}

    @Override
    public double slope() {
      return NaN;
    }

    @Override
    public double transform(double x) {
      return NaN;
    }

    @Override
    public LinearTransformation inverse() {
      return this;
    }

    @Override
    public String toString() {
      return "NaN";
    }
  }

  }

  public void testMapping_nanY1() {
    assertThrows(
        IllegalArgumentException.class, () -> LinearTransformation.mapping(1.2, Double.NaN));
  }

  public void testMappingAnd_nanX2() {
    assertThrows(
        IllegalArgumentException.class,
        () -> LinearTransformation.mapping(1.2, 3.4).and(Double.NaN, 7.8));
  }

  }

  public void testMapping_nanY1() {
    assertThrows(
        IllegalArgumentException.class, () -> LinearTransformation.mapping(1.2, Double.NaN));
  }

  public void testMappingAnd_nanX2() {
    assertThrows(
        IllegalArgumentException.class,
        () -> LinearTransformation.mapping(1.2, 3.4).and(Double.NaN, 7.8));
  }

      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testCheckNonNegative_nanFloat() {
    try {
      MathPreconditions.checkNonNegative("float", Float.NaN);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testCheckNonNegative_zeroDouble() {
    MathPreconditions.checkNonNegative("double", 0d);
  }

      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testCheckNonNegative_nanFloat() {
    try {
      MathPreconditions.checkNonNegative("float", Float.NaN);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testCheckNonNegative_zeroDouble() {
    MathPreconditions.checkNonNegative("double", 0d);
  }

    assertEquals(0.0, DoubleUtils.ensureNonNegative(Double.NEGATIVE_INFINITY));
    assertThrows(IllegalArgumentException.class, () -> DoubleUtils.ensureNonNegative(Double.NaN));
  }

  public void testOneBits() {
    assertEquals(DoubleUtils.ONE_BITS, Double.doubleToRawLongBits(1.0));
  }

  private static void failFormat(String template, Object... args) {

    assertEquals(0.0, DoubleUtils.ensureNonNegative(Double.NEGATIVE_INFINITY));
    assertThrows(IllegalArgumentException.class, () -> DoubleUtils.ensureNonNegative(Double.NaN));
  }

  public void testOneBits() {
    assertEquals(DoubleUtils.ONE_BITS, Double.doubleToRawLongBits(1.0));
  }

  private static void failFormat(String template, Object... args) {

    }
    return x;
  }

  @CanIgnoreReturnValue
  static double checkNonNegative(String role, double x) {
    if (!(x >= 0)) { // not x < 0, to work with NaN.
      throw new IllegalArgumentException(role + " (" + x + ") must be >= 0");
    }
    return x;
  }

  static void checkRoundingUnnecessary(boolean condition) {
    if (!condition) {