@Test
public void testSimpleHash() {

  // Just a simple sanity check.
  final Matrix4 mat1 = new Matrix4(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16);
  final Matrix4 mat2 = new Matrix4(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16);
  final Matrix4 mat3 = new Matrix4(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0);
  assertTrue(mat1.hashCode() == mat2.hashCode());
  assertTrue(mat1.hashCode() != mat3.hashCode());
}