def test_merge_bigger():
x1 = VarianceTracker()
for i in range(10):
x1.update(i)
assert x1.variance() == pytest.approx(9.1667, 1e-4)
assert x1.count == 10
assert x1.mean == pytest.approx(4.5, 1e-7)
merged = x1.merge(x1.copy())
assert merged.variance() == pytest.approx(8.684, 1e-4)
assert merged.count == 20
assert merged.mean == pytest.approx(4.5, 1e-7)
def test_copy():
x1 = VarianceTracker()
for i in range(10):
x1.update(i)
var = x1.variance()
count = x1.count
mean = x1.mean
x2 = x1.copy()
assert x2.variance() == var
assert x2.count == count
assert x2.mean == mean
for i in range(3):
x1.update(i)
assert x1.variance() != var
assert x1.count == count + 3
assert x1.mean != mean
assert x2.variance() == var
assert x2.mean == mean
assert x2.count == count