Provides a NPM module to add Istanbul instrumentation to JSPM / SystemJS by replacing the System.translate hook.

By using this module SystemJS can be instrumented for code coverage with Istanbul with minimal effort.

For a comprehensive ES6 build / testing / publishing NPM module please see typhonjs-npm-build-test as it combines this module along with transpiling ES6 sources with Babel, pre-publish script detection, ESDoc dependencies, testing with Mocha / Istanbul and an Istanbul instrumentation hook for JSPM / SystemJS tests.

Please review istanbul-jspm-coverage-example for a complete working example which uses typhonjs-npm-build-test and subsequently this module which is included as a dependency to typhonjs-npm-build-test.

In short an ES6 Mocha test that instruments Istanbul will do the following:

import jspm                      from 'jspm';

import instrumentIstanbulSystem  from 'typhonjs-istanbul-instrument-jspm';

// Set the package path to the local root where config.js is located.
jspm.setPackagePath(process.cwd());

// Create SystemJS Loader
const System = new jspm.Loader();

// Replaces System.translate with version that provides Istanbul instrumentation.
instrumentIstanbulSystem(System);

instrumentIstanbulSystem takes two parameters:

(object)   System - An instance of SystemJS.

(RegExp)   sourceFilePathRegex - (optional) A regex which defines which source files are instrumented; default excludes
                                 any sources with file paths that includes `jspm_packages`.

It should be noted that the default source file path regex is defined as /^((?!jspm_packages).)*$/ which excludes any sourcecode loaded from jspm_packages. You may optionally pass in a regex as the second parameter to instrumentIstanbulSystem. An example of excluding both jspm_packages and ./test/src is: instrumentIstanbulSystem(System, /^((?!jspm_packages|test\/src\/).)*$/);.

A final important detail when using Istanbul is that the cover command will not pickup the source instrumented via typhonjs-istanbul-instrument-jspm when an initial report is generated, however the instrumentation is represented in coverage.raw.json. To make sure SystemJS sources are represented in the final report simply run the Istanbul report command and the original source will be included in the report. This is automated by the mocha-istanbul-report NPM script that is included as part of typhonjs-npm-build-test / typhonjs-npm-scripts-test-mocha.

In package.json add an NPM script like the following:

"scripts": {
  "test-coverage": "babel-node ./node_modules/typhonjs-npm-scripts-test-mocha/scripts/mocha-istanbul-report.js"
}

Please note that the TyphonJS NPM scripts use a separate configuration file ./npmscriptrc to define various actions. For further information refer to typhonjs-npm-scripts-test-mocha