def test_merge_simple_trackers():
x1 = VarianceTracker()
x1.update(1.0)
x2 = VarianceTracker()
x2.update(2.0)
x2.update(3.0)
merged = x1.merge(x2)
assert merged.mean == pytest.approx(2.0, 1e-4)
assert merged.variance() == pytest.approx(1.0, 1e-4)
assert merged.count == 3
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_merge_with_empty_tracker():
x1 = VarianceTracker()
vals = list(range(10))
for v in vals:
x1.update(v)
var = x1.variance()
mean = x1.mean
count = x1.count
x2 = x1.merge(VarianceTracker())
assert var == x2.variance()
assert mean == x2.mean
assert count == x2.count
assert x1.variance() == x2.variance()
assert x1.mean == x2.mean
assert x1.count == x2.count