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.