Jest.js:在 Jest 中返回为 {} 的布尔返回值

Question

我在下面的返回之前记录了 false 的期望值，这让我感到困惑，因为我不知道{}来自哪里。有人知道原因吗？

FAIL  functions/src/classes/__tests__/ScriptTag.test.ts
constructor
✕ exists() returns false for no matching scriptTag from fake fetch (13ms)
● constructor › exists() returns false for no matching scriptTag from fake fetch
expect(received).toStrictEqual(expected) // deep equality
Expected: false
Received: {}
168 |     const scriptTagTester = new ScriptTagTester("","", "https://firebaseDomain.com/scriptTag.js");
169 | 
> 170 |     await expect(scriptTagTester.exists()).toStrictEqual(false);
|                                            ^
171 | 
172 |   })
173 |   
console.log functions/src/classes/ScriptTag.ts:79
[ 'somescript.js', 'somescript2.js', 'somescript3.js', 'scriptTag.js' ] =====scriptTagFileNames=====
console.log functions/src/classes/ScriptTag.ts:81
true =====found===== // this is for a prior test and probably unrelated
console.log functions/src/classes/ScriptTag.ts:79
[ 'somescript.js', 'somescript2.js' ] =====scriptTagFileNames=====
console.log functions/src/classes/ScriptTag.ts:81
false =====found=====
Test Suites: 1 failed, 1 total
Tests:       1 failed, 6 passed, 7 total

这是测试类和目标类。我正在扩展目标类以公开其所有方法进行测试。

ScriptTag.test.js：

test("exists() returns false for no matching scriptTag from fake fetch", async() => {
jest.spyOn(ScriptTagTester.prototype, "fetchAllScriptTags")
.mockResolvedValueOnce(dummyScriptTagsMissingTarget);
const scriptTagTester = new ScriptTagTester("","", "https://firebaseDomain.com/scriptTag.js");
await expect(scriptTagTester.exists()).toStrictEqual(false);
})

ScriptTag.ts：

protected async exists(): Promise<boolean> {
const scriptTags: ScriptTagObject[] = await this.fetchAllScriptTags();
const scriptTagFileNames: string[] = scriptTags.map((scriptTagRecord: ScriptTagObject) => {
const tagFileName: string = this.getFileName(scriptTagRecord.src);
return tagFileName;
});
// if has an index, return true, else false
console.log(scriptTagFileNames, `=====scriptTagFileNames=====`);
const fileIsFound: boolean = Boolean(scriptTagFileNames.indexOf(this.localFileName) > -1);
console.log(fileIsFound, `=====found=====`);
return fileIsFound;
}

Answer 1

从本文档中，您应该在函数expect后使用.resolves。

短安瑟：

await expect(scriptTagTester.exists()).resolves.toStrictEqual(false);

例如

ScriptTag.ts：

export interface ScriptTagObject {
src: string;
}
export class ScriptTag {
localFileName = 'b.js';
constructor(a, b, c) {}
protected async exists(): Promise<boolean> {
const scriptTags: ScriptTagObject[] = await this.fetchAllScriptTags();
const scriptTagFileNames: string[] = scriptTags.map((scriptTagRecord: ScriptTagObject) => {
const tagFileName: string = this.getFileName(scriptTagRecord.src);
return tagFileName;
});
console.log(scriptTagFileNames, `=====scriptTagFileNames=====`);
const fileIsFound: boolean = Boolean(scriptTagFileNames.indexOf(this.localFileName) > -1);
console.log(fileIsFound, `=====found=====`);
return fileIsFound;
}
protected async fetchAllScriptTags(): Promise<ScriptTagObject[]> {
return [{ src: 'a' }];
}
private getFileName(src) {
return src;
}
}

ScriptTag.test.ts：

import { ScriptTag, ScriptTagObject } from './ScriptTag';
class ScriptTagTester extends ScriptTag {
constructor(a, b, c) {
super(a, b, c);
}
}
describe('ScriptTag', () => {
test('exists() returns false for no matching scriptTag from fake fetch', async () => {
const dummyScriptTagsMissingTarget: ScriptTagObject[] = [
{ src: 'somescript.js' },
{ src: 'somescript2.js' },
{ src: 'somescript3.js' },
{ src: 'scriptTag.js' },
];
jest
.spyOn(ScriptTagTester.prototype as any, 'fetchAllScriptTags')
.mockResolvedValueOnce(dummyScriptTagsMissingTarget);
const scriptTagTester = new ScriptTagTester('', '', 'https://firebaseDomain.com/scriptTag.js');
await expect((scriptTagTester as any).exists()).resolves.toStrictEqual(false);
});
});

带有覆盖率报告的单元测试结果：

PASS  src/stackoverflow/59310993/ScriptTag.test.ts
ScriptTag
✓ exists() returns false for no matching scriptTag from fake fetch (18ms)
console.log src/stackoverflow/59310993/ScriptTag.ts:3266
[ 'somescript.js',
'somescript2.js',
'somescript3.js',
'scriptTag.js' ] '=====scriptTagFileNames====='
console.log src/stackoverflow/59310993/ScriptTag.ts:3274
false '=====found====='
--------------|----------|----------|----------|----------|-------------------|
File          |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
--------------|----------|----------|----------|----------|-------------------|
All files     |    94.44 |      100 |    83.33 |    93.75 |                   |
ScriptTag.ts |    94.44 |      100 |    83.33 |    93.75 |                25 |
--------------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        5.86s, estimated 16s

源代码：https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/59310993