assertEquals(expected.toBigInteger(), DoubleMath.roundToBigInteger(d, UNNECESSARY));
    }
  }

  @GwtIncompatible // DoubleMath.roundToBigInteger(double, RoundingMode)
  public void testRoundExactFractionalDoubleToBigIntegerFails() {
    for (double d : FRACTIONAL_DOUBLE_CANDIDATES) {
      assertThrows(ArithmeticException.class, () -> DoubleMath.roundToBigInteger(d, UNNECESSARY));
    }
  }

    BigInteger maxDoubleAsBigInteger = DoubleMath.roundToBigInteger(Double.MAX_VALUE, UNNECESSARY);
    new RoundToDoubleTester(maxDoubleAsBigInteger)
        .setExpectation(Double.MAX_VALUE, values())
        .test();
  }

  @J2ktIncompatible
  @GwtIncompatible
  public void testRoundToDouble_maxDoublePlusOne() {
    BigInteger maxDoubleAsBigInteger =
        DoubleMath.roundToBigInteger(Double.MAX_VALUE, UNNECESSARY).add(BigInteger.ONE);

    } while (sqrt1.compareTo(sqrt0) < 0);
    return sqrt0;
  }

  @GwtIncompatible // TODO
  private static BigInteger sqrtApproxWithDoubles(BigInteger x) {
    return DoubleMath.roundToBigInteger(Math.sqrt(DoubleUtils.bigToDouble(x)), HALF_EVEN);
  }

  /**
   * Returns {@code x}, rounded to a {@code double} with the specified rounding mode. If {@code x}