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Backport PR #16940 on branch v3.2.x (DOC/FIX: clarify the docs for check_figures_equal) #16974

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Merged
merged 1 commit into from
Mar 31, 2020
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Merged

Backport PR #16940 on branch v3.2.x (DOC/FIX: clarify the docs for check_figures_equal) #16974

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12 changes: 9 additions & 3 deletions lib/matplotlib/testing/decorators.py
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Original file line number Diff line number Diff line change
Expand Up @@ -358,9 +358,9 @@ def check_figures_equal(*, extensions=("png", "pdf", "svg"), tol=0):
"""
Decorator for test cases that generate and compare two figures.

The decorated function must take two arguments, *fig_test* and *fig_ref*,
and draw the test and reference images on them. After the function
returns, the figures are saved and compared.
The decorated function must take two keyword arguments, *fig_test*
and *fig_ref*, and draw the test and reference images on them.
After the function returns, the figures are saved and compared.

This decorator should be preferred over `image_comparison` when possible in
order to keep the size of the test suite from ballooning.
Expand All @@ -381,6 +381,7 @@ def check_figures_equal(*, extensions=("png", "pdf", "svg"), tol=0):
def test_plot(fig_test, fig_ref):
fig_test.subplots().plot([1, 3, 5])
fig_ref.subplots().plot([0, 1, 2], [1, 3, 5])

"""
ALLOWED_CHARS = set(string.digits + string.ascii_letters + '_-[]()')
KEYWORD_ONLY = inspect.Parameter.KEYWORD_ONLY
Expand All @@ -390,6 +391,11 @@ def decorator(func):
_, result_dir = _image_directories(func)
old_sig = inspect.signature(func)

if not {"fig_test", "fig_ref"}.issubset(old_sig.parameters):
raise ValueError("The decorated function must have at least the "
"parameters 'fig_ref' and 'fig_test', but your "
f"function has the signature {old_sig}")

@pytest.mark.parametrize("ext", extensions)
def wrapper(*args, **kwargs):
ext = kwargs['ext']
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7 changes: 7 additions & 0 deletions lib/matplotlib/tests/test_testing.py
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Expand Up @@ -15,3 +15,10 @@ def test_warn_to_fail():
@pytest.mark.parametrize("b", [1])
def test_parametrize_with_check_figure_equal(a, fig_ref, b, fig_test):
assert a == b


def test_wrap_failure():
with pytest.raises(ValueError, match="^The decorated function"):
@check_figures_equal()
def should_fail(test, ref):
pass