ExtractUpper() public method

Returns Matrix with only the values in the main diagonal and upper triangle (above main diagonal) intact. Has 0.0's in lower triangle
public ExtractUpper ( ) : Matrix
return Matrix
        public void Matrix_ExtractUpperComplicatedTest()
        {
            Matrix matrixA = new Matrix(4, 4);

            //Set up matrix A
            double[] columnOneOfMatrixA = { 3, 1, 2, 5 };
            double[] columnTwoOfMatrixA = { 7, 8, 1, 4 };
            double[] columnThreeOfMatrixA = { 2, 4, 9, 7 };
            double[] columnFourOfMatrixA = { 5, 2, 3, 1 };

            matrixA.SetColumn(0, columnOneOfMatrixA);
            matrixA.SetColumn(1, columnTwoOfMatrixA);
            matrixA.SetColumn(2, columnThreeOfMatrixA);
            matrixA.SetColumn(3, columnFourOfMatrixA);

            //The LUP Decomposition

            //Correct U Part
            Matrix correctUPartOfLUPDecomposition = new Matrix(4, 4);

            double[] columnOneOfUMatrix = { 3, 0, 0, 0 };
            double[] columnTwoOfUMatrix = { 7, 8, 0, 0 };
            double[] columnThreeOfUMatrix = { 2, 4, 9, 0 };
            double[] columnFourOfUMatrix = { 5, 2, 3, 1 };

            correctUPartOfLUPDecomposition.SetColumn(0, columnOneOfUMatrix);
            correctUPartOfLUPDecomposition.SetColumn(1, columnTwoOfUMatrix);
            correctUPartOfLUPDecomposition.SetColumn(2, columnThreeOfUMatrix);
            correctUPartOfLUPDecomposition.SetColumn(3, columnFourOfUMatrix);

            //Calculate U Part
            Matrix calculatedUPartOfLUPDecomposition = matrixA.ExtractUpper();

            (calculatedUPartOfLUPDecomposition == correctUPartOfLUPDecomposition).Should().BeTrue();

        }