old_contents: /**
   * Copyright 2016 Google Inc. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  const Audit = require('../../../src/audits/audit.js');
  const assert = require('assert');
  
  'use strict';
  
  /* eslint-env mocha */
  
  // Extend the Audit class but fail to implement meta. It should throw errors.
  class A extends Audit {}
  class B extends Audit {
    static get meta() {
      return {};
    }
  }
  
  describe('Audit', () => {
    it('throws if an audit does not override the meta', () => {
      assert.throws(_ => A.meta);
    });
  
    it('does not throw if an audit overrides the meta', () => {
      assert.doesNotThrow(_ => B.meta);
    });
  
    it('throws if an audit does generate a result with a value', () => {
      assert.throws(_ => A.generateAuditResult({}));
    });
  });
  
new_contents: /**
   * Copyright 2016 Google Inc. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  'use strict';
  
  const Audit = require('../../../src/audits/audit.js');
  const assert = require('assert');
  
  /* eslint-env mocha */
  
  // Extend the Audit class but fail to implement meta. It should throw errors.
  class A extends Audit {}
  class B extends Audit {
    static get meta() {
      return {};
    }
  }
  
  describe('Audit', () => {
    it('throws if an audit does not override the meta', () => {
      assert.throws(_ => A.meta);
    });
  
    it('does not throw if an audit overrides the meta', () => {
      assert.doesNotThrow(_ => B.meta);
    });
  
    it('throws if an audit does generate a result with a value', () => {
      assert.throws(_ => A.generateAuditResult({}));
    });
  });
  
subject: fix strict mode in test/audits/audit.js