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Merged
merged 3 commits into from
Dec 29, 2020
Merged

Check that no new figures are created in image comparison tests #19179

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9b5ecff
Check that no new figures are created in image comparison tests
dstansby Dec 27, 2020
5a33bcc
Fix acorr test
dstansby Dec 27, 2020
b1b6bea
Add tests
dstansby Dec 28, 2020
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16 changes: 16 additions & 0 deletions lib/matplotlib/testing/decorators.py
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Original file line number Diff line number Diff line change
Expand Up @@ -408,6 +408,12 @@ def check_figures_equal(*, extensions=("png", "pdf", "svg"), tol=0):
tol : float
The RMS threshold above which the test is considered failed.

Raises
------
RuntimeError
If any new figures are created (and not subsequently closed) inside
the test function.

Examples
--------
Check that calling `.Axes.plot` with a single argument plots it against
Expand All @@ -421,6 +427,7 @@ def test_plot(fig_test, fig_ref):
"""
ALLOWED_CHARS = set(string.digits + string.ascii_letters + '_-[]()')
KEYWORD_ONLY = inspect.Parameter.KEYWORD_ONLY

def decorator(func):
import pytest

Expand All @@ -444,7 +451,16 @@ def wrapper(*args, ext, request, **kwargs):
try:
fig_test = plt.figure("test")
fig_ref = plt.figure("reference")
# Keep track of number of open figures, to make sure test
# doesn't create any new ones
n_figs = len(plt.get_fignums())
func(*args, fig_test=fig_test, fig_ref=fig_ref, **kwargs)
if len(plt.get_fignums()) > n_figs:
raise RuntimeError('Number of open figures changed during '
'test. Make sure you are plotting to '
'fig_test or fig_ref, or if this is '
'deliberate explicitly close the '
'new figure(s) inside the test.')
test_image_path = result_dir / (file_name + "." + ext)
ref_image_path = result_dir / (file_name + "-expected." + ext)
fig_test.savefig(test_image_path)
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4 changes: 2 additions & 2 deletions lib/matplotlib/tests/test_axes.py
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Expand Up @@ -109,10 +109,10 @@ def test_acorr(fig_test, fig_ref):
x = np.random.normal(0, 1, Nx).cumsum()
maxlags = Nx-1

fig_test, ax_test = plt.subplots()
ax_test = fig_test.subplots()
ax_test.acorr(x, maxlags=maxlags)

fig_ref, ax_ref = plt.subplots()
ax_ref = fig_ref.subplots()
# Normalized autocorrelation
norm_auto_corr = np.correlate(x, x, mode="full")/np.dot(x, x)
lags = np.arange(-maxlags, maxlags+1)
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17 changes: 17 additions & 0 deletions lib/matplotlib/tests/test_testing.py
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@@ -1,5 +1,8 @@
import warnings

import pytest

import matplotlib.pyplot as plt
from matplotlib.testing.decorators import check_figures_equal


Expand All @@ -22,3 +25,17 @@ def test_wrap_failure():
@check_figures_equal()
def should_fail(test, ref):
pass


@pytest.mark.xfail(raises=RuntimeError, strict=True,
reason='Test for check_figures_equal test creating '
'new figures')
@check_figures_equal()
def test_check_figures_equal_extra_fig(fig_test, fig_ref):
plt.figure()


@check_figures_equal()
def test_check_figures_equal_closed_fig(fig_test, fig_ref):
fig = plt.figure()
plt.close(fig)