test: run tests with DEVMODE

nedbat · nedbat · commit 2e20eb76f3a4 · 2025-12-10T09:34:39.000-05:00
diff --git a/tests/test_concurrency.py b/tests/test_concurrency.py
@@ -489,6 +489,9 @@ def try_multiprocessing_code(
             """,
         )
 
+        # Dev mode turns on deprecation warnings that some concurrency
+        # libraries issue. We don't need to see those.
+        self.del_environ("PYTHONDEVMODE")
         cmd = f"coverage run {args} multi.py {start_method}"
         _, out = self.run_command_status(cmd)
         expected_cant_trace = cant_trace_msg(concurrency, the_module)
diff --git a/tests/test_report.py b/tests/test_report.py
@@ -880,16 +880,17 @@ def test_report_with_chdir(self) -> None:
             print("Line One")
             os.chdir("subdir")
             print("Line Two")
-            print(open("something", encoding="utf-8").read())
+            with open("something", encoding="utf-8") as f:
+                print(f.read())
             """,
         )
         self.make_file("subdir/something", "hello")
         out = self.run_command("coverage run --source=. chdir.py")
         assert out == "Line One\nLine Two\nhello\n"
         report = self.report_from_command("coverage report")
-        assert self.last_line_squeezed(report) == "TOTAL 5 0 100%"
+        assert self.last_line_squeezed(report) == "TOTAL 6 0 100%"
         report = self.report_from_command("coverage report --format=markdown")
-        assert self.last_line_squeezed(report) == "| **TOTAL** | **5** | **0** | **100%** |"
+        assert self.last_line_squeezed(report) == "| **TOTAL** | **6** | **0** | **100%** |"
 
     def test_bug_156_file_not_run_should_be_zero(self) -> None:
         # https://github.com/coveragepy/coveragepy/issues/156
diff --git a/tox.ini b/tox.ini
@@ -31,7 +31,9 @@ setenv =
     pypy3{,10,11}: COVERAGE_TEST_CORES=pytrace
     PYTHONWARNDEFAULTENCODING=1
     PYTHONWARNINGS=ignore::EncodingWarning:pip._internal.utils.subprocess,ignore::EncodingWarning:pip._internal.configuration
-    # Disable CPython's color output
+    # Try to be strict during testing. https://docs.python.org/3/library/devmode.html
+    PYTHONDEVMODE=1
+    # Disable CPython's color output.
     PYTHON_COLORS=0
 
 # $set_env.py: COVERAGE_PIP_ARGS - Extra arguments for `pip install`

Original file line number	Diff line number	Diff line change
`@@ -489,6 +489,9 @@ def try_multiprocessing_code(`
`489`	`489`	`""",`
`490`	`490`	`)`
`491`	`491`
	`492`	`+ # Dev mode turns on deprecation warnings that some concurrency`
	`493`	`+ # libraries issue. We don't need to see those.`
	`494`	`+ self.del_environ("PYTHONDEVMODE")`
`492`	`495`	`cmd = f"coverage run {args} multi.py {start_method}"`
`493`	`496`	`_, out = self.run_command_status(cmd)`
`494`	`497`	`expected_cant_trace = cant_trace_msg(concurrency, the_module)`