JavaScriptServices

Instructions provided by @ManuelDeLeon - thanks!

1) Modify package.json

1.1) Add the following to devDependencies:

    "http-server": "^0.9.0",
    "karma-remap-istanbul": "^0.2.1",
    "sourcemap-istanbul-instrumenter-loader": "^0.2.0"

http-server to easily show the generated html files. Running npm run coverage is easier than navigating to the root html file of the code coverage result.
karma-remap-istanbul to generate the report.
sourcemap-istanbul-instrumenter-loader to show original TypeScript files, not the transpiled ones.

1.2) Add the scripts to show the code coverage (the report is generated when you run the tests).

  "scripts": {
    "test": "karma start ClientApp/test/karma.conf.js",
    "test-single": "karma start ClientApp/test/karma.conf.js --single-run",
    "show-coverage": "npm run test-single && http-server -c-1 -o -p 9875 ClientApp/test/coverage"
  },

2) Modify ClientApp/test/boot-tests.ts to load all .ts files, othewise it will only show the code coverage for the components touched by test files.

const context = require.context('../app', true, /\.ts$/);

3) Modify ClientApp/test/karma.conf.js to generate the code coverage:

3.1) Update webpack config to use sourcemap-istanbul-instrumenter-loader:

var path = require('path');
var webpackConfig = require('../../webpack.config.js').filter(config => config.target !== 'node')[0];
webpackConfig.module.postLoaders = [{
    test: /\.ts$/,
    include: [path.resolve(__dirname, "../app")],
    loader: 'sourcemap-istanbul-instrumenter-loader?force-sourcemap=true',
    exclude: [/\.spec\.ts$/]
}];

3.2) Add the reporter and use our modified webpack config:

webpack: webpackConfig,
reporters: ['progress', 'karma-remap-istanbul'],
remapIstanbulReporter: {
    reports: {
        html: 'ClientApp/test/coverage'
    }
}

4) Update .gitignore so it ignores the coverage results:

/ClientApp/test/coverage/**

Result:

Sample repo:

https://github.com/ManuelDeLeon/jss-angular-code-coverage

Hope it helps.