// karma.conf.js
module.exports = function(config) {
  config.set({

    basePath: '',

    frameworks: ['mocha', 'chai'],

    files: [
      // '__test__/**/*.spec.js'
      'test.webpack.js'      
    ],

    exclude: [
      '**/*.swp',
      'src/router.config.js'
    ],


    preprocessors: {
      'test.webpack.js': ['webpack', 'coverage'],
    },

    webpack: {
      devtool: 'inline-source-map',
      resolve: {
        extensions: ['.js', '.jsx'],
      },
      module: {
        rules: [{
          test: /\.jsx?$/,
          use: {
            loader: 'babel-loader',
            options: {
              presets: ['react', 'es2015', 'stage-0'],
              plugins: ['transform-runtime']
            },
          },
          exclude: /(node_modules|bower_components)/,
        },]
      },
    },
    webpackMiddleware: {
      noInfo: true
    },

    reporters: ['mocha', 'coverage'],

    port: 9876,

    colors: true,

    logLevel: config.LOG_INFO,

    autoWatch: true,

    browsers: ['Chrome'],

    singleRun: false,

    concurrency: Infinity,

    coverageReporter: {
      reporters:[
        {type: 'html', dir: 'coverage/'},
        {type: 'text-summary'}
      ],
    }
  })
}

// __test__/demo.spec.js
import React from 'react';
import { expect } from 'chai';
import TestUtils from 'react-dom/test-utils';

class Common extends React.Component {
  render() {
    return (
      <div>hello world</div>
    )
  }
}

describe('test component', () => {
  it('test demo component', () => {
    const renderer = TestUtils.createRenderer();
    renderer.render(<Common />);
    const output = renderer.getRenderOutput();
    console.log(output); // NOTE! If i delete this code. Karma will be ok. But why can't i console this result and how to fix this?
  })
})