generateTestFile() {
    let message = 'Please install an Ember.js test framework addon or update your dependencies.';

    if (this.ui) {
      this.ui.writeDeprecateLine(message);
    } else {
      console.warn(message);
    }

    return '';
  }
Generate test file contents.

    This method is supposed to be overwritten by test framework addons
    like `ember-qunit`.

    @public
    @method generateTestFile
    @param {String} moduleName Name of the test module (e.g. `JSHint`)
    @param {Object[]} tests Array of tests with `name`, `passed` and `errorMessage` properties
    @return {String} The test file content