What are the two matrices rot_test_y and rot_test_z in the RobotArm.cpp file used for?

[captain316]

rot_test_y[0][0] = cos(DEGRE2RAD(-90));  
rot_test_y[0][2] = sin(DEGRE2RAD(-90));
rot_test_y[2][0] = -sin(DEGRE2RAD(-90));
rot_test_y[2][2] = cos(DEGRE2RAD(-90));	

rot_test_z[0][0] = cos(DEGRE2RAD(180));
rot_test_z[0][1] = -sin(DEGRE2RAD(180));
rot_test_z[1][0] = sin(DEGRE2RAD(180));
rot_test_z[1][1] = cos(DEGRE2RAD(180));

    MatrixCalc::MatrixMull(move,rot_test_y,mid_matrix_1);      	 
MatrixCalc::MatrixMull(mid_matrix_1,rot_test_z,mid_matrix_2);
MatrixCalc::MatrixMull(mid_matrix_2,rot_x,mid_matrix_1);

MatrixCalc::MatrixMull(mid_matrix_1,rot_y,mid_matrix_2);
MatrixCalc::MatrixMull(mid_matrix_2,rot_z,mid_matrix_1);

What role do they play in subsequent matrix transformations?