for (double d : Arrays.asList(Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, Double.NaN)) {
      assertFalse(DoubleMath.isMathematicalInteger(d));
    }
  }

  @GwtIncompatible // Math.ulp
  public void testFactorial() {
    for (int i = 0; i <= DoubleMath.MAX_FACTORIAL; i++) {
      double actual = BigIntegerMath.factorial(i).doubleValue();
      double result = DoubleMath.factorial(i);

      fail("Expected for " + a + " " + op + " " + b + " = " + expected + ", but got " + actual);
    }
  }

  // Depends on the correctness of BigIntegerMath.factorial.
  @GwtIncompatible // TODO
  public void testFactorial() {
    for (int n = 0; n <= 50; n++) {
      BigInteger expectedBig = BigIntegerMath.factorial(n);
      long expectedLong = fitsInLong(expectedBig) ? expectedBig.longValue() : Long.MAX_VALUE;