[Bug Fix] Pytester.syspathinsert() has no effect when using runpytest_subprocess() . closes #10651

AUTHORS

@@ -320,6 +320,7 @@ Oliver Bestwalter
 Omar Kohl
 Omer Hadari
 Ondřej Súkup
+Orel Damari
 Oscar Benjamin
 Parth Patel
 Patrick Hayes

changelog/10651.bugfix.rst

@@ -0,0 +1 @@
+Fixed bug where the `Pytester.syspathinsert` has no effect when using subprocess.

src/_pytest/pytester.py

@@ -689,6 +689,7 @@ def __init__(
  self._request.addfinalizer(self._finalize)
  self._method = self._request.config.getoption("--runpytest")
  self._test_tmproot = tmp_path_factory.mktemp(f"tmp-{name}", numbered=True)
+ self._prepended_syspaths: list[Path] = []
 
  self._monkeypatch = mp = monkeypatch
  self.chdir()
@@ -900,7 +901,9 @@ def syspathinsert(self, path: str | os.PathLike[str] | None = None) -> None:
  if path is None:
  path = self.path
 
- self._monkeypatch.syspath_prepend(str(path))
+ path_obj = Path(path)
+ self._monkeypatch.syspath_prepend(str(path_obj))
+ self._prepended_syspaths.append(path_obj)
 
  def mkdir(self, name: str | os.PathLike[str]) -> Path:
  """Create a new (sub)directory.
@@ -1337,10 +1340,16 @@ def popen(
 
  You probably want to use :py:meth:`run` instead.
  """
- env = os.environ.copy()
- env["PYTHONPATH"] = os.pathsep.join(
- filter(None, [os.getcwd(), env.get("PYTHONPATH", "")])
+ env = kw.pop("env", None) or os.environ.copy()
+ pythonpath = env.get("PYTHONPATH", "")
+
+ paths_to_add = [os.getcwd(), *self._prepended_syspaths]
+
+ pythonpath = os.pathsep.join(
+ filter(None, [*map(str, paths_to_add), pythonpath])
  )
+
+ env["PYTHONPATH"] = pythonpath
  kw["env"] = env
 
  if stdin is self.CLOSE_STDIN:
@@ -1365,6 +1374,7 @@ def run(
  *cmdargs: str | os.PathLike[str],
  timeout: float | None = None,
  stdin: NotSetType | bytes | IO[Any] | int = CLOSE_STDIN,
+ env: dict[str, str] | None = None,
  ) -> RunResult:
  """Run a command with arguments.
 
@@ -1413,6 +1423,7 @@ def run(
  stdout=f1,
  stderr=f2,
  close_fds=(sys.platform != "win32"),
+ env=env,
  )
  if popen.stdin is not None:
  popen.stdin.close()
@@ -1488,8 +1499,19 @@ def runpytest_subprocess(
  plugins = [x for x in self.plugins if isinstance(x, str)]
  if plugins:
  args = ("-p", plugins[0], *args)
- args = self._getpytestargs() + args
- return self.run(*args, timeout=timeout)
+
+ env = os.environ.copy()
+ pythonpath = env.get("PYTHONPATH", "")
+
+ # Add all prepended syspaths to PYTHONPATH
+ prepended_paths = [str(path) for path in self._prepended_syspaths]
+ pythonpath = os.pathsep.join(filter(None, [*prepended_paths, pythonpath]))
+
+ env["PYTHONPATH"] = pythonpath
+
+ return self.run(
+ *[sys.executable, "-m", "pytest", *args], timeout=timeout, env=env
+ )
 
  def spawn_pytest(self, string: str, expect_timeout: float = 10.0) -> pexpect.spawn:
  """Run pytest using pexpect.

testing/test_pytester.py

@@ -835,3 +835,37 @@ def test_two():
  result.assert_outcomes(passed=1, deselected=1)
  # If deselected is not passed, it is not checked at all.
  result.assert_outcomes(passed=1)
+
+
+def test_syspathinsert__in_process__path_exists(pytester: Pytester):
+ some_dir = "abcd"
+ pytester.syspathinsert(some_dir)
+ pytester.makepyfile(
+ f"""
+ import sys
+
+ def test_foo():
+ assert "{some_dir}" in sys.path
+ """
+ )
+
+ result = pytester.runpytest_inprocess()
+
+ result.assert_outcomes(passed=1)
+
+
+def test_syspathinsert__sub_process__path_exists(pytester: Pytester):
+ some_dir = "abcd"
+ pytester.syspathinsert(some_dir)
+ pytester.makepyfile(
+ f"""
+ import sys
+
+ def test_foo():
+ assert "{some_dir}" in sys.path
+ """
+ )
+
+ result = pytester.runpytest_subprocess()
+
+ result.assert_outcomes(passed=1)