def test_q_matrix(self):
a, b, c, d = randomElements()
q = Quaternion(a, b, c, d)
M = np.array([
[a, -b, -c, -d],
[b, a, -d, c],
[c, d, a, -b],
[d, -c, b, a]])
self.assertTrue(np.array_equal(q._q_matrix(), M))
