Config karma.conf.js to show code coverage report and clean every-time to run server. ( Then just run unit test and it will auto-generate file by istanbul engine )

A-config-to-clean-everytime-test-report-generated.js

clean: {
      dist: {
        files: [{
          dot: true,
          src: [
            '.tmp',
            '<%= yeoman.dist %>/*',
            '!<%= yeoman.dist %>/.git*'
          ]
        }]
      },
      //clear folder coverage
      server: ['.tmp','coverage']
    },

Config-karma-to-show-report.js

//add report coverage
preprocessors = {
    'app/scripts/**/*.js': 'coverage'
}

//coverage report
coverageReporter = {
    type : 'html',
    dir : 'coverage/'
}

gitignore.txt

//Don't forget to ignore this folder before push it
coverage

Gruntfiles.js

grunt.registerTask('server', function (target) {
    if (target === 'dist') {
      return grunt.task.run(['build', 'open', 'connect:dist:keepalive']);
    }

    grunt.task.run([
      //when run server it will clean folder coverage automatic
      'clean:server',
      'replace:local',
      'karma:unit',
      'concurrent:server',
      'connect:livereload',
      'open',
      'watch'
    ]);
    
  });