Mocha: Hide console.log output from successful tests

Question

My Problem

I'm writing a test suite for a Node.js application using Mocha. The functions that I'm testing write their logs to console.log directly, without any third-party logging solution.

I don't care about logs from successful tests, just from failed tests, and since my functions are pretty verbose the test output is unnecessarily long.

What Have I Tried

• SFTW. Found this (Suppress console log of successful mocha tests), but it refers to Winston logs.

My Question

How can I suppress console.log output from passing / successful Mocha tests?

Answer 1

You can modify the console.log function to log its argument to a variable:

const originalLogFunction = console.log;
let output;
beforeEach(function(done) {
  output = '';
  console.log = (msg) => {
    output += msg + '\n';
  };
});

afterEach(function() {
  console.log = originalLogFunction; // undo dummy log function
  if (this.currentTest.state === 'failed') {
    console.log(output);
  }
});

You might need to modify the dummy log function in case you are supplying more than one argument or objects. This is a simplified example.

Answer 2

This is utterly simple with Mocha Suppress Logs.

Just install it:

npm install --save-dev mocha-suppress-logs

and EITHER add it to your Mocha command:

mocha --require mocha-suppress-logs

OR put this in your Mocha config to make it the default:

"require": "mocha-suppress-logs"