### Question:
FourierTransform { public static double[] padWithZeroIfNecessary(double[] signal) { int powerOfTwoSize = getPowerOfTwoSize(signal.length); if (powerOfTwoSize != signal.length) { return ArrayOperations.padArrayWithZerosToSize(signal, powerOfTwoSize); } else { return signal; } } FourierTransform(WindowType windowType, double parameter);  FourierTransform(WindowType windowType);  FourierTransform(); Complex[] forwardFFT(double[] signal); double[] inverseFFT(Complex[] fft); static int getPowerOfTwoSize(int initialSize); static double[] padWithZeroIfNecessary(double[] signal); static double[] getFrequencies(double[] signal, double samplingFrequency); double[] calculatePowerSpectrum(double[] samples);  }### Answer:
@Test public void testPadWithZeroIfNecessary() { double[] signal = new double[] {1, 2, 3, 4, 5}; double[] paddedSignal = FourierTransform.padWithZeroIfNecessary(signal); double[] expected = new double[] {1, 2, 3, 4, 5, 0, 0, 0}; assertArrayEquals(expected, paddedSignal, 1e-5); signal = new double[] {1, 2, 3, 4}; paddedSignal = FourierTransform.padWithZeroIfNecessary(signal); expected = new double[] {1, 2, 3, 4}; assertArrayEquals(expected, paddedSignal, 1e-5); }