title: Why is the Karma configuration file exclude option is not working?
body: <p>I have two spec files in my sample Angular app. The spec files names are 
  <code>src/app/app.component.spec.ts</code> &amp; <code>src/app/app.component-two.spec.ts</code>. I want to run only the tests in file <code>src/app/app.component.spec.ts</code>. So, I added the other file as exclude in the <code>karma.conf.js</code> file (pasted below), still the tests mentioned in the exclude option are being executed.
  Any help is greatly appreciated.</p>
  
  <pre><code>// Karma configuration file, see link for more information
  // https://karma-runner.github.io/1.0/config/configuration-file.html
  
  module.exports = function (config) {
    config.set({
      basePath: '',
      exclude: [
        'src/app/app.component-two.spec.ts'
      ],
      frameworks: ['jasmine', '@angular/cli'],
      plugins: [
        require('karma-jasmine'),
        require('karma-chrome-launcher'),
        require('karma-jasmine-html-reporter'),
        require('karma-coverage-istanbul-reporter'),
        require('@angular/cli/plugins/karma')
      ],
      client:{
        clearContext: false // leave Jasmine Spec Runner output visible in browser
      },
      coverageIstanbulReporter: {
        reports: [ 'html', 'lcovonly' ],
        fixWebpackSourcePaths: true
      },
      angularCli: {
        environment: 'dev'
      },
      reporters: ['progress', 'kjhtml'],
      port: 9876,
      colors: true,
      logLevel: config.LOG_INFO,
      autoWatch: true,
      browsers: ['Chrome'],
      singleRun: false
    });
  };
  </code></pre>