Python: Add tests for pytest fixture unused import FPs

Author: tausbn

python/ql/test/query-tests/Imports/unused/UnusedImport.expected

@@ -5,3 +5,6 @@
 | imports_test.py:10:1:10:22 | Import | Import of 'top_level_cycle' is not used. |
 | imports_test.py:27:1:27:25 | Import | Import of 'func2' is not used. |
 | imports_test.py:34:1:34:14 | Import | Import of 'module2' is not used. |
+| imports_test.py:116:1:116:67 | Import | Import of 'fixture' is not used. |
+| imports_test.py:116:1:116:67 | Import | Import of 'not_a_fixture' is not used. |
+| imports_test.py:116:1:116:67 | Import | Import of 'wrapped_fixture' is not used. |

python/ql/test/query-tests/Imports/unused/imports_test.py

@@ -111,3 +111,6 @@ def bar(x: Optional['subexpression_parameter_annotation']):
 
 def baz() -> Optional['subexpression_return_type']:
     pass
+
+
+from pytest_fixtures import fixture, wrapped_fixture, not_a_fixture

python/ql/test/query-tests/Imports/unused/pytest_fixtures.py

@@ -0,0 +1,19 @@
+import pytest
+
+
+@pytest.fixture
+def fixture():
+    pass
+
+def fixture_wrapper():
+    @pytest.fixture
+    def delegate():
+        pass
+    return delegate
+
+@fixture_wrapper
+def wrapped_fixture():
+    pass
+
+def not_a_fixture():
+    pass