def METHOD_NAME(self):
    a = np.random.randint(0, 10, size=5)
    b = np.random.randint(0, 10, size=10)
    var = parallel_variance(
        a.mean(), len(a), a.var(ddof=1), b.mean(), len(b), b.var(ddof=1))
    expected_var = np.concatenate((a, b)).var(ddof=1)
    self.assertAlmostEqual(var, expected_var)