Sass unit tests
JavaScript CSS Ruby Makefile
Latest commit d1dc0bd Dec 22, 2016 @mirisuzanne mirisuzanne Bump version 2.1.4


Build Status


  1. To make true; shape, adjust, place, etc., exactly or accurately: True the wheels of a bicycle after striking a pothole.
  2. To make even, symmetrical, level, etc. (often followed by up): True up the sides of a door.
  3. To test your Sass code; debug, perfect, etc. (often using True): True your sweet plugin before you deploy.


in command line:

# ruby gem
gem install true

# bower package
bower install true

# npm module
npm install sass-true


With any Sass compiler

@import "true";

@include test-module('Utilities') {

  // Testing Functions
  @include test('Map Add [function]') {
    $base: (one: 1, two: 1, three: 1);
    $add: (one: 1, two: 2, three: -1);

    $test: map-add($base, $add);
    $expect: (one: 2, two: 3, three: 0);
    @include assert-equal($test, $expect,
      'Returns the sum of two numeric maps');

  // Testing Mixins
  @include test('Font Size [mixin]') {
    @include assert('Outputs a font size and line height based on keyword.') {
      @include output {
        @include font-size(large);

      @include expect {
        font-size: 2rem;
        line-height: 3rem;

// Optionally show summary report in CSS and/or the command line:
// - If you use Mocha, reporting to the command line is automatic.
// - if you use true-cli, report(terminal) is required for output.
@include report;

Note: Function unit-tests work across the board, but testing mixins can be a bit more complex. At this point, only Mocha is able to compare/report the results of mixin tests. Without using Mocha, you can test any mixin, but you will have to compare the expected and actual results manually in the output code. Version control can make that much easier than it sounds.

With node-sass and Mocha (or other JS test runners)

  1. Install true via npm (npm install sass-true).

  2. Write some Sass tests in test/test.scss (see above).

  3. Write a shim JS test file in test/test_sass.js:

    var path = require('path');
    var sassTrue = require('sass-true');
    var sassFile = path.join(__dirname, 'test.scss');
    sassTrue.runSass({file: sassFile}, describe, it);
  4. Run Mocha, and see your Sass tests reported as individual test results.

You can call runSass more than once, if you have multiple Sass test files you want to run separately.

The first argument to runSass accepts the same options that node-sass' renderSync function accepts. The only modification runSass makes is to add True's sass path to the includePaths option, so @import 'true'; works in your Sass test file.

Any other JS test runner with equivalents to Mocha's describe and it should be usable in the same way; just pass your test runner's describe and it equivalents into runSass.

With Grunt...

Run Mocha using the Grunt task supplied by grunt-mocha-cli

Install grunt-mocha-cli:

npm install grunt-mocha-cli --save-dev

Configure task:


mochacli: {
   all: ['test/test_sass.js']

Run tests:

grunt mochacli

With ruby-sass on the command line

true-cli [options] PATH


  • -s silent
  • -c config file
  • -d debug config file settings

Config file (optional):

  color: true  # enables colored output

# require ruby sass extension libraries
  - "compass"
  - "serialy_sassy"

default location: test/true.yml


There is only one setting: $true-terminal-output toggles output to the terminal on or off.

  • true will show detailed information on failing assertions. This is the default, and best for using true-cli.
  • false to turn off all terminal output.