testYiqBrightness() {
    const white = [255, 255, 255];
    const black = [0, 0, 0];
    const coral = [255, 127, 80];
    const lightgreen = [144, 238, 144];

    const whiteBrightness = googColor.yiqBrightness_(white);
    const blackBrightness = googColor.yiqBrightness_(black);
    const coralBrightness = googColor.yiqBrightness_(coral);
    const lightgreenBrightness = googColor.yiqBrightness_(lightgreen);

    // brightness should be a number
    assertTrue(
        'White brightness is a number.', typeof whiteBrightness == 'number');
    assertTrue(
        'Coral brightness is a number.', typeof coralBrightness == 'number');

    // brightness for known colors should match known values
    assertEquals('White brightness is 255', whiteBrightness, 255);
    assertEquals('Black brightness is 0', blackBrightness, 0);
    assertEquals('Coral brightness is 160', coralBrightness, 160);
    assertEquals('Lightgreen brightness is 199', lightgreenBrightness, 199);
  }
This method runs unit tests against googColor.yiqBrightness_().
@suppress {visibility} accessing private properties