@Test public void shouldRotateMatrix() {

  int[][] matrix = { { 0, 1, 2 }, { 3, 4, 5 }, { 6, 7, 8 } };
  rotateMatrix.rotate(matrix);
  int[][] expectedResult = { { 6, 3, 0 }, { 7, 4, 1 }, { 8, 5, 2 } };
  assertArrayEquals(expectedResult, matrix);
}