Add strict QT mode to tests

Author: dstansby

src/napari_matplotlib/tests/conftest.py

@@ -1,3 +1,5 @@
+import os
+
 import numpy as np
 import pytest
 from skimage import data
@@ -22,3 +24,17 @@ def astronaut_data():
 @pytest.fixture
 def brain_data():
     return data.brain(), {"rgb": False}
+
+
+@pytest.fixture(autouse=True, scope="session")
+def set_strict_qt():
+    env_var = "NAPARI_STRICT_QT"
+    old_val = os.environ.get(env_var)
+    os.environ[env_var] = "1"
+    # Run tests
+    yield
+    # Reset to original value
+    if old_val is not None:
+        os.environ[env_var] = old_val
+    else:
+        del os.environ[env_var]