From 486353c70ce3bc2ce8a77619c6b6cbdc5b2d91cf Mon Sep 17 00:00:00 2001
From: Daniel Hahler <git@thequod.de>
Date: Fri, 3 Apr 2020 07:19:33 +0200
Subject: [PATCH 1/2] Fix tests: use explicit syspathinsert

Use `testdir.syspathinsert()` with multiprocessing tests:

- `test_chained_exceptions_no_reprcrash`
- `test_exception_handling_no_traceback`

This only works currently because `_importtestmodule` changes `sys.path`
as a side-effect.

It appears to be only required on Windows though - likely due to the
multiprocessing method used there.
---
 testing/test_assertion.py | 1 +
 testing/test_reports.py   | 1 +
 2 files changed, 2 insertions(+)

diff --git a/testing/test_assertion.py b/testing/test_assertion.py
index 3d8fa912272..c97da3a024f 100644
--- a/testing/test_assertion.py
+++ b/testing/test_assertion.py
@@ -1409,6 +1409,7 @@ def test_multitask_job():
             multitask_job()
     """
     )
+    testdir.syspathinsert()
     result = testdir.runpytest(p1, "--tb=long")
     result.stdout.fnmatch_lines(
         [
diff --git a/testing/test_reports.py b/testing/test_reports.py
index 8c509ec479d..13f5932156b 100644
--- a/testing/test_reports.py
+++ b/testing/test_reports.py
@@ -362,6 +362,7 @@ def test_a():
             """
             )
 
+        testdir.syspathinsert()
         reprec = testdir.inline_run()
 
         reports = reprec.getreports("pytest_runtest_logreport")

From 9b06f36a574b27dabf5528b9ecf11b38ec05ba6b Mon Sep 17 00:00:00 2001
From: Daniel Hahler <git@thequod.de>
Date: Thu, 2 Apr 2020 14:45:45 +0200
Subject: [PATCH 2/2] Restore sys.path after importing test modules

Ref: https://github.com/pytest-dev/pytest/issues/5147#issuecomment-607752141
---
 src/_pytest/python.py         |  4 ++++
 testing/python/collect.py     | 15 +++++++++++++++
 testing/test_assertrewrite.py |  1 +
 testing/test_monkeypatch.py   |  4 +++-
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/_pytest/python.py b/src/_pytest/python.py
index 372631f107d..33ef086b0d0 100644
--- a/src/_pytest/python.py
+++ b/src/_pytest/python.py
@@ -515,6 +515,7 @@ def _importtestmodule(self) -> ModuleType:
         # we assume we are only called once per module
         importmode = self.config.getoption("--import-mode")
         fspath = self.fspath
+        old_sys_path = sys.path[:] if importmode != "importlib" else None
         try:
             mod = fspath.pyimport(ensuresyspath=importmode)
         except SyntaxError:
@@ -554,6 +555,9 @@ def _importtestmodule(self) -> ModuleType:
                 "or @pytest.mark.skipif decorators instead, and to skip a "
                 "module use `pytestmark = pytest.mark.{skip,skipif}."
             )
+        finally:
+            if old_sys_path:
+                sys.path[:] = old_sys_path
         self.config.pluginmanager.consider_module(mod)
         return mod
 
diff --git a/testing/python/collect.py b/testing/python/collect.py
index 7062740b88c..eb5eca9d58a 100644
--- a/testing/python/collect.py
+++ b/testing/python/collect.py
@@ -56,6 +56,21 @@ def test():
             reprec = testdir.inline_run()
             reprec.assertoutcome(passed=1)
 
+    @pytest.mark.parametrize("import_mode", ("append", "prepend", "importlib"))
+    def test__importtestmodule_restores_sys_path(self, import_mode, testdir):
+        p1 = testdir.makepyfile(
+            """
+            import sys
+
+            def test():
+                assert sys.path == {!r}
+            """.format(
+                sys.path
+            )
+        )
+        reprec = testdir.inline_run("--import-mode={}".format(import_mode), str(p1))
+        reprec.assertoutcome(passed=1)
+
     def test_syntax_error_in_module(self, testdir):
         modcol = testdir.getmodulecol("this is a syntax error")
         pytest.raises(modcol.CollectError, modcol.collect)
diff --git a/testing/test_assertrewrite.py b/testing/test_assertrewrite.py
index 36652dee54f..268c0ad77ff 100644
--- a/testing/test_assertrewrite.py
+++ b/testing/test_assertrewrite.py
@@ -1070,6 +1070,7 @@ def test_loader():
                 assert file.reloaded()
             """,
         )
+        testdir.syspathinsert()
         result = testdir.runpytest()
         result.stdout.fnmatch_lines(["* 1 passed*"])
 
diff --git a/testing/test_monkeypatch.py b/testing/test_monkeypatch.py
index 72f4cc85b9c..fd96df4b829 100644
--- a/testing/test_monkeypatch.py
+++ b/testing/test_monkeypatch.py
@@ -5,6 +5,7 @@
 
 import pytest
 from _pytest.monkeypatch import MonkeyPatch
+from _pytest.pytester import Testdir
 
 
 @pytest.fixture
@@ -318,7 +319,8 @@ def f():
     )
 
 
-def test_importerror(testdir):
+def test_importerror(testdir: Testdir) -> None:
+    testdir.syspathinsert()
     p = testdir.mkpydir("package")
     p.join("a.py").write(
         textwrap.dedent(