[Tests] Add Specification tests

Asserts they contain a single usage trait. This is required for runtime
introspection of the puropse of the spec.

Asserts Specification traits constructible, as we were implicitly
testing this as part of checking the trait set contained a usage trait
(as the traitgen uses their attr to build the set), but that was relying
on an implementation details. This requires that MediaCreation
doesn't reference any other packages (which it doesn't at present).

Asserts relationship specication names follow guidelines.

Signed-off-by: Tom Cowland <[email protected]>

Author: foundrytom

tests/python/openassetio_mediacreation/test_specifications.py

@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: Apache-2.0
+# Copyright 2023 The Foundry Visionmongers Ltd
+"""
+Tests Specifications include required traits.
+"""
+
+# pylint: disable=no-self-use
+# pylint: disable=invalid-name
+# pylint: disable=missing-class-docstring
+
+import inspect
+
+import pytest
+
+from openassetio_mediacreation.traits.usage import EntityTrait, RelationshipTrait
+from openassetio_mediacreation import specifications
+
+
+class Test_specification_traits:
+    def test_contain_usage_trait(self):
+        """
+        All specifications should contain one trait from the usage namespace
+        so that their purpose can be determined at runtime.
+        """
+        for cls in self.__specifications():
+            # Ensure exactly one is present
+            assert (EntityTrait.kId in cls.kTraitSet) != (RelationshipTrait.kId in cls.kTraitSet)
+
+    def test_traits_constructible(self):
+        """
+        Asserts that specifications reference valid traits, without
+        relying on private knowledge that the trait set already uses
+        their Id attribute.
+        """
+        for cls in self.__specifications():
+            instance = cls.create()
+            functions = inspect.getmembers(instance, inspect.ismethod)
+            for _, func in functions:
+                if not func.__name__.endswith("Trait"):
+                    continue
+                func()
+
+    def test_relationship_names_suffixed(self):
+        """
+        Relationship specifications should be suffixed with "Relationship"
+        """
+        for cls in self.__specifications():
+            if RelationshipTrait.kId in cls.kTraitSet:
+                assert cls.__name__.endswith("RelationshipSpecification")
+
+    def __specifications(self):
+        """
+        Retrieves all defined Specification classes
+        """
+        specs = []
+        namespaces = inspect.getmembers(specifications, inspect.ismodule)
+        for _, namespace in namespaces:
+            classes = inspect.getmembers(namespace, inspect.isclass)
+            for _, cls in classes:
+                if cls.__name__.endswith("Specification"):
+                    specs.append(cls)
+        assert specs
+        return specs