Core: Add automatic labels in test.each() for primitive values in arrays

Fixes #1733.

docs/api/QUnit/test.each.md

@@ -38,6 +38,11 @@ Each test case is passed one value of your dataset.
 
 The [`only`](./test.only.md), [`todo`](./test.todo.md), [`skip`](./test.skip.md), and [`if`](./test.if.md) variants are also available, as `QUnit.test.only.each`, `QUnit.test.todo.each`, `QUnit.test.skip.each`, and `QUnit.test.if.each` respectively.
 
+## Changelog
+
+| UNRELEASED | Add [automatic labels](https://github.com/qunitjs/qunit/issues/1733) for primitive values in arrays.
+| [QUnit 2.16.0](https://github.com/qunitjs/qunit/releases/tag/2.16.0) | Introduce `QUnit.test.each()`.
+
 ## Examples
 
 ### Basic data provider
@@ -50,6 +55,14 @@ function isEven (x) {
 QUnit.test.each('isEven()', [2, 4, 6], (assert, data) => {
   assert.true(isEven(data), `${data} is even`);
 });
+
+QUnit.test.each('truthy', ['a', 42, true, Infinity], (assert, data) => {
+  assert.true(!!data);
+});
+
+QUnit.test.each('falsy', [false, null], (assert, data) => {
+  assert.false(!!data);
+});
 ```
 
 ### Array data provider

src/core/test.js

@@ -932,7 +932,19 @@ function makeEachTestName (testName, argument) {
 function runEach (data, eachFn) {
   if (Array.isArray(data)) {
     for (let i = 0; i < data.length; i++) {
-      eachFn(data[i], i);
+      const value = data[i];
+      const valueType = typeof value;
+      let testKey;
+      if (valueType === 'string' || valueType === 'number' || valueType === 'boolean' || valueType === 'undefined' || value === null) {
+        const valueForName = String(value);
+        testKey = i + ': ' + (valueForName.length <= 30
+          ? valueForName
+          : valueForName.slice(0, 29) + '…'
+        );
+      } else {
+        testKey = i;
+      }
+      eachFn(value, testKey);
     }
   } else if (typeof data === 'object' && data !== null) {
     for (let key in data) {

test/cli/fixtures/each-array-labels.js

@@ -0,0 +1,44 @@
+// Automatic labels for test.each() array data where possible
+// https://github.com/qunitjs/qunit/issues/1733
+
+QUnit.test.each('array of arrays', [[1, 2, 3], [1, 1, 2]], function (assert, data) {
+  assert.true(true);
+});
+
+QUnit.test.each('array of strings', [
+  'foo',
+  'bar',
+  '',
+  ' ',
+  '_',
+  '+',
+  '^',
+  '$',
+  'x'.repeat(30),
+  'y'.repeat(100)
+], function (assert, data) {
+  assert.true(true);
+});
+
+QUnit.test.each('array of mixed', [
+  undefined,
+  null,
+  false,
+  true,
+  0,
+  1,
+  -10,
+  10/3,
+  10e42,
+  Infinity,
+  NaN,
+  [],
+  {},
+  'some'
+], function (assert, value) {
+  assert.true(true);
+});
+
+QUnit.test.each('keyed objects', { caseFoo: [1, 2, 3], caseBar: [1, 1, 2] }, function (assert, data) {
+  assert.true(true);
+});

test/cli/fixtures/each-array-labels.tap.txt

@@ -0,0 +1,36 @@
+# command: ["qunit", "each-array-labels.js"]
+
+TAP version 13
+ok 1 array of arrays [0]
+ok 2 array of arrays [1]
+ok 3 array of strings [0: foo]
+ok 4 array of strings [1: bar]
+ok 5 array of strings [2: ]
+ok 6 array of strings [3:  ]
+ok 7 array of strings [4: _]
+ok 8 array of strings [5: +]
+ok 9 array of strings [6: ^]
+ok 10 array of strings [7: $]
+ok 11 array of strings [8: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx]
+ok 12 array of strings [9: yyyyyyyyyyyyyyyyyyyyyyyyyyyyy…]
+ok 13 array of mixed [0: undefined]
+ok 14 array of mixed [1: null]
+ok 15 array of mixed [2: false]
+ok 16 array of mixed [3: true]
+ok 17 array of mixed [4: 0]
+ok 18 array of mixed [5: 1]
+ok 19 array of mixed [6: -10]
+ok 20 array of mixed [7: 3.3333333333333335]
+ok 21 array of mixed [8: 1e+43]
+ok 22 array of mixed [9: Infinity]
+ok 23 array of mixed [10: NaN]
+ok 24 array of mixed [11]
+ok 25 array of mixed [12]
+ok 26 array of mixed [13: some]
+ok 27 keyed objects [caseFoo]
+ok 28 keyed objects [caseBar]
+1..28
+# pass 28
+# skip 0
+# todo 0
+# fail 0

test/cli/fixtures/test-if.tap.txt

@@ -5,10 +5,10 @@ TAP version 13
 ok 1 # SKIP skip me
 ok 2 keep me
 ok 3 regular
-ok 4 # SKIP skip dataset [0]
-ok 5 # SKIP skip dataset [1]
-ok 6 keep dataset [0]
-ok 7 keep dataset [1]
+ok 4 # SKIP skip dataset [0: a]
+ok 5 # SKIP skip dataset [1: b]
+ok 6 keep dataset [0: a]
+ok 7 keep dataset [1: b]
 ok 8 # SKIP skip group > skipper
 ok 9 keep group > keeper
 1..9