### Question:
InitialStateCalculator { protected RealMatrix calculateZIN() { RealMatrix identityMatrix = MatrixUtils.createRealIdentityMatrix(numberOfCoefficients-1); RealMatrix subtrahend = calculateSubtrahendForZIN(); return identityMatrix.subtract(subtrahend); } InitialStateCalculator(FilterCoefficients filterCoefficients); double[] getInitialState(); double[] growSignal(double[] signal); double[] growSignal(double[] signal, boolean leftOnly);  }### Answer:
@Test public void testCalculateZIN() { InitialStateCalculator calculator = new InitialStateCalculator(getSampleFilterCoefficients1()); RealMatrix actual = calculator.calculateZIN(); RealMatrix expected = new Array2DRowRealMatrix(new double[][] { {-1.6861574, - 1, 0}, {2.41965511, 1, -1,}, {-0.73016535, 0, 1} }); assertMatrixEquals(expected, actual, 1e-7); calculator = new InitialStateCalculator(getSampleFilterCoefficients2()); actual = calculator.calculateZIN(); expected = new Array2DRowRealMatrix(new double[][] { {1.11, - 1, 0, 0, 0}, {-0.5, 1, -1, 0, 0}, {0, 0, 1, -1, 0}, {0, 0, 0, 1, -1}, {0, 0, 0, 0, 1} }); assertMatrixEquals(expected, actual, 1e-7); }