Album.trackSections #7: filters out references without matches & empty sections`);
+});
+
+t.test(`Album.wallpaperFileExtension`, t => {
+  t.plan(5);
+
+  const album = new Album();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+  });
+
+  t.equal(album.wallpaperFileExtension, null,
+    `Album.wallpaperFileExtension #1: defaults to null`);
+
+  album.wallpaperFileExtension = 'png';
+
+  t.equal(album.wallpaperFileExtension, null,
+    `Album.wallpaperFileExtension #2: is null if wallpaperArtistContribs empty`);
+
+  album.wallpaperArtistContribs = contribs;
+
+  t.equal(album.wallpaperFileExtension, 'png',
+    `Album.wallpaperFileExtension #3: is own value`);
+
+  album.wallpaperFileExtension = null;
+
+  t.equal(album.wallpaperFileExtension, 'jpg',
+    `Album.wallpaperFileExtension #4: defaults to jpg`);
+
+  album.wallpaperArtistContribs = badContribs;
+
+  t.equal(album.wallpaperFileExtension, null,
+    `Album.wallpaperFileExtension #5: is null if wallpaperArtistContribs resolves empty`);
+});
+
+t.test(`Album.wallpaperStyle`, t => {
+  t.plan(4);
+
+  const album = new Album();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+  });
+
+  t.equal(album.wallpaperStyle, null,
+    `Album.wallpaperStyle #1: defaults to null`);
+
+  album.wallpaperStyle = `opacity: 0.5`;
+
+  t.equal(album.wallpaperStyle, null,
+    `Album.wallpaperStyle #2: is null if wallpaperArtistContribs empty`);
+
+  album.wallpaperArtistContribs = badContribs;
+
+  t.equal(album.wallpaperStyle, null,
+    `Album.wallpaperStyle #3: is null if wallpaperArtistContribs resolves empty`);
+
+  album.wallpaperArtistContribs = contribs;
+
+  t.equal(album.wallpaperStyle, `opacity: 0.5`,
+    `Album.wallpaperStyle #4: is own value`);
+});
diff --git a/test/unit/data/things/art-tag.js b/test/unit/data/things/art-tag.js
new file mode 100644
index 00000000..561c93ef
--- /dev/null
+++ b/test/unit/data/things/art-tag.js
@@ -0,0 +1,71 @@
+import t from 'tap';
+
+import {linkAndBindWikiData} from '#test-lib';
+import thingConstructors from '#things';
+
+const {
+  Album,
+  Artist,
+  ArtTag,
+  Track,
+} = thingConstructors;
+
+function stubAlbum(tracks, directory = 'bar') {
+  const album = new Album();
+  album.directory = directory;
+
+  const trackRefs = tracks.map(t => Thing.getReference(t));
+  album.trackSections = [{tracks: trackRefs}];
+
+  return album;
+}
+
+function stubTrack(directory = 'foo') {
+  const track = new Track();
+  track.directory = directory;
+
+  return track;
+}
+
+function stubTrackAndAlbum(trackDirectory = 'foo', albumDirectory = 'bar') {
+  const track = stubTrack(trackDirectory);
+  const album = stubAlbum([track], albumDirectory);
+
+  return {track, album};
+}
+
+function stubArtist(artistName = `Test Artist`) {
+  const artist = new Artist();
+  artist.name = artistName;
+
+  return artist;
+}
+
+function stubArtistAndContribs(artistName = `Test Artist`) {
+  const artist = stubArtist(artistName);
+  const contribs = [{who: artistName, what: null}];
+  const badContribs = [{who: `Figment of Your Imagination`, what: null}];
+
+  return {artist, contribs, badContribs};
+}
+
+t.test(`ArtTag.nameShort`, t => {
+  t.plan(3);
+
+  const artTag = new ArtTag();
+
+  artTag.name = `Dave Strider`;
+
+  t.equal(artTag.nameShort, `Dave Strider`,
+    `ArtTag #1: defaults to name`);
+
+  artTag.name = `Dave Strider (Homestuck)`;
+
+  t.equal(artTag.nameShort, `Dave Strider`,
+    `ArtTag #2: trims parenthical part at end`);
+
+  artTag.name = `This (And) That (Then)`;
+
+  t.equal(artTag.nameShort, `This (And) That`,
+    `ArtTag #2: doesn't trim midlde parenthical part`);
+});
diff --git a/test/unit/data/things/flash.js b/test/unit/data/things/flash.js
new file mode 100644
index 00000000..62059604
--- /dev/null
+++ b/test/unit/data/things/flash.js
@@ -0,0 +1,55 @@
+import t from 'tap';
+
+import {linkAndBindWikiData} from '#test-lib';
+import thingConstructors from '#things';
+
+const {
+  Flash,
+  FlashAct,
+  Thing,
+} = thingConstructors;
+
+function stubFlash(directory = 'foo') {
+  const flash = new Flash();
+  flash.directory = directory;
+
+  return flash;
+}
+
+function stubFlashAct(flashes, directory = 'bar') {
+  const flashAct = new FlashAct();
+  flashAct.directory = directory;
+  flashAct.flashes = flashes.map(flash => Thing.getReference(flash));
+
+  return flashAct;
+}
+
+t.test(`Flash.color`, t => {
+  t.plan(4);
+
+  const flash = stubFlash();
+  const flashAct = stubFlashAct([flash]);
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    flashData: [flash],
+    flashActData: [flashAct],
+  });
+
+  t.equal(flash.color, null,
+    `color #1: defaults to null`);
+
+  flashAct.color = '#abcdef';
+  XXX_decacheWikiData();
+
+  t.equal(flash.color, '#abcdef',
+    `color #2: inherits from flash act`);
+
+  flash.color = '#123456';
+
+  t.equal(flash.color, '#123456',
+    `color #3: is own value`);
+
+  t.throws(() => { flash.color = '#aeiouw'; },
+    {cause: TypeError},
+    `color #4: must be set to valid color`);
+});
diff --git a/test/unit/data/things/track.js b/test/unit/data/things/track.js
index 383e3e3f..806efbf1 100644
--- a/test/unit/data/things/track.js
+++ b/test/unit/data/things/track.js
@@ -1,74 +1,683 @@
 import t from 'tap';
+
+import {showAggregate} from '#sugar';
+import {linkAndBindWikiData} from '#test-lib';
 import thingConstructors from '#things';
 
 const {
   Album,
+  Artist,
+  Flash,
+  FlashAct,
   Thing,
   Track,
-  TrackGroup,
 } = thingConstructors;
 
-function stubAlbum(tracks) {
+function stubAlbum(tracks, directory = 'bar') {
   const album = new Album();
-  album.trackSections = [
-    {
-      tracksByRef: tracks.map(t => Thing.getReference(t)),
-    },
-  ];
-  album.trackData = tracks;
+  album.directory = directory;
+
+  const trackRefs = tracks.map(t => Thing.getReference(t));
+  album.trackSections = [{tracks: trackRefs}];
+
   return album;
 }
 
-t.test(`Track.coverArtDate`, t => {
+function stubTrack(directory = 'foo') {
+  const track = new Track();
+  track.directory = directory;
+
+  return track;
+}
+
+function stubTrackAndAlbum(trackDirectory = 'foo', albumDirectory = 'bar') {
+  const track = stubTrack(trackDirectory);
+  const album = stubAlbum([track], albumDirectory);
+
+  return {track, album};
+}
+
+function stubArtist(artistName = `Test Artist`) {
+  const artist = new Artist();
+  artist.name = artistName;
+
+  return artist;
+}
+
+function stubArtistAndContribs(artistName = `Test Artist`) {
+  const artist = stubArtist(artistName);
+  const contribs = [{who: artistName, what: null}];
+  const badContribs = [{who: `Figment of Your Imagination`, what: null}];
+
+  return {artist, contribs, badContribs};
+}
+
+function stubFlashAndAct(directory = 'zam') {
+  const flash = new Flash();
+  flash.directory = directory;
+
+  const flashAct = new FlashAct();
+  flashAct.flashes = [Thing.getReference(flash)];
+
+  return {flash, flashAct};
+}
+
+t.test(`Track.album`, t => {
+  t.plan(6);
+
+  // Note: These asserts use manual albumData/trackData relationships
+  // to illustrate more specifically the properties which are expected to
+  // be relevant for this case. Other properties use the same underlying
+  // get-album behavior as Track.album so aren't tested as aggressively.
+
+  const track1 = stubTrack('track1');
+  const track2 = stubTrack('track2');
+  const album1 = new Album();
+  const album2 = new Album();
+
+  t.equal(track1.album, null,
+    `album #1: defaults to null`);
+
+  track1.albumData = [album1, album2];
+  track2.albumData = [album1, album2];
+  album1.trackData = [track1, track2];
+  album2.trackData = [track1, track2];
+  album1.trackSections = [{tracks: ['track:track1']}];
+  album2.trackSections = [{tracks: ['track:track2']}];
+
+  t.equal(track1.album, album1,
+    `album #2: is album when album's trackSections matches track`);
+
+  track1.albumData = [album2, album1];
+
+  t.equal(track1.album, album1,
+    `album #3: is album when albumData is in different order`);
+
+  track1.albumData = [];
+
+  t.equal(track1.album, null,
+    `album #4: is null when track missing albumData`);
+
+  album1.trackData = [];
+  track1.albumData = [album1, album2];
+
+  t.equal(track1.album, null,
+    `album #5: is null when album missing trackData`);
+
+  album1.trackData = [track1, track2];
+  album1.trackSections = [{tracks: ['track:track2']}];
+
+  // XXX_decacheWikiData
+  track1.albumData = [];
+  track1.albumData = [album1, album2];
+
+  t.equal(track1.album, null,
+    `album #6: is null when album's trackSections don't match track`);
+});
+
+t.test(`Track.artistContribs`, t => {
+  t.plan(4);
+
+  const {track, album} = stubTrackAndAlbum();
+  const artist1 = stubArtist(`Artist 1`);
+  const artist2 = stubArtist(`Artist 2`);
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist1, artist2],
+    trackData: [track],
+  });
+
+  t.same(track.artistContribs, [],
+    `artistContribs #1: defaults to empty array`);
+
+  album.artistContribs = [
+    {who: `Artist 1`, what: `composition`},
+    {who: `Artist 2`, what: null},
+  ];
+
+  XXX_decacheWikiData();
+
+  t.same(track.artistContribs,
+    [{who: artist1, what: `composition`}, {who: artist2, what: null}],
+    `artistContribs #2: inherits album artistContribs`);
+
+  track.artistContribs = [
+    {who: `Artist 1`, what: `arrangement`},
+  ];
+
+  t.same(track.artistContribs, [{who: artist1, what: `arrangement`}],
+    `artistContribs #3: resolves from own value`);
+
+  track.artistContribs = [
+    {who: `Artist 1`, what: `snooping`},
+    {who: `Artist 413`, what: `as`},
+    {who: `Artist 2`, what: `usual`},
+  ];
+
+  t.same(track.artistContribs,
+    [{who: artist1, what: `snooping`}, {who: artist2, what: `usual`}],
+    `artistContribs #4: filters out names without matches`);
+});
+
+t.test(`Track.color`, t => {
   t.plan(5);
 
-  // Priority order is as follows, with the last (trackCoverArtDate) being
-  // greatest priority.
-  const albumDate = new Date('2010-10-10');
-  const albumTrackArtDate = new Date('2012-12-12');
-  const trackDateFirstReleased = new Date('2008-08-08');
-  const trackCoverArtDate = new Date('2009-09-09');
+  const {track, album} = stubTrackAndAlbum();
+
+  const {wikiData, linkWikiDataArrays, XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album],
+    trackData: [track],
+  });
+
+  t.equal(track.color, null,
+    `color #1: defaults to null`);
+
+  album.color = '#abcdef';
+  album.trackSections = [{
+    color: '#beeeef',
+    tracks: [Thing.getReference(track)],
+  }];
+  XXX_decacheWikiData();
+
+  t.equal(track.color, '#beeeef',
+    `color #2: inherits from track section before album`);
+
+  // Replace the album with a completely fake one. This isn't realistic, since
+  // in correct data, Album.tracks depends on Albums.trackSections and so the
+  // track's album will always have a corresponding track section. But if that
+  // connection breaks for some future reason (with the album still present),
+  // Track.color should still inherit directly from the album.
+  wikiData.albumData = [
+    new Proxy({
+      color: '#abcdef',
+      tracks: [track],
+      trackSections: [
+        {color: '#baaaad', tracks: []},
+      ],
+    }, {getPrototypeOf: () => Album.prototype}),
+  ];
+
+  linkWikiDataArrays();
+
+  t.equal(track.color, '#abcdef',
+    `color #3: inherits from album without matching track section`);
+
+  track.color = '#123456';
+
+  t.equal(track.color, '#123456',
+    `color #4: is own value`);
+
+  t.throws(() => { track.color = '#aeiouw'; },
+    {cause: TypeError},
+    `color #5: must be set to valid color`);
+});
+
+t.test(`Track.commentatorArtists`, t => {
+  t.plan(6);
 
   const track = new Track();
-  track.directory = 'foo';
+  const artist1 = stubArtist(`SnooPING`);
+  const artist2 = stubArtist(`ASUsual`);
+  const artist3 = stubArtist(`Icy`);
+
+  linkAndBindWikiData({
+    trackData: [track],
+    artistData: [artist1, artist2, artist3],
+  });
+
+  track.commentary =
+    `<i>SnooPING:</i>\n` +
+    `Wow.\n`;
+
+  t.same(track.commentatorArtists, [artist1],
+    `Track.commentatorArtists #1: works with one commentator`);
+
+  track.commentary +=
+    `<i>ASUsual:</i>\n` +
+    `Yes!\n`;
+
+  t.same(track.commentatorArtists, [artist1, artist2],
+    `Track.commentatorArtists #2: works with two commentators`);
+
+  track.commentary +=
+    `<i><b>Icy:</b></i>\n` +
+    `Incredible.\n`;
+
+  t.same(track.commentatorArtists, [artist1, artist2, artist3],
+    `Track.commentatorArtists #3: works with boldface name`);
+
+  track.commentary =
+    `<i>Icy:</i> (project manager)\n` +
+    `Very good track.\n`;
+
+  t.same(track.commentatorArtists, [artist3],
+    `Track.commentatorArtists #4: works with parenthical accent`);
+
+  track.commentary +=
+    `<i>SNooPING ASUsual Icy:</i>\n` +
+    `WITH ALL THREE POWERS COMBINED...`;
+
+  t.same(track.commentatorArtists, [artist3],
+    `Track.commentatorArtists #5: ignores artist names not found`);
+
+  track.commentary +=
+    `<i>Icy:</i>\n` +
+    `I'm back!\n`;
+
+  t.same(track.commentatorArtists, [artist3],
+    `Track.commentatorArtists #6: ignores duplicate artist`);
+});
+
+t.test(`Track.coverArtistContribs`, t => {
+  t.plan(5);
+
+  const {track, album} = stubTrackAndAlbum();
+  const artist1 = stubArtist(`Artist 1`);
+  const artist2 = stubArtist(`Artist 2`);
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist1, artist2],
+    trackData: [track],
+  });
+
+  t.same(track.coverArtistContribs, [],
+    `coverArtistContribs #1: defaults to empty array`);
+
+  album.trackCoverArtistContribs = [
+    {who: `Artist 1`, what: `lines`},
+    {who: `Artist 2`, what: null},
+  ];
+
+  XXX_decacheWikiData();
+
+  t.same(track.coverArtistContribs,
+    [{who: artist1, what: `lines`}, {who: artist2, what: null}],
+    `coverArtistContribs #2: inherits album trackCoverArtistContribs`);
+
+  track.coverArtistContribs = [
+    {who: `Artist 1`, what: `collage`},
+  ];
+
+  t.same(track.coverArtistContribs, [{who: artist1, what: `collage`}],
+    `coverArtistContribs #3: resolves from own value`);
+
+  track.coverArtistContribs = [
+    {who: `Artist 1`, what: `snooping`},
+    {who: `Artist 413`, what: `as`},
+    {who: `Artist 2`, what: `usual`},
+  ];
+
+  t.same(track.coverArtistContribs,
+    [{who: artist1, what: `snooping`}, {who: artist2, what: `usual`}],
+    `coverArtistContribs #4: filters out names without matches`);
+
+  track.disableUniqueCoverArt = true;
+
+  t.same(track.coverArtistContribs, [],
+    `coverArtistContribs #5: is empty if track disables unique cover artwork`);
+});
+
+t.test(`Track.coverArtDate`, t => {
+  t.plan(8);
+
+  const {track, album} = stubTrackAndAlbum();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+    trackData: [track],
+  });
+
+  track.coverArtistContribs = contribs;
 
-  const album = stubAlbum([track]);
+  t.equal(track.coverArtDate, null,
+    `coverArtDate #1: defaults to null`);
 
-  track.albumData = [album];
+  album.trackArtDate = new Date('2012-12-12');
 
-  // 1. coverArtDate defaults to null
+  XXX_decacheWikiData();
 
-  t.equal(track.coverArtDate, null);
+  t.same(track.coverArtDate, new Date('2012-12-12'),
+    `coverArtDate #2: inherits album trackArtDate`);
 
-  // 2. coverArtDate inherits album release date
+  track.coverArtDate = new Date('2009-09-09');
 
-  album.date = albumDate;
+  t.same(track.coverArtDate, new Date('2009-09-09'),
+    `coverArtDate #3: is own value`);
 
-  // XXX clear cache so change in album's property is reflected
-  track.albumData = [];
-  track.albumData = [album];
+  track.coverArtistContribs = [];
 
-  t.equal(track.coverArtDate, albumDate);
+  t.equal(track.coverArtDate, null,
+    `coverArtDate #4: is null if track coverArtistContribs empty`);
+
+  album.trackCoverArtistContribs = contribs;
+
+  XXX_decacheWikiData();
+
+  t.same(track.coverArtDate, new Date('2009-09-09'),
+    `coverArtDate #5: is not null if album trackCoverArtistContribs specified`);
+
+  album.trackCoverArtistContribs = badContribs;
+
+  XXX_decacheWikiData();
+
+  t.equal(track.coverArtDate, null,
+    `coverArtDate #6: is null if album trackCoverArtistContribs resolves empty`);
+
+  track.coverArtistContribs = badContribs;
+
+  t.equal(track.coverArtDate, null,
+    `coverArtDate #7: is null if track coverArtistContribs resolves empty`);
+
+  track.coverArtistContribs = contribs;
+  track.disableUniqueCoverArt = true;
+
+  t.equal(track.coverArtDate, null,
+    `coverArtDate #8: is null if track disables unique cover artwork`);
+});
+
+t.test(`Track.coverArtFileExtension`, t => {
+  t.plan(8);
+
+  const {track, album} = stubTrackAndAlbum();
+  const {artist, contribs} = stubArtistAndContribs();
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+    trackData: [track],
+  });
+
+  t.equal(track.coverArtFileExtension, null,
+    `coverArtFileExtension #1: defaults to null`);
+
+  track.coverArtistContribs = contribs;
+
+  t.equal(track.coverArtFileExtension, 'jpg',
+    `coverArtFileExtension #2: is jpg if has cover art and not further specified`);
+
+  track.coverArtistContribs = [];
+
+  album.coverArtistContribs = contribs;
+  XXX_decacheWikiData();
+
+  t.equal(track.coverArtFileExtension, null,
+    `coverArtFileExtension #3: only has value for unique cover art`);
+
+  track.coverArtistContribs = contribs;
+
+  album.trackCoverArtFileExtension = 'png';
+  XXX_decacheWikiData();
+
+  t.equal(track.coverArtFileExtension, 'png',
+    `coverArtFileExtension #4: inherits album trackCoverArtFileExtension (1/2)`);
+
+  track.coverArtFileExtension = 'gif';
+
+  t.equal(track.coverArtFileExtension, 'gif',
+    `coverArtFileExtension #5: is own value (1/2)`);
+
+  track.coverArtistContribs = [];
+
+  album.trackCoverArtistContribs = contribs;
+  XXX_decacheWikiData();
+
+  t.equal(track.coverArtFileExtension, 'gif',
+    `coverArtFileExtension #6: is own value (2/2)`);
+
+  track.coverArtFileExtension = null;
+
+  t.equal(track.coverArtFileExtension, 'png',
+    `coverArtFileExtension #7: inherits album trackCoverArtFileExtension (2/2)`);
+
+  track.disableUniqueCoverArt = true;
+
+  t.equal(track.coverArtFileExtension, null,
+    `coverArtFileExtension #8: is null if track disables unique cover art`);
+});
+
+t.test(`Track.date`, t => {
+  t.plan(3);
+
+  const {track, album} = stubTrackAndAlbum();
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album],
+    trackData: [track],
+  });
+
+  t.equal(track.date, null,
+    `date #1: defaults to null`);
+
+  album.date = new Date('2012-12-12');
+  XXX_decacheWikiData();
+
+  t.same(track.date, album.date,
+    `date #2: inherits from album`);
+
+  track.dateFirstReleased = new Date('2009-09-09');
+
+  t.same(track.date, new Date('2009-09-09'),
+    `date #3: is own dateFirstReleased`);
+});
+
+t.test(`Track.featuredInFlashes`, t => {
+  t.plan(2);
+
+  const {track, album} = stubTrackAndAlbum('track1');
+
+  const {flash: flash1, flashAct: flashAct1} = stubFlashAndAct('flash1');
+  const {flash: flash2, flashAct: flashAct2} = stubFlashAndAct('flash2');
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album],
+    trackData: [track],
+    flashData: [flash1, flash2],
+    flashActData: [flashAct1, flashAct2],
+  });
+
+  t.same(track.featuredInFlashes, [],
+    `featuredInFlashes #1: defaults to empty array`);
+
+  flash1.featuredTracks = ['track:track1'];
+  flash2.featuredTracks = ['track:track1'];
+  XXX_decacheWikiData();
+
+  t.same(track.featuredInFlashes, [flash1, flash2],
+    `featuredInFlashes #2: matches flashes' featuredTracks`);
+});
+
+t.test(`Track.hasUniqueCoverArt`, t => {
+  t.plan(7);
+
+  const {track, album} = stubTrackAndAlbum();
+  const {artist, contribs, badContribs} = stubArtistAndContribs();
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album],
+    artistData: [artist],
+    trackData: [track],
+  });
+
+  t.equal(track.hasUniqueCoverArt, false,
+    `hasUniqueCoverArt #1: defaults to false`);
+
+  album.trackCoverArtistContribs = contribs;
+  XXX_decacheWikiData();
+
+  t.equal(track.hasUniqueCoverArt, true,
+    `hasUniqueCoverArt #2: is true if album specifies trackCoverArtistContribs`);
+
+  track.disableUniqueCoverArt = true;
+
+  t.equal(track.hasUniqueCoverArt, false,
+    `hasUniqueCoverArt #3: is false if disableUniqueCoverArt is true (1/2)`);
+
+  track.disableUniqueCoverArt = false;
+
+  album.trackCoverArtistContribs = badContribs;
+  XXX_decacheWikiData();
+
+  t.equal(track.hasUniqueCoverArt, false,
+    `hasUniqueCoverArt #4: is false if album's trackCoverArtistContribs resolve empty`);
+
+  track.coverArtistContribs = contribs;
+
+  t.equal(track.hasUniqueCoverArt, true,
+    `hasUniqueCoverArt #5: is true if track specifies coverArtistContribs`);
+
+  track.disableUniqueCoverArt = true;
+
+  t.equal(track.hasUniqueCoverArt, false,
+    `hasUniqueCoverArt #6: is false if disableUniqueCoverArt is true (2/2)`);
+
+  track.disableUniqueCoverArt = false;
+
+  track.coverArtistContribs = badContribs;
+
+  t.equal(track.hasUniqueCoverArt, false,
+    `hasUniqueCoverArt #7: is false if track's coverArtistContribs resolve empty`);
+});
+
+t.test(`Track.originalReleaseTrack`, t => {
+  t.plan(3);
+
+  const {track: track1, album: album1} = stubTrackAndAlbum('track1');
+  const {track: track2, album: album2} = stubTrackAndAlbum('track2');
+
+  const {wikiData, linkWikiDataArrays, XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album1, album2],
+    trackData: [track1, track2],
+  });
+
+  t.equal(track2.originalReleaseTrack, null,
+    `originalReleaseTrack #1: defaults to null`);
+
+  track2.originalReleaseTrack = 'track:track1';
+
+  t.equal(track2.originalReleaseTrack, track1,
+    `originalReleaseTrack #2: is resolved from own value`);
+
+  track2.trackData = [];
+
+  t.equal(track2.originalReleaseTrack, null,
+    `originalReleaseTrack #3: is null when track missing trackData`);
+});
+
+t.test(`Track.otherReleases`, t => {
+  t.plan(6);
+
+  const {track: track1, album: album1} = stubTrackAndAlbum('track1');
+  const {track: track2, album: album2} = stubTrackAndAlbum('track2');
+  const {track: track3, album: album3} = stubTrackAndAlbum('track3');
+  const {track: track4, album: album4} = stubTrackAndAlbum('track4');
+
+  const {wikiData, linkWikiDataArrays, XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album1, album2, album3, album4],
+    trackData: [track1, track2, track3, track4],
+  });
+
+  t.same(track1.otherReleases, [],
+    `otherReleases #1: defaults to empty array`);
+
+  track2.originalReleaseTrack = 'track:track1';
+  track3.originalReleaseTrack = 'track:track1';
+  track4.originalReleaseTrack = 'track:track1';
+  XXX_decacheWikiData();
+
+  t.same(track1.otherReleases, [track2, track3, track4],
+    `otherReleases #2: otherReleases of original release are its rereleases`);
+
+  wikiData.trackData = [track1, track3, track2, track4];
+  linkWikiDataArrays();
+
+  t.same(track1.otherReleases, [track3, track2, track4],
+    `otherReleases #3: otherReleases matches trackData order`);
+
+  wikiData.trackData = [track3, track2, track1, track4];
+  linkWikiDataArrays();
+
+  t.same(track2.otherReleases, [track1, track3, track4],
+    `otherReleases #4: otherReleases of rerelease are original track then other rereleases (1/3)`);
+
+  t.same(track3.otherReleases, [track1, track2, track4],
+    `otherReleases #5: otherReleases of rerelease are original track then other rereleases (2/3)`);
+
+  t.same(track4.otherReleases, [track1, track3, track2],
+    `otherReleases #6: otherReleases of rerelease are original track then other rereleases (3/3)`);
+});
+
+t.test(`Track.referencedByTracks`, t => {
+  t.plan(4);
+
+  const {track: track1, album: album1} = stubTrackAndAlbum('track1');
+  const {track: track2, album: album2} = stubTrackAndAlbum('track2');
+  const {track: track3, album: album3} = stubTrackAndAlbum('track3');
+  const {track: track4, album: album4} = stubTrackAndAlbum('track4');
+
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album1, album2, album3, album4],
+    trackData: [track1, track2, track3, track4],
+  });
+
+  t.same(track1.referencedByTracks, [],
+    `referencedByTracks #1: defaults to empty array`);
+
+  track2.referencedTracks = ['track:track1'];
+  track3.referencedTracks = ['track:track1'];
+  XXX_decacheWikiData();
+
+  t.same(track1.referencedByTracks, [track2, track3],
+    `referencedByTracks #2: matches tracks' referencedTracks`);
+
+  track4.sampledTracks = ['track:track1'];
+  XXX_decacheWikiData();
+
+  t.same(track1.referencedByTracks, [track2, track3],
+    `referencedByTracks #3: doesn't match tracks' sampledTracks`);
+
+  track3.originalReleaseTrack = 'track:track2';
+  XXX_decacheWikiData();
+
+  t.same(track1.referencedByTracks, [track2],
+    `referencedByTracks #4: doesn't include re-releases`);
+});
 
-  // 3. coverArtDate inherits album trackArtDate
+t.test(`Track.sampledByTracks`, t => {
+  t.plan(4);
 
-  album.trackArtDate = albumTrackArtDate;
+  const {track: track1, album: album1} = stubTrackAndAlbum('track1');
+  const {track: track2, album: album2} = stubTrackAndAlbum('track2');
+  const {track: track3, album: album3} = stubTrackAndAlbum('track3');
+  const {track: track4, album: album4} = stubTrackAndAlbum('track4');
 
-  // XXX clear cache again
-  track.albumData = [];
-  track.albumData = [album];
+  const {XXX_decacheWikiData} = linkAndBindWikiData({
+    albumData: [album1, album2, album3, album4],
+    trackData: [track1, track2, track3, track4],
+  });
 
-  t.equal(track.coverArtDate, albumTrackArtDate);
+  t.same(track1.sampledByTracks, [],
+    `sampledByTracks #1: defaults to empty array`);
 
-  // 4. coverArtDate is overridden dateFirstReleased
+  track2.sampledTracks = ['track:track1'];
+  track3.sampledTracks = ['track:track1'];
+  XXX_decacheWikiData();
 
-  track.dateFirstReleased = trackDateFirstReleased;
+  t.same(track1.sampledByTracks, [track2, track3],
+    `sampledByTracks #2: matches tracks' sampledTracks`);
 
-  t.equal(track.coverArtDate, trackDateFirstReleased);
+  track4.referencedTracks = ['track:track1'];
+  XXX_decacheWikiData();
 
-  // 5. coverArtDate is overridden coverArtDate
+  t.same(track1.sampledByTracks, [track2, track3],
+    `sampledByTracks #3: doesn't match tracks' referencedTracks`);
 
-  track.coverArtDate = trackCoverArtDate;
+  track3.originalReleaseTrack = 'track:track2';
+  XXX_decacheWikiData();
 
-  t.equal(track.coverArtDate, trackCoverArtDate);
+  t.same(track1.sampledByTracks, [track2],
+    `sampledByTracks #4: doesn't include re-releases`);
 });