test: more tests of debug output control

coverage/debug.py

@@ -279,7 +279,7 @@ def filter_text(text: str, filters: Iterable[Callable[[str], str]]) -> str:
     return text + ending
 
 
-class CwdTracker:                                   # pragma: debugging
+class CwdTracker:
     """A class to add cwd info to debug messages."""
     def __init__(self) -> None:
         self.cwd: Optional[str] = None
@@ -293,7 +293,7 @@ def filter(self, text: str) -> str:
         return text
 
 
-class DebugOutputFile:                              # pragma: debugging
+class DebugOutputFile:
     """A file-like object that includes pid and cwd information."""
     def __init__(
         self,

tests/test_debug.py

@@ -239,22 +239,31 @@ def debug_sys(self) -> None:
 
     def test_stderr_default(self) -> None:
         self.debug_sys()
-        assert_good_debug_sys(self.stderr())
+        out, err = self.stdouterr()
+        assert out == ""
+        assert_good_debug_sys(err)
 
     def test_envvar(self) -> None:
         self.set_environ("COVERAGE_DEBUG_FILE", "debug.out")
         self.debug_sys()
-        assert self.stderr() == ""
+        assert self.stdouterr() == ("", "")
         with open("debug.out") as f:
             assert_good_debug_sys(f.read())
 
     def test_config_file(self) -> None:
         self.make_file(".coveragerc", "[run]\ndebug_file = lotsa_info.txt")
         self.debug_sys()
-        assert self.stderr() == ""
+        assert self.stdouterr() == ("", "")
         with open("lotsa_info.txt") as f:
             assert_good_debug_sys(f.read())
 
+    def test_stdout_alias(self) -> None:
+        self.set_environ("COVERAGE_DEBUG_FILE", "stdout")
+        self.debug_sys()
+        out, err = self.stdouterr()
+        assert err == ""
+        assert_good_debug_sys(out)
+
 
 def f_one(*args: Any, **kwargs: Any) -> str:
     """First of the chain of functions for testing `short_stack`."""