@aoberoi/capture-console

Capture Console

This is a utility, mostly used for testing, to capture string data written to both the stdout and stderr streams in Node.js applications.

NOTE: This project is forked from Randy Carver's capture-stdout. Many thanks to him and the others who helped that make that project exist. I forked it because I had more specialized needs, but might one day want to merge the fork back in.

Installation

npm install @aoberoi/capture-console

Usage

const { CaptureConsole } = require('@aoberoi/capture-console');

// Consider testing this function...
function withMinOfFive(x) {
  if (x < 5) {
    console.warn('rounding up to 5');
    return 5;
  } else {
    console.log('already more than 5');
    return x;
  }
}

// Let's pretend the logging behavior is very meaningful, and you want to verify it
it('should log when the value is already greater than 5', function() {
  // Start capturing
  const captureConsole = new CaptureConsole();
  captureConsole.startCapture();

  // invoke the function
  const result = withMinOfFive(10);

  // Stop capturing and read the output
  captureStdout.stopCapture();
  const output = captureStdout.getCapturedText();

  assert.equal(result, 10);

  // Verify that there's exactly one log line
  assert.equal(output.length, 1);
});

// `console.warn()` writes to stderr, but you can use the same methods to find that output as well
it('should warn when the value is less than 5', function() {
  // Start capturing
  const captureConsole = new CaptureConsole();
  captureConsole.startCapture();

  // invoke the function
  const result = withMinOfFive(3);

  // Stop capturing and read the output
  captureStdout.stopCapture();
  const output = captureStdout.getCapturedText();

  assert.equal(result, 5);

  // Verify that there's exactly one log line
  assert.equal(output.length, 1);
});

Methods

startCapture()

Starts capturing the writes to process.stdout and process.stderr.

stopCapture()

Stops capturing the writes to process.stdout and process.stderr.

clearCaptureText()

Clears all of the captured text.

getCapturedText() → {Array} of String

Returns all of the captured text.

Changes since Capture Stdout

• In addition to capturing stdout, also captures stderr
• Exports a namespace instead of a value (better interop with ESM imports)
• Made the README more generic
• Stated support back to currently active LTS (v6)
• Removes pino from tests