karma-coverage

What is karma-coverage?

The karma-coverage npm package is a plugin for the Karma test runner that generates code coverage reports. It uses Istanbul under the hood to instrument the code and then record the coverage data when the tests are run. The reports can be generated in various formats and can be integrated into continuous integration workflows to ensure code quality.

What are karma-coverage's main functionalities?

Coverage Reporting

This feature allows you to generate coverage reports in various formats such as HTML, LCOV, and JSON. The code sample shows how to configure Karma to use the karma-coverage plugin to generate an HTML coverage report.

module.exports = function(config) {
  config.set({
    // other Karma configuration...
    reporters: ['progress', 'coverage'],
    preprocessors: {
      '**/*.js': ['coverage']
    },
    coverageReporter: {
      type : 'html',
      dir : 'coverage/'
    }
  });
};

Threshold Enforcement

This feature allows you to enforce coverage thresholds. If the code does not meet the specified thresholds for statements, branches, functions, or lines, Karma will exit with an error. The code sample demonstrates how to set these thresholds in the Karma configuration.

module.exports = function(config) {
  config.set({
    // other Karma configuration...
    reporters: ['progress', 'coverage'],
    coverageReporter: {
      check: {
        global: {
          statements: 80,
          branches: 80,
          functions: 80,
          lines: 80
        }
      }
    }
  });
};

Other packages similar to karma-coverage

nyc

nyc is the official Istanbul command line interface. It can produce coverage reports similar to karma-coverage but is more often used with Node.js applications directly, rather than through a test runner like Karma.

jest

Jest is a testing framework that includes its own coverage reporting capabilities. It is an alternative to using Karma with karma-coverage, offering a more integrated solution with a focus on simplicity and ease of use.

c8

c8 is a Node.js code coverage tool built on top of V8's built-in coverage. It is similar to nyc but uses the native coverage features of V8, providing potentially more accurate coverage information for Node.js applications.

README

karma-coverage

Generate code coverage using Istanbul.

Installation

The easiest way is to install karma-coverage as a devDependency, by running

npm install karma karma-coverage --save-dev

Configuration

For configuration details see docs/configuration.

Examples

Basic

// karma.conf.js
module.exports = function(config) {
  config.set({
    files: [
      'src/**/*.js',
      'test/**/*.js'
    ],

    // coverage reporter generates the coverage
    reporters: ['progress', 'coverage'],

    preprocessors: {
      // source files, that you wanna generate coverage for
      // do not include tests or libraries
      // (these files will be instrumented by Istanbul)
      'src/**/*.js': ['coverage']
    },

    // optionally, configure the reporter
    coverageReporter: {
      type : 'html',
      dir : 'coverage/'
    }
  });
};

CoffeeScript

For an example on how to use with CoffeeScript see examples/coffee. For an example of how to use with CoffeeScript and the RequireJS module loader, see examples/coffee-requirejs (and also see the useJSExtensionForCoffeeScript option in docs/configuration.md).

Advanced, multiple reporters

// karma.conf.js
module.exports = function(config) {
  config.set({
    files: [
      'src/**/*.js',
      'test/**/*.js'
    ],
    reporters: ['progress', 'coverage'],
    preprocessors: {
      'src/**/*.js': ['coverage']
    },
    coverageReporter: {
      // specify a common output directory
      dir: 'build/reports/coverage',
      reporters: [
        // reporters not supporting the `file` property
        { type: 'html', subdir: 'report-html' },
        { type: 'lcov', subdir: 'report-lcov' },
        // reporters supporting the `file` property, use `subdir` to directly
        // output them in the `dir` directory
        { type: 'cobertura', subdir: '.', file: 'cobertura.txt' },
        { type: 'lcovonly', subdir: '.', file: 'report-lcovonly.txt' },
        { type: 'teamcity', subdir: '.', file: 'teamcity.txt' },
        { type: 'text', subdir: '.', file: 'text.txt' },
        { type: 'text-summary', subdir: '.', file: 'text-summary.txt' },
      ]
    }
  });
};

FAQ

Don't minify instrumenter output

When using the istanbul instrumenter (default), you can disable code compaction by adding the following to your configuration.

// karma.conf.js
module.exports = function(config) {
  config.set({
    coverageReporter: {
      instrumenterOptions: {
        istanbul: { noCompact: true }
      }
    }
  });
};

---

For more information on Karma see the homepage.

Changelog

2.2.1 (2023-06-23)

Bug Fixes

• exit code when reporter file is not provided (1388186)

Features

• update Istanbul packages (24aac11)