开玩笑：对传递给对象的函数的测试失败并显示“已接收：序列化为相同的字符串”

Question

我有一个函数，它接收一个对象数组并返回一个新的对象数组，简化如下：

const injectArray = (arr, fn) => {
  arr.map((el) => ({
    ...el,
    fn: () => fn(el),
  }));
};

对此的测试如下所示：

const mockFn = jest.fn();

describe('injectArray()', () => {
  it('returns a new array with the function injected into the objects', () => {
    expect(injectArray([{
      name: 'John Doe',
      age: 25
    }], mockFn)).toEqual([{
      name: 'John Doe',
      age: 25,
      fn: () => mockFn();
    }]);
  });
});

测试失败

Expected: [{"name": "John Doe", age: 25, "fn": [Function mockFn]}]
Received: serializes to the same string

当我将测试更改为 toContainEqual() 我得到

Expected value: [{"name": "John Doe", age: 25, "fn": [Function mockFn]}]
Received array: [{"name": "John Doe", age: 25, "fn": [Function mockFn]}] 

我相信 Jest 无法比较序列化函数，因此会失败，但在这个特定用例中，我需要将函数传递给对象，如何避免这种情况？

Answer 1

你是对的，jestjs 无法比较序列化的函数。你可以使用expect.any(constructor)。

例如

index.ts:

const injectArray = (arr, fn) => {
  return arr.map((el) => ({
    ...el,
    fn: () => fn(el),
  }));
};

export {injectArray}

index.test.ts:

import {injectArray} from './'

const mockFn = jest.fn();

describe('injectArray()', () => {
  it('returns a new array with the function injected into the objects', () => {
    expect(injectArray([{
      name: 'John Doe',
      age: 25
    }], mockFn)).toEqual([{
      name: 'John Doe',
      age: 25,
      fn: expect.any(Function)
    }]);
  });
});

带有覆盖率报告的单元测试结果：

 PASS  src/stackoverflow/63957885/index.test.ts
  injectArray()
    ✓ returns a new array with the function injected into the objects (4ms)

----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |       80 |      100 |    66.67 |       75 |                   |
 index.ts |       80 |      100 |    66.67 |       75 |                 4 |
----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        5.249s, estimated 13s