Use pytest.raises() instead of try..except in tests (pydantic#12228)

Co-authored-by: Dani Pinyol <[email protected]>

Author: dpinol

tests/test_dataclasses.py

@@ -3145,21 +3145,17 @@ class MyDataclass:
 
     inst = MyDataclass('hello')
 
-    try:
+    with pytest.raises(dataclasses.FrozenInstanceError, match="cannot assign to field 'x'"):
         inst.x = 'other'
-    except Exception as e:
-        assert "cannot assign to field 'x'" in repr(e)
 
     @pydantic.dataclasses.dataclass(config=ConfigDict(frozen=True))
     class MyDataclass2:
         x: str
 
     inst = MyDataclass2('hello')
 
-    try:
+    with pytest.raises(dataclasses.FrozenInstanceError, match="cannot assign to field 'x'"):
         inst.x = 'other'
-    except Exception as e:
-        assert "cannot assign to field 'x'" in repr(e)
 
 
 def test_frozen_with_validate_assignment() -> None:

tests/test_discriminated_union.py

@@ -1772,35 +1772,35 @@ def model_x_discriminator(v):
         if isinstance(v, (dict, BaseModel)):
             return 'model'
 
-    try:
+    with pytest.raises(PydanticUserError) as exc_info:
 
         class DiscriminatedModel(BaseModel):
             x: Annotated[
                 Union[str, 'DiscriminatedModel'],
                 Discriminator(model_x_discriminator),
             ]
-    except PydanticUserError as exc_info:
-        assert exc_info.code == 'callable-discriminator-no-tag'
 
-    try:
+    assert exc_info.value.code == 'callable-discriminator-no-tag'
+
+    with pytest.raises(PydanticUserError) as exc_info:
 
         class DiscriminatedModel(BaseModel):
             x: Annotated[
                 Union[Annotated[str, Tag('str')], 'DiscriminatedModel'],
                 Discriminator(model_x_discriminator),
             ]
-    except PydanticUserError as exc_info:
-        assert exc_info.code == 'callable-discriminator-no-tag'
 
-    try:
+    assert exc_info.value.code == 'callable-discriminator-no-tag'
+
+    with pytest.raises(PydanticUserError) as exc_info:
 
         class DiscriminatedModel(BaseModel):
             x: Annotated[
                 Union[str, Annotated['DiscriminatedModel', Tag('model')]],
                 Discriminator(model_x_discriminator),
             ]
-    except PydanticUserError as exc_info:
-        assert exc_info.code == 'callable-discriminator-no-tag'
+
+    assert exc_info.value.code == 'callable-discriminator-no-tag'
 
 
 @pytest.mark.xfail(