double y = 1.2;
    LinearTransformation transformation = LinearTransformation.horizontal(y);
    assertHorizontalLinearTransformation(transformation, y);
  }

  public void testHorizontal_infiniteY() {
    assertThrows(
        IllegalArgumentException.class,
        () -> LinearTransformation.horizontal(Double.POSITIVE_INFINITY));
  }

  public void testHorizontal_nanY() {

    double y = 1.2;
    LinearTransformation transformation = LinearTransformation.horizontal(y);
    assertHorizontalLinearTransformation(transformation, y);
  }

  public void testHorizontal_infiniteY() {
    assertThrows(
        IllegalArgumentException.class,
        () -> LinearTransformation.horizontal(Double.POSITIVE_INFINITY));
  }

  public void testHorizontal_nanY() {

   * (The inverse of this will be a horizontal transformation.)
   */
  public static LinearTransformation vertical(double x) {
    checkArgument(isFinite(x));
    return new VerticalLinearTransformation(x);
  }

  /**
   * Builds an instance representing a horizontal transformation with a constant value of {@code y}.

   * the XML specification.
   *
   * <p>This escaper does not escape non-ASCII characters to their numeric character references
   * (NCR). However, horizontal tab {@code '\t'}, line feed {@code '\n'} and carriage return {@code
   * '\r'} are escaped to a corresponding NCR {@code "&#x9;"}, {@code "&#xA;"}, and {@code "&#xD;"}