assertEquals(a, LongMath.gcd(a, 0));
      assertEquals(a, LongMath.gcd(0, a));
    }
    assertEquals(0, LongMath.gcd(0, 0));
  }

  @GwtIncompatible // TODO
  public void testGCDNegativePositiveThrows() {
    for (long a : NEGATIVE_LONG_CANDIDATES) {
      assertThrows(IllegalArgumentException.class, () -> LongMath.gcd(a, 3));
      assertThrows(IllegalArgumentException.class, () -> LongMath.gcd(3, a));
    }