@Test
public void testSimpleHash() {

  // Just a simple sanity check.
  final Matrix3 mat1 = new Matrix3(1, 2, 3, 4, 5, 6, 7, 8, 9);
  final Matrix3 mat2 = new Matrix3(1, 2, 3, 4, 5, 6, 7, 8, 9);
  final Matrix3 mat3 = new Matrix3(1, 2, 3, 4, 5, 6, 7, 8, 0);
  assertTrue(mat1.hashCode() == mat2.hashCode());
  assertTrue(mat1.hashCode() != mat3.hashCode());
}