def test_statistic_moment_evaluation():
st = Statistic([1])
assert st.moment(1) == 1
assert st.moment(2) == 1
st.extend([2, 3, 4])
assert st.moment(1) == 2.5
assert st.moment(2) == 7.5
def test_statistic_moment_raises_error_when_passed_zero_negative_or_float():
st = Statistic([1, 2, 3])
with pytest.raises(ValueError) as excinfo:
st.moment(0)
assert 'positive integer expected' in str(excinfo.value).lower()
with pytest.raises(ValueError) as excinfo:
st.moment(-1)
assert 'positive integer expected' in str(excinfo.value).lower()
with pytest.raises(ValueError) as excinfo:
st.moment(1.5)
assert 'positive integer expected' in str(excinfo.value).lower()
def test_statistic_moment_raises_error_when_called_for_empty_statistic():
st = Statistic()
with pytest.raises(ValueError) as excinfo:
st.moment(1)
assert 'no data' in str(excinfo.value).lower()