Merge pull request #3306 from nicoddemus/2405-scope-fixture-order

Instantiate fixtures by scope order in test function requests

_pytest/fixtures.py

@@ -1021,9 +1021,6 @@ class FixtureManager(object):
                     if nextchar and nextchar not in ":/":
                         continue
                 autousenames.extend(basenames)
-        # make sure autousenames are sorted by scope, scopenum 0 is session
-        autousenames.sort(
-            key=lambda x: self._arg2fixturedefs[x][-1].scopenum)
         return autousenames
 
     def getfixtureclosure(self, fixturenames, parentnode):
@@ -1054,6 +1051,16 @@ class FixtureManager(object):
                 if fixturedefs:
                     arg2fixturedefs[argname] = fixturedefs
                     merge(fixturedefs[-1].argnames)
+
+        def sort_by_scope(arg_name):
+            try:
+                fixturedefs = arg2fixturedefs[arg_name]
+            except KeyError:
+                return scopes.index('function')
+            else:
+                return fixturedefs[-1].scopenum
+
+        fixturenames_closure.sort(key=sort_by_scope)
         return fixturenames_closure, arg2fixturedefs
 
     def pytest_generate_tests(self, metafunc):

changelog/2405.feature.rst

@@ -0,0 +1 @@
+Fixtures are now instantiated based on their scopes, with higher-scoped fixtures (such as ``session``) being instantiated first than lower-scoped fixtures (such as ``function``). The relative order of fixtures of the same scope is kept unchanged, based in their declaration order and their dependencies.

doc/en/fixture.rst

@@ -256,6 +256,50 @@ instance, you can simply declare it:
 
 Finally, the ``class`` scope will invoke the fixture once per test *class*.
 
+
+Higher-scoped fixtures are instantiated first
+---------------------------------------------
+
+.. versionadded:: 3.5
+
+Within a function request for features, fixture of higher-scopes (such as ``session``) are instantiated first than
+lower-scoped fixtures (such as ``function`` or ``class``). The relative order of fixtures of same scope follows
+the declared order in the test function and honours dependencies between fixtures.
+
+Consider the code below:
+
+.. code-block:: python
+
+    @pytest.fixture(scope="session")
+    def s1():
+        pass
+
+    @pytest.fixture(scope="module")
+    def m1():
+        pass
+
+    @pytest.fixture
+    def f1(tmpdir):
+        pass
+
+    @pytest.fixture
+    def f2():
+        pass
+
+    def test_foo(f1, m1, f2, s1):
+        ...
+
+
+The fixtures requested by ``test_foo`` will be instantiated in the following order:
+
+1. ``s1``: is the highest-scoped fixture (``session``).
+2. ``m1``: is the second highest-scoped fixture (``module``).
+3. ``tempdir``: is a ``function``-scoped fixture, required by ``f1``: it needs to be instantiated at this point
+   because it is a dependency of ``f1``.
+4. ``f1``: is the first ``function``-scoped fixture in ``test_foo`` parameter list.
+5. ``f2``: is the last ``function``-scoped fixture in ``test_foo`` parameter list.
+
+
 .. _`finalization`:
 
 Fixture finalization / executing teardown code

testing/acceptance_test.py

@@ -964,3 +964,27 @@ def test_fixture_values_leak(testdir):
     """)
     result = testdir.runpytest()
     result.stdout.fnmatch_lines(['* 2 passed *'])
+
+
+def test_fixture_order_respects_scope(testdir):
+    """Ensure that fixtures are created according to scope order, regression test for #2405
+    """
+    testdir.makepyfile('''
+        import pytest
+
+        data = {}
+
+        @pytest.fixture(scope='module')
+        def clean_data():
+            data.clear()
+
+        @pytest.fixture(autouse=True)
+        def add_data():
+            data.update(value=True)
+
+        @pytest.mark.usefixtures('clean_data')
+        def test_value():
+            assert data.get('value')
+    ''')
+    result = testdir.runpytest()
+    assert result.ret == 0

testing/python/fixture.py

@@ -3,7 +3,7 @@ from textwrap import dedent
 import _pytest._code
 import pytest
 from _pytest.pytester import get_public_names
-from _pytest.fixtures import FixtureLookupError
+from _pytest.fixtures import FixtureLookupError, FixtureRequest
 from _pytest import fixtures
 
 
@@ -2281,19 +2281,19 @@ class TestFixtureMarker(object):
                     pass
         """)
         result = testdir.runpytest("-vs")
-        result.stdout.fnmatch_lines("""
+        result.stdout.re_match_lines(r"""
-            test_class_ordering.py::TestClass2::test_1[1-a] PASSED
+            test_class_ordering.py::TestClass2::test_1\[a-1\] PASSED
-            test_class_ordering.py::TestClass2::test_1[2-a] PASSED
+            test_class_ordering.py::TestClass2::test_1\[a-2\] PASSED
-            test_class_ordering.py::TestClass2::test_2[1-a] PASSED
+            test_class_ordering.py::TestClass2::test_2\[a-1\] PASSED
-            test_class_ordering.py::TestClass2::test_2[2-a] PASSED
+            test_class_ordering.py::TestClass2::test_2\[a-2\] PASSED
-            test_class_ordering.py::TestClass2::test_1[1-b] PASSED
+            test_class_ordering.py::TestClass2::test_1\[b-1\] PASSED
-            test_class_ordering.py::TestClass2::test_1[2-b] PASSED
+            test_class_ordering.py::TestClass2::test_1\[b-2\] PASSED
-            test_class_ordering.py::TestClass2::test_2[1-b] PASSED
+            test_class_ordering.py::TestClass2::test_2\[b-1\] PASSED
-            test_class_ordering.py::TestClass2::test_2[2-b] PASSED
+            test_class_ordering.py::TestClass2::test_2\[b-2\] PASSED
-            test_class_ordering.py::TestClass::test_3[1-a] PASSED
+            test_class_ordering.py::TestClass::test_3\[a-1\] PASSED
-            test_class_ordering.py::TestClass::test_3[2-a] PASSED
+            test_class_ordering.py::TestClass::test_3\[a-2\] PASSED
-            test_class_ordering.py::TestClass::test_3[1-b] PASSED
+            test_class_ordering.py::TestClass::test_3\[b-1\] PASSED
-            test_class_ordering.py::TestClass::test_3[2-b] PASSED
+            test_class_ordering.py::TestClass::test_3\[b-2\] PASSED
         """)
 
     def test_parametrize_separated_order_higher_scope_first(self, testdir):
@@ -3245,3 +3245,188 @@ def test_pytest_fixture_setup_and_post_finalizer_hook(testdir):
         "*TESTS finalizer hook called for my_fixture from test_func*",
         "*ROOT finalizer hook called for my_fixture from test_func*",
     ])
+
+
+class TestScopeOrdering(object):
+    """Class of tests that ensure fixtures are ordered based on their scopes (#2405)"""
+
+    @pytest.mark.parametrize('use_mark', [True, False])
+    def test_func_closure_module_auto(self, testdir, use_mark):
+        """Semantically identical to the example posted in #2405 when ``use_mark=True``"""
+        testdir.makepyfile("""
+            import pytest
+
+            @pytest.fixture(scope='module', autouse={autouse})
+            def m1(): pass
+
+            if {use_mark}:
+                pytestmark = pytest.mark.usefixtures('m1')
+
+            @pytest.fixture(scope='function', autouse=True)
+            def f1(): pass
+
+            def test_func(m1):
+                pass
+        """.format(autouse=not use_mark, use_mark=use_mark))
+        items, _ = testdir.inline_genitems()
+        request = FixtureRequest(items[0])
+        assert request.fixturenames == 'm1 f1'.split()
+
+    def test_func_closure_with_native_fixtures(self, testdir, monkeypatch):
+        """Sanity check that verifies the order returned by the closures and the actual fixture execution order:
+        The execution order may differ because of fixture inter-dependencies.
+        """
+        monkeypatch.setattr(pytest, 'FIXTURE_ORDER', [], raising=False)
+        testdir.makepyfile("""
+            import pytest
+
+            FIXTURE_ORDER = pytest.FIXTURE_ORDER
+
+            @pytest.fixture(scope="session")
+            def s1():
+                FIXTURE_ORDER.append('s1')
+
+            @pytest.fixture(scope="module")
+            def m1():
+                FIXTURE_ORDER.append('m1')
+
+            @pytest.fixture(scope='session')
+            def my_tmpdir_factory():
+                FIXTURE_ORDER.append('my_tmpdir_factory')
+
+            @pytest.fixture
+            def my_tmpdir(my_tmpdir_factory):
+                FIXTURE_ORDER.append('my_tmpdir')
+
+            @pytest.fixture
+            def f1(my_tmpdir):
+                FIXTURE_ORDER.append('f1')
+
+            @pytest.fixture
+            def f2():
+                FIXTURE_ORDER.append('f2')
+
+            def test_foo(f1, m1, f2, s1): pass
+        """)
+        items, _ = testdir.inline_genitems()
+        request = FixtureRequest(items[0])
+        # order of fixtures based on their scope and position in the parameter list
+        assert request.fixturenames == 's1 my_tmpdir_factory m1 f1 f2 my_tmpdir'.split()
+        testdir.runpytest()
+        # actual fixture execution differs: dependent fixtures must be created first ("my_tmpdir")
+        assert pytest.FIXTURE_ORDER == 's1 my_tmpdir_factory m1 my_tmpdir f1 f2'.split()
+
+    def test_func_closure_module(self, testdir):
+        testdir.makepyfile("""
+            import pytest
+
+            @pytest.fixture(scope='module')
+            def m1(): pass
+
+            @pytest.fixture(scope='function')
+            def f1(): pass
+
+            def test_func(f1, m1):
+                pass
+        """)
+        items, _ = testdir.inline_genitems()
+        request = FixtureRequest(items[0])
+        assert request.fixturenames == 'm1 f1'.split()
+
+    def test_func_closure_scopes_reordered(self, testdir):
+        """Test ensures that fixtures are ordered by scope regardless of the order of the parameters, although
+        fixtures of same scope keep the declared order
+        """
+        testdir.makepyfile("""
+            import pytest
+
+            @pytest.fixture(scope='session')
+            def s1(): pass
+
+            @pytest.fixture(scope='module')
+            def m1(): pass
+
+            @pytest.fixture(scope='function')
+            def f1(): pass
+
+            @pytest.fixture(scope='function')
+            def f2(): pass
+
+            class Test:
+
+                @pytest.fixture(scope='class')
+                def c1(cls): pass
+
+                def test_func(self, f2, f1, c1, m1, s1):
+                    pass
+        """)
+        items, _ = testdir.inline_genitems()
+        request = FixtureRequest(items[0])
+        assert request.fixturenames == 's1 m1 c1 f2 f1'.split()
+
+    def test_func_closure_same_scope_closer_root_first(self, testdir):
+        """Auto-use fixtures of same scope are ordered by closer-to-root first"""
+        testdir.makeconftest("""
+            import pytest
+
+            @pytest.fixture(scope='module', autouse=True)
+            def m_conf(): pass
+        """)
+        testdir.makepyfile(**{
+            'sub/conftest.py': """
+                import pytest
+
+                @pytest.fixture(scope='module', autouse=True)
+                def m_sub(): pass
+            """,
+            'sub/test_func.py': """
+                import pytest
+
+                @pytest.fixture(scope='module', autouse=True)
+                def m_test(): pass
+
+                @pytest.fixture(scope='function')
+                def f1(): pass
+
+                def test_func(m_test, f1):
+                    pass
+        """})
+        items, _ = testdir.inline_genitems()
+        request = FixtureRequest(items[0])
+        assert request.fixturenames == 'm_conf m_sub m_test f1'.split()
+
+    def test_func_closure_all_scopes_complex(self, testdir):
+        """Complex test involving all scopes and mixing autouse with normal fixtures"""
+        testdir.makeconftest("""
+            import pytest
+
+            @pytest.fixture(scope='session')
+            def s1(): pass
+        """)
+        testdir.makepyfile("""
+            import pytest
+
+            @pytest.fixture(scope='module', autouse=True)
+            def m1(): pass
+
+            @pytest.fixture(scope='module')
+            def m2(s1): pass
+
+            @pytest.fixture(scope='function')
+            def f1(): pass
+
+            @pytest.fixture(scope='function')
+            def f2(): pass
+
+            class Test:
+
+                @pytest.fixture(scope='class', autouse=True)
+                def c1(self):
+                    pass
+
+                def test_func(self, f2, f1, m2):
+                    pass
+        """)
+        items, _ = testdir.inline_genitems()
+        request = FixtureRequest(items[0])
+        assert request.fixturenames == 's1 m1 m2 c1 f2 f1'.split()