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?

Inigo · Accepted Answer · 2022-04-27 07:14:13Z

18

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"

edited Apr 27, 2022 at 7:14

Inigo

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answered Sep 28, 2020 at 15:25

MatiasG

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Comments

Thomas Dondorf · Accepted Answer · 2018-11-01 13:12:45Z

13

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.

answered Nov 1, 2018 at 13:12

Thomas Dondorf

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1 Comment

sorin Over a year ago

This code does not compile with typescript in strict mode because currentTest property is missing.

ScottS · Accepted Answer · 2023-09-11 23:56:47Z

0

Using `sinon`

Another answer here (currently accepted as of this posting) can be refactored to use the sinon stubbing library, like so:

const sinon = require('sinon');

let consoleOutput;  

beforeEach(function () {
  consoleOutput = '';
  sinon.stub(console, 'log').callsFake((msg) => {
    consoleOutput += msg + '\n';
  });
});

afterEach(function () {
  sinon.restore();
  if (this.currentTest.state === 'failed') {
    console.log(consoleOutput);
  }
});

answered Sep 11, 2023 at 23:56

ScottS

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Comments

sorin · Accepted Answer · 2024-04-19 12:04:16Z

0

IMHO, the way to do this is to log only when assert fails, like:

Before

console.log(foo);
assert.equal(1, 2);

After

assert.equal(1, 2, foo);

answered Apr 19, 2024 at 12:04

sorin

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