fx, xy unit tests added to higher.

add --run-slow flag for pytest in conftest.py

run --run-slow in pre-commit

call tests.command.reset() before each test run

tests/conftest.py

@@ -0,0 +1,7 @@
+def pytest_addoption(parser):
+    parser.addoption(
+        "--run-slow",
+        action="store_true",
+        default=False,
+        help="Run slow tests",
+    )