Add PYTEST_VERSION environment variable (#12190)

Among other things, it can be used to check if a code is running from within a pytest session.

Fixes #9502

AUTHORS

@@ -118,6 +118,7 @@ Daw-Ran Liou
 Debi Mishra
 Denis Kirisov
 Denivy Braiam Rück
+Dheeraj C K
 Dhiren Serai
 Diego Russo
 Dmitry Dygalo

changelog/9502.improvement.rst

@@ -0,0 +1 @@
+Added :envvar:`PYTEST_VERSION` environment variable which is defined at the start of the pytest session and undefined afterwards. It contains the value of ``pytest.__version__``, and among other things can be used to easily check if code is running from within a pytest run.

doc/en/reference/reference.rst

@@ -1117,6 +1117,11 @@ When set (regardless of value), pytest acknowledges that is running in a CI proc
 This contains a command-line (parsed by the py:mod:`shlex` module) that will be **prepended** to the command line given
 by the user, see :ref:`adding default options` for more information.
 
+.. envvar:: PYTEST_VERSION
+
+This environment variable is defined at the start of the pytest session and is undefined afterwards.
+It contains the value of ``pytest.__version__``, and among other things can be used to easily check if a code is running from within a pytest run.
+
 .. envvar:: PYTEST_CURRENT_TEST
 
 This is not meant to be set by users, but is set by pytest internally with the name of the current test so other

src/_pytest/config/__init__.py

@@ -50,6 +50,7 @@ from .compat import PathAwareHookProxy
 from .exceptions import PrintHelp as PrintHelp
 from .exceptions import UsageError as UsageError
 from .findpaths import determine_setup
+from _pytest import __version__
 import _pytest._code
 from _pytest._code import ExceptionInfo
 from _pytest._code import filter_traceback
@@ -151,7 +152,9 @@ def main(
 
     :returns: An exit code.
     """
+    old_pytest_version = os.environ.get("PYTEST_VERSION")
     try:
+        os.environ["PYTEST_VERSION"] = __version__
         try:
             config = _prepareconfig(args, plugins)
         except ConftestImportFailure as e:
@@ -186,6 +189,11 @@ def main(
         for msg in e.args:
             tw.line(f"ERROR: {msg}\n", red=True)
         return ExitCode.USAGE_ERROR
+    finally:
+        if old_pytest_version is None:
+            os.environ.pop("PYTEST_VERSION", None)
+        else:
+            os.environ["PYTEST_VERSION"] = old_pytest_version
 
 
 def console_main() -> int:

testing/test_runner.py

@@ -1094,3 +1094,20 @@ def test_outcome_exception_bad_msg() -> None:
     with pytest.raises(TypeError) as excinfo:
         OutcomeException(func)  # type: ignore
     assert str(excinfo.value) == expected
+
+
+def test_pytest_version_env_var(pytester: Pytester, monkeypatch: MonkeyPatch) -> None:
+    os.environ["PYTEST_VERSION"] = "old version"
+    pytester.makepyfile(
+        """
+        import pytest
+        import os
+
+
+        def test():
+            assert os.environ.get("PYTEST_VERSION") == pytest.__version__
+    """
+    )
+    result = pytester.runpytest_inprocess()
+    assert result.ret == ExitCode.OK
+    assert os.environ["PYTEST_VERSION"] == "old version"