@Test
public void testFahrenheitToCelsius() {
    for (double knownCelsius : conversionTable.keySet()) {
        double knownFahrenheit = conversionTable.get(knownCelsius);

        double resultCelsius = TemperatureConverter.fahrenheitToCelsius(knownFahrenheit);

        double delta = Math.abs(resultCelsius - knownCelsius);
        String msg = knownFahrenheit + "F -> " + knownCelsius + "C “ + “but is " + resultCelsius;
        assertTrue(msg, delta < 0.0001);
}
