chore: import upstream snapshot with attribution

tests/dangerously_run_function_in_subprocess.py

@@ -0,0 +1,46 @@
+import inspect
+import subprocess
+import sys
+import textwrap
+from typing import Any, Callable
+
+
+def dangerously_run_function_in_subprocess(func: Callable[[], Any]) -> tuple[str, str, int]:
+    """**Use with caution! This should _only_ be used with trusted code!**
+
+    Extracts a function's source and runs it in a separate subprocess. Returns stdout, stderr, and return code
+    from the subprocess.
+
+    This is useful for tests where an isolated environment is required.
+
+    The function to be called must not have any arguments and must not have any closures over the scope in which is was
+    defined.
+
+    Any modules that the function depends on must be imported inside the function.
+    """
+
+    source_code = inspect.getsource(func)
+
+    # Must dedent the source code to avoid indentation errors
+    dedented_source_code = textwrap.dedent(source_code)
+
+    # Get the function name so we can call it in the subprocess
+    func_name = func.__name__
+
+    # Create a script that calls the function
+    script = f"""
+import sys
+
+{dedented_source_code}
+
+if __name__ == "__main__":
+    {func_name}()
+"""
+
+    result = subprocess.run(
+        [sys.executable, "-c", textwrap.dedent(script)],  # Run the script in a subprocess
+        capture_output=True,  # Capture stdout and stderr
+        text=True,
+    )
+
+    return result.stdout, result.stderr, result.returncode