static createMockAudioStream(id) {
    const ContentType = shaka.util.ManifestParserUtils.ContentType;
    const Util = shaka.test.Util;

    const mimeType = 'audio/mp4';
    const codecs = 'mp4a.40.2';
    return {
      id: id,
      originalId: id.toString(),
      groupId: null,
      createSegmentIndex: Util.spyFunc(jasmine.createSpy('createSegmentIndex')),
      closeSegmentIndex: Util.spyFunc(jasmine.createSpy('closeSegmentIndex')),
      segmentIndex: null,
      mimeType,
      codecs,
      bandwidth: 192000,
      type: ContentType.AUDIO,
      label: '',
      language: 'und',
      originalLanguage: null,
      drmInfos: [],
      encrypted: false,
      keyIds: new Set(),
      audioSamplingRate: 44100,
      channelsCount: 2,
      closedCaptions: null,
      emsgSchemeIdUris: null,
      primary: false,
      roles: [],
      forced: false,
      spatialAudio: false,
      accessibilityPurpose: null,
      external: false,
      fastSwitching: false,
      fullMimeTypes: new Set([shaka.util.MimeUtils.getFullType(
          mimeType, codecs)]),
      isAudioMuxedInVideo: false,
      baseOriginalId: null,
    };
  }
Creates a mock audio Stream.

@param {number} id
@return {shaka.extern.Stream}