如何在Node.js中测试流的错误？

Question

我有一个创建md5的函数，并且我已经创建了一个检查其行为的测试，脚本可以工作。现在我需要创建一个测试来检查当createHash()或createReadStream()失败时承诺是否被拒绝。

如何测试这种情况，有什么最佳实践？如果您能发布一个示例，我将不胜感激！

export const md5 = (path: string) =>
  new Promise<string>((resolve, reject) => {
    const hash = createHash("md5");
    const rs = createReadStream(path);
    rs.on("error", reject);
    rs.on("data", chunk => hash.update(chunk));
    rs.on("end", () => resolve(hash.digest("hex")));
  });

---

describe("md5", () => {
  const fileName = `${TEST_DIR}/file1.txt`;

  beforeAll(() => createFile(fileName));

  afterAll(() => removeFile(TEST_DIR));

  it("should hash md5 a file", () => {
    md5(fileName).then((hash: string) => {
      assert.strictEqual(hash, "4738e449ab0ae7c25505aab6e88750da");
    });
  });
});

- Radex

Answer 1

我需要创建一个测试来检查 Promise 是否被拒绝。

尝试下面的代码：Jasmine 的 it 块的第二个参数是一个函数，它有一个传递给它的参数 done。 done 是一个函数，用户可以调用它来使测试通过。如果在超时窗口内没有调用 done，Jasmine 将认为测试失败。

stream-reader.js

const fs = require('fs')

const createReader = inputFile => {
  const reader = fs.createReadStream(inputFile, {encoding: 'utf8'})
  const result = new Promise((resolve, reject) => {
    reader.on('error', e => reject(e))
  })

  // return 2 things...
  return {
    reader,  // ...a stream that broadcasts chunks over time
    result,  // ...a Promise to be resolved on reading is done or error encountered
  }
}

module.exports = createReader

spec.js

const streamReader = require('../stream-reader')
const INPUT_FILE = './input1.txt'

describe('streamReader', () => {
    it(`should pass a chunk of the file on 'data' event`, (done) => {
        const api = streamReader(INPUT_FILE)
        api.reader.on('data', (chunk) => {
            console.log('[JASMINE TEST 1] received', chunk)
            done()
        })
    })

    /* test Promise.reject on stream error */
    it(`should reject on case of reading errors`, (done) => {
        const api = streamReader('./non/existent/file')
        api.result.catch(e => {
            console.log('[JASMINE TEST 2] correctly rejected')
            done()
        })
    })
})

输出

$ npm test

> so-jasmine-test@1.0.0 test C:\Users\jonathanlopez\nodejs\so-stream-reject
> jasmine

Randomized with seed 22758
Started
[JASMINE TEST 1] received the quick brown fox
.[JASMINE TEST 2] correctly rejected
.


2 specs, 0 failures
Finished in 0.026 seconds
Randomized with seed 22758 (jasmine --random=true --seed=22758)

希望这能有所帮助。 祝好。

- jonathangersam

Answer 2

你可以使用md5函数来处理错误，方法如下：

md5('bad_path').catch((error: Error) => {
  assert.strictEqual(error.message.length > 0, true);
});

- GibboK