test: cap matplotlib<3.11 to stabilize colorbar image baselines#713
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matplotlib 3.11.0 (released 2026-06-12) changes colorbar/image rasterization enough to push tests/pl/test_colorbar.py image comparisons past the RMS tolerance (RMS ~22-31 vs 15), failing CI repo-wide on the py3.11-stable env. Cap matplotlib in the 'test' dependency-group only; the runtime dependency stays open so users/downstream still get 3.11. Temporary until the colorbar baselines are regenerated against 3.11.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #713 +/- ##
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+ Coverage 76.26% 76.28% +0.02%
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Files 14 14
Lines 4327 4327
Branches 1006 1006
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+ Hits 3300 3301 +1
Misses 667 667
+ Partials 360 359 -1 🚀 New features to boost your workflow:
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Problem
matplotlib==3.11.0was released on 2026-06-12 (02:27 UTC) and changes colorbar/image rasterization enough to pushtests/pl/test_colorbar.py::TestColorbarControlsimage comparisons past the RMS tolerance (RMS ~22–31 vs tol 15). This fails CI repo-wide on thehatch-test.py3.11-stableenv —mainand every open PR will go red on their next run onceuvresolves 3.11.0. (py3.14-stableis unaffected for now: 3.11.0 ships no cp314 wheel yet, so that env stays on 3.10.x.)Confirmed via PyPI upload timestamp: the last passing run resolved 3.10.x (run before 3.11.0 existed), the first failing run resolved 3.11.0. No source change is involved.
Fix
Cap
matplotlib<3.11in thetestdependency-group only. CI'shatch-testenv installs that group, so the cap applies to testing; the package's runtimematplotlibdependency stays open, so users and downstream libraries still resolve 3.11.Follow-up
Temporary. The proper fix is to regenerate the
test_colorbarbaselines against matplotlib 3.11 and lift the cap; the inline comment flags that.