Stricter rules on pytest.raises, requiring match for generic error types

Closes #560

pyproject.toml

@@ -136,8 +136,6 @@ ignore = [
     "PLR2004", # Ignore magic values in comparison for now. It doesn't seem we can set
                # allowed magic values and a number of our magic values are not really
                # magic (such as 255 when doing uint8 maths)
-    "PT011", # Ignore pytest.raises being used on too general expectations without a
-             # match. We may need to revisit this.
     "SIM105", # Not enforcing use of `contextlib.suppress(NotConnectedToServerError)`
               # instead of `try`-`except`-`pass`
 ]

tests/test_scan_planners.py

@@ -15,7 +15,7 @@ def test_enforce_xy_tuple():
     """Check that 2 value tuples (or ValueErrors) are always returned."""
     bad_len_vals = [[1], [], (1,), (2, 4, 4), [1, 4, 5, 7]]
     for value in bad_len_vals:
-        with pytest.raises(ValueError):
+        with pytest.raises(ValueError, match="2 value tuple expected"):
             scan_planners.enforce_xy_tuple(value)
 
     bad_type_vals = ["hi", 1, {"this": "that"}, {1, 2}]
@@ -31,7 +31,7 @@ def test_enforce_xyz_tuple():
     """Check that 3 value tuples (or ValueErrors) are always returned."""
     bad_len_vals = [[1], [], (1,), (2, 4), [1, 4, 5, 7]]
     for value in bad_len_vals:
-        with pytest.raises(ValueError):
+        with pytest.raises(ValueError, match="3 value tuple expected"):
             scan_planners.enforce_xyz_tuple(value)
 
     bad_type_vals = ["hi!", 1, {"this": "that"}, {1, 2, 3}]
@@ -66,7 +66,7 @@ def test_v_basic_smart_spiral():
     assert z_pos is None
 
     # Try to mark location as imaged with only xy_position
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match="3 value tuple expected"):
         planner.mark_location_visited(xy_pos, imaged=False, focused=False)
     # scan still not complete
     assert not planner.scan_complete
@@ -87,7 +87,8 @@ def test_bad_smart_spiral_settings():
     initial_position = (100, 50)
 
     # Class init should raise error if no planner_settings dictionary set
-    with pytest.raises(ValueError):
+    msg = "SmartSpiral requires a planner_settings dictionary with keys"
+    with pytest.raises(ValueError, match=msg):
         scan_planners.SmartSpiral(initial_position=initial_position)
 
     planner_settings = {"dx": 50, "dy": 50, "max_dist": 10000}
@@ -108,7 +109,7 @@ def test_bad_smart_spiral_settings():
     for badkey in keys:
         bad_planner_settings = copy(planner_settings)
         bad_planner_settings[badkey] = "I can't be converted to an int"
-        with pytest.raises(ValueError):
+        with pytest.raises(ValueError, match="invalid literal for int()"):
             scan_planners.SmartSpiral(
                 initial_position=initial_position, planner_settings=bad_planner_settings
             )

tests/test_stack.py

@@ -86,7 +86,12 @@ def test_stack_params_not_enough_test_images(save_ims, extra_ims):
 
     For arguments see test_stack_params_validation
     """
-    with pytest.raises(ValueError):
+    # Depending on the values multiple messages are possible
+    match = (
+        "(Can't test for focus with fewer than 3 images|"
+        "Can't save more images than the minimum number tested)"
+    )
+    with pytest.raises(ValueError, match=match):
         StackParams(
             stack_dz=50,
             images_to_save=save_ims,
@@ -106,7 +111,12 @@ def test_stack_params_negative_images_to_save(save_ims, extra_ims):
 
     For arguments see test_stack_params_validation
     """
-    with pytest.raises(ValueError):
+    # Depending on the values multiple messages are possible
+    match = (
+        "(Can't test for focus with fewer than 3 images|"
+        "Images to save must be positive and odd)"
+    )
+    with pytest.raises(ValueError, match=match):
         StackParams(
             stack_dz=50,
             images_to_save=save_ims,
@@ -126,7 +136,13 @@ def test_even_min_images_to_test(save_ims, extra_ims):
 
     For arguments see test_stack_params_validation
     """
-    with pytest.raises(ValueError):
+    # Depending on the values multiple messages are possible
+    match = (
+        "(Can't test for focus with fewer than 3 images|"
+        "Testing with more than 9 images is|"  # may give more than 9 which errors first
+        "Minimum number of images to test should be positive and odd)"
+    )
+    with pytest.raises(ValueError, match=match):
         StackParams(
             stack_dz=50,
             images_to_save=save_ims,
@@ -146,7 +162,11 @@ def test_even_images_to_save(save_ims, extra_ims):
 
     For arguments see test_stack_params_validation
     """
-    with pytest.raises(ValueError):
+    match = (
+        "(Can't test for focus with fewer than 3 images|"
+        "Images to save must be positive and odd)"
+    )
+    with pytest.raises(ValueError, match=match):
         StackParams(
             stack_dz=50,
             images_to_save=save_ims,
@@ -232,13 +252,13 @@ def test_retrieval_of_captures(start):
         assert _get_capture_by_id(captures, buffer_id) is capture
 
     # Check errors are raised when supplying ids that aren't in the list
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match="No capture has a buffer id of"):
         _get_capture_index_by_id(captures, start - 1)
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match="No capture has a buffer id of"):
         _get_capture_index_by_id(captures, start + 21)
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match="No capture has a buffer id of"):
         _get_capture_by_id(captures, start - 1)
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match="No capture has a buffer id of"):
         _get_capture_by_id(captures, start + 21)