Add _sys_snapshot fixture and use it with more tests

src/_pytest/pytester.py

@@ -335,6 +335,15 @@ def testdir(request, tmpdir_factory):
     return Testdir(request, tmpdir_factory)
 
 
+@pytest.fixture
+def _sys_snapshot():
+    snappaths = SysPathsSnapshot()
+    snapmods = SysModulesSnapshot()
+    yield
+    snapmods.restore()
+    snappaths.restore()
+
+
 @pytest.fixture
 def _config_for_test():
     from _pytest.config import get_config

testing/acceptance_test.py

@@ -485,7 +485,7 @@ class TestGeneralUsage(object):
             ["*source code not available*", "E*fixture 'invalid_fixture' not found"]
         )
 
-    def test_plugins_given_as_strings(self, tmpdir, monkeypatch):
+    def test_plugins_given_as_strings(self, tmpdir, monkeypatch, _sys_snapshot):
         """test that str values passed to main() as `plugins` arg
         are interpreted as module names to be imported and registered.
         #855.

testing/code/test_excinfo.py

@@ -441,7 +441,7 @@ def test_match_raises_error(testdir):
 
 class TestFormattedExcinfo(object):
     @pytest.fixture
-    def importasmod(self, request):
+    def importasmod(self, request, _sys_snapshot):
         def importasmod(source):
             source = textwrap.dedent(source)
             tmpdir = request.getfixturevalue("tmpdir")

testing/code/test_source.py

@@ -410,7 +410,7 @@ def test_deindent():
     assert lines == ["def f():", "    def g():", "        pass"]
 
 
-def test_source_of_class_at_eof_without_newline(tmpdir):
+def test_source_of_class_at_eof_without_newline(tmpdir, _sys_snapshot):
     # this test fails because the implicit inspect.getsource(A) below
     # does not return the "x = 1" last line.
     source = _pytest._code.Source(

testing/test_config.py

@@ -436,7 +436,7 @@ class TestConfigAPI(object):
 
 
 class TestConfigFromdictargs(object):
-    def test_basic_behavior(self):
+    def test_basic_behavior(self, _sys_snapshot):
         from _pytest.config import Config
 
         option_dict = {"verbose": 444, "foo": "bar", "capture": "no"}
@@ -450,7 +450,7 @@ class TestConfigFromdictargs(object):
         assert config.option.capture == "no"
         assert config.args == args
 
-    def test_origargs(self):
+    def test_origargs(self, _sys_snapshot):
         """Show that fromdictargs can handle args in their "orig" format"""
         from _pytest.config import Config
 
@@ -1057,7 +1057,7 @@ class TestOverrideIniArgs(object):
             assert rootdir == tmpdir
             assert inifile is None
 
-    def test_addopts_before_initini(self, monkeypatch, _config_for_test):
+    def test_addopts_before_initini(self, monkeypatch, _config_for_test, _sys_snapshot):
         cache_dir = ".custom_cache"
         monkeypatch.setenv("PYTEST_ADDOPTS", "-o cache_dir=%s" % cache_dir)
         config = _config_for_test
@@ -1092,7 +1092,7 @@ class TestOverrideIniArgs(object):
         )
         assert result.ret == _pytest.main.EXIT_USAGEERROR
 
-    def test_override_ini_does_not_contain_paths(self, _config_for_test):
+    def test_override_ini_does_not_contain_paths(self, _config_for_test, _sys_snapshot):
         """Check that -o no longer swallows all options after it (#3103)"""
         config = _config_for_test
         config._preparse(["-o", "cache_dir=/cache", "/some/test/path"])

testing/test_conftest.py

@@ -11,8 +11,6 @@ from _pytest.config import PytestPluginManager
 from _pytest.main import EXIT_NOTESTSCOLLECTED
 from _pytest.main import EXIT_OK
 from _pytest.main import EXIT_USAGEERROR
-from _pytest.pytester import SysModulesSnapshot
-from _pytest.pytester import SysPathsSnapshot
 
 
 def ConftestWithSetinitial(path):
@@ -32,6 +30,7 @@ def conftest_setinitial(conftest, args, confcutdir=None):
     conftest._set_initial_conftests(Namespace())
 
 
+@pytest.mark.usefixtures("_sys_snapshot")
 class TestConftestValueAccessGlobal(object):
     @pytest.fixture(scope="module", params=["global", "inpackage"])
     def basedir(self, request, tmpdir_factory):
@@ -44,15 +43,6 @@ class TestConftestValueAccessGlobal(object):
 
         yield tmpdir
 
-    @pytest.fixture(autouse=True)
-    def restore(self):
-        """Restore sys.modules to prevent ConftestImportFailure when run randomly."""
-        snapmods = SysModulesSnapshot()
-        snappath = SysPathsSnapshot()
-        yield
-        snapmods.restore()
-        snappath.restore()
-
     def test_basic_init(self, basedir):
         conftest = PytestPluginManager()
         p = basedir.join("adir")
@@ -91,7 +81,7 @@ class TestConftestValueAccessGlobal(object):
         assert path.purebasename.startswith("conftest")
 
 
-def test_conftest_in_nonpkg_with_init(tmpdir):
+def test_conftest_in_nonpkg_with_init(tmpdir, _sys_snapshot):
     tmpdir.ensure("adir-1.0/conftest.py").write("a=1 ; Directory = 3")
     tmpdir.ensure("adir-1.0/b/conftest.py").write("b=2 ; a = 1.5")
     tmpdir.ensure("adir-1.0/b/__init__.py")