Add context manager for changing directories temporarily

Author: bittner

cli_test_helpers/__init__.py

@@ -5,8 +5,9 @@
 __all__ = [
     "ArgvContext",
     "EnvironContext",
+    "RandomDirectoryContext",
     "shell",
 ]
 
 from .commands import shell
-from .decorators import ArgvContext, EnvironContext
+from .decorators import ArgvContext, EnvironContext, RandomDirectoryContext

cli_test_helpers/decorators.py

@@ -3,7 +3,9 @@
 """
 
 import contextlib
+import os
 import sys
+from tempfile import TemporaryDirectory
 from unittest.mock import patch
 
 __all__ = []
@@ -50,3 +52,21 @@ def __enter__(self):
         for key in self.clear_variables:
             with contextlib.suppress(KeyError):
                 self.in_dict.pop(key)
+
+
+class RandomDirectoryContext(TemporaryDirectory):
+    """
+    Change the execution directory to a random location, temporarily.
+    """
+
+    def __enter__(self):
+        """Create a temporary directory and ``cd`` into it."""
+        self.__prev_dir = os.getcwd()
+        super().__enter__()
+        os.chdir(self.name)
+        return self.name
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        """Return to the original directory before execution."""
+        os.chdir(self.__prev_dir)
+        return super().__exit__(exc_type, exc_value, traceback)

pyproject.toml

@@ -67,6 +67,7 @@ extend-ignore = [
     "D203",
     "D205",
     "D212",
+    "PTH109",
     "Q000",
 ]
 

tests/test_decorators.py

@@ -3,7 +3,7 @@
 import os
 import sys
 
-from cli_test_helpers import ArgvContext, EnvironContext
+from cli_test_helpers import ArgvContext, EnvironContext, RandomDirectoryContext
 
 
 def test_argv_context():
@@ -45,3 +45,20 @@ def test_environ_context():
     assert os.environ == old_environ, "object os.environ was not restored"
     assert os.getenv("PATH") == old_path, "env var PATH was not restored"
     assert os.getenv("FOO") is None, "env var FOO was not cleared"
+
+
+def test_random_directory_context():
+    """
+    In a directory context, are we effectively in a different location?
+    """
+    before_dir = os.getcwd()
+
+    with RandomDirectoryContext() as random_dir:
+        new_dir = os.getcwd()
+
+        assert new_dir == random_dir, "Does't behave like TemporaryDirectory"
+        assert new_dir != before_dir, "Context not in a different file system location"
+
+    after_dir = os.getcwd()
+
+    assert after_dir == before_dir, "Execution directory not restored to original"