How to config gulp to run unit test cases using Istanbul with code coverage

Add below configuration in gulpfile.js for running Istanbul with mocha unit test cases through gulp.

const gulp = require('gulp');
const istanbul = require('gulp-istanbul');
const mocha = require('gulp-mocha');

gulp.task('test', () => {    
 gulp.src(['src/**/*.js'])
    .pipe(istanbul())
    .pipe(istanbul.hookRequire())
    .on('finish', () => {
      gulp.src(['test/unit/**/*.spec.js'])
        .pipe(mocha())
        .pipe(istanbul.writeReports({
          dir: './test/unit-test-coverage',
          reporters: ['lcov', 'clover', 'text', 'text-summary'],
          reportOpts: {
            dir: './test/unit-test-coverage',
          },
        }));        
    });
 });

For code coverage, we can use istanbul.writeReports method as shown above.

Once executing the command gulp test, it will execute all the test cases along with coverage report generated at given location.

Running Jest using Gulp with code coverage

Jest is a unit test framework that is mainly used for reactjs. Jest is widely used by facebook in their projects.

Add below configuration in gulpfile.js for running Jest unit test cases through gulp

  const gulp = require('gulp');
  const jestcli = require('jest-cli');

  gulp.task('test', () => {  
   jestcli.runCLI({ config: { rootDir: 'test/unit/' } }, '.', (done) => {
    done();
   });
  });

Using command: gulp test, will execute the test cases written under directory 'test/unit'. To have code coverage, we can configure it in package.json file as below:

  "jest": {
    "collectCoverage": true,
    "coverageDirectory": "./test/unit-test-coverage"
  }

Add above config in package.json file. for defining custom directory to create the report, mention the directory in coverageDirectory key, otherwise it will generate at root directory.