CODEWITHSUNDEEP
javascriptnode.jsjestjs
John
John

Reputation: 355

How to create a broken stream for a test?

I have this function and I want to test it. I want to test stream.on('error', err => reject(err)); line, but don't know how to reach it. What could I input in this function to trigger the error throw? Thank you!

function streamToString(stream) {
  const chunks = [];
  return new Promise((resolve, reject) => {
    stream.on('data', chunk => chunks.push(Buffer.from(chunk)));
    stream.on('error', err => reject(err));
    stream.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
  });
}

Upvotes: 1

Views: 266

Answers (1)

DiniFarb
DiniFarb

Reputation: 206

If you are in nodejs and using jest you could Emit the error by your self like:


function streamToString(stream) {
  const chunks = [];
  return new Promise((resolve, reject) => {
    stream.on("data", (chunk) => chunks.push(Buffer.from(chunk)));
    stream.on("error", (err) => reject(err));
    stream.on("end", () => resolve(Buffer.concat(chunks).toString("utf8")));
  });
}

test("broken stream", () => {
  let fs = require("fs");
  let stream = fs.createReadStream("file.txt");
  let res = streamToString(stream);
  stream.emit("error", "OH NO!");
  return expect(res).rejects.toMatch("OH NO!");
});

//or

test("broken stream", () => {
  let fs = require("fs");
  let stream = fs.createReadStream("file.txt");
  let res = streamToString(stream);
  stream.destroy("OH NO!");
  return expect(res).rejects.toMatch("OH NO!");
});

Upvotes: 1

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