使用jest编写带有流的测试

npm install jest --save-dev

const fs = require('fs');
const { Transform } = require('stream');

test('transform stream', (done) => {
  const uppercaseTransform = new Transform({
    transform(chunk, encoding, callback) {
      this.push(chunk.toString().toUpperCase());
      callback();
    }
  });

  const sourceData = 'hello world';
  const expectedData = 'HELLO WORLD';

  const writableStream = fs.createWriteStream('output.txt');
  writableStream.on('finish', () => {
    const output = fs.readFileSync('output.txt', 'utf8');
    expect(output).toBe(expectedData);
    done();
  });

  const readableStream = new Readable({
    read() {
      this.push(sourceData);
      this.push(null);
    }
  });

  readableStream.pipe(uppercaseTransform).pipe(writableStream);
});

npx jest stream.test.js