implement fixture isolation

isolate state changes inside fixtures

boa/test/plugin.py

@@ -1,4 +1,5 @@
 import contextlib
+import warnings
 from typing import Generator
 
 import hypothesis
@@ -50,6 +51,23 @@ def pytest_collection_modifyitems(config, items):
                 item.add_marker("gas_profile")
 
 
+_fixture_map = {}
+
+
+def pytest_fixture_setup(fixturedef, request):
+    ctx = boa.env.anchor()
+    assert id(fixturedef) not in _fixture_map, "bad invariant"
+    _fixture_map[id(fixturedef)] = ctx
+    ctx.__enter__()
+
+
+def pytest_fixture_post_finalizer(fixturedef, request):
+    if (ctx := _fixture_map.pop(id(fixturedef), None)) is not None:
+        ctx.__exit__(None, None, None)
+    else:
+        warnings.warn("possible bug in titanoboa! bad fixture tracking", stacklevel=1)
+
+
 @pytest.hookimpl(hookwrapper=True)
 def pytest_runtest_call(item: pytest.Item) -> Generator:
     ignore_isolation = item.get_closest_marker("ignore_isolation") is not None

tests/unitary/test_isolation.py

@@ -66,3 +66,16 @@ def setup_ignore_isolation(boa_contract):
 def test_check_ignore_isolation(boa_contract, setup_ignore_isolation):
     assert boa_contract.a() == 42069
     assert boa_contract.b() == addr_constn
+
+
+@pytest.fixture(scope="function")
+def modify_boa_contract(boa_contract):
+    # these values spill over from the previous test
+    assert boa_contract.a() == 42069
+    assert boa_contract.b() == addr_constn
+    boa_contract.set_vars(boa_contract.a() + 1, boa.env.generate_address())
+
+
+@pytest.mark.parametrize("a", range(10))
+def test_fixture_isolation(modify_boa_contract, a):
+    pass