Jest 的 `it.each()` 描述用于在引用 $predicate 时呈现箭头函数源代码

Question

问题定义

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Jest 允许通过it.each前缀变量在测试用例的数据中使用。name$

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下面的代码产生如下输出：

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 PASS  src/array-functions/find-pairwise.spec.ts\n  findPairwise\n    \xe2\x88\x9a should return [1, 2] for [1, 2, 3] and [Function anonymous] (7ms)\n    \xe2\x88\x9a should return [1, 2] for [1, 2, 3] and [Function anonymous] (1ms)\n    \xe2\x88\x9a should return [2, 3] for [1, 2, 3] and [Function anonymous]\n    \xe2\x88\x9a should return [2, 3] for [1, 2, 3] and [Function anonymous] (1ms)\n    \xe2\x88\x9a should return [undefined, undefined] for [1, 2, 3] and [Function anonymous]\n\nTest Suites: 1 passed, 1 total\nTests:       5 passed, 5 total\nSnapshots:   0 total\nTime:        4.061s\nRan all test suites related to changed files.\n

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正如您所看到的，$expected和$array变量以人类友好的形式呈现（在本例中是基本的 JavaScript 数组）。\n但是，显示的是$predicate通用文本[Function anonymous]而不是实际代码。\n我知道常规函数和如果你调用 JS 中的箭头函数，它们会暴露它们的源代码.toString()。\n有没有办法指示 Jest 渲染该toString()调用的结果？\n我确实尝试过$predicate.toString()，$(predicate.toString())但它们都不起作用。

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代码

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 PASS  src/array-functions/find-pairwise.spec.ts\n  findPairwise\n    \xe2\x88\x9a should return [1, 2] for [1, 2, 3] and [Function anonymous] (7ms)\n    \xe2\x88\x9a should return [1, 2] for [1, 2, 3] and [Function anonymous] (1ms)\n    \xe2\x88\x9a should return [2, 3] for [1, 2, 3] and [Function anonymous]\n    \xe2\x88\x9a should return [2, 3] for [1, 2, 3] and [Function anonymous] (1ms)\n    \xe2\x88\x9a should return [undefined, undefined] for [1, 2, 3] and [Function anonymous]\n\nTest Suites: 1 passed, 1 total\nTests:       5 passed, 5 total\nSnapshots:   0 total\nTime:        4.061s\nRan all test suites related to changed files.\n

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Answer 1

当您使用 的参数的标记模板文字版本时，jest正在幕后使用漂亮格式库从测试数据生成标题（如果测试数据不是原始类型）。tableit.each

不幸的是，出于您的目的，该pretty-format库似乎没有使用toString函数中的方法来格式化它们。

作为替代解决方案，您可以使用参数的数组版本table：

it.each([
    [ [1, 2], [1, 2, 3], (l, r) => l === 1 ],
    [ [1, 2], [1, 2, 3], (l, r) => r === 2 ],
    [ [2, 3], [1, 2, 3], (l, r) => r === 3 ],
    [ [2, 3], [1, 2, 3], (l, r) => l + r === 5 ],
    [ [undefined, undefined], [1, 2, 3], (l, r) => l === r ],
])
('should return %p for %p and %s', (expected, array, predicate) => {
    expect(findPairwise(array, predicate)).toEqual(expected);
});

请注意，我更改了参数的顺序，以便预期值位于第一位。这是因为测试数据和标题中的占位符之间的映射基于tablefor数组版本中的顺序it.each。