More pragmas to fine-tune coverage of test code

metacov.ini

@@ -35,6 +35,10 @@ exclude_lines =
     # OS error conditions that we can't (or don't care to) replicate.
     pragma: cant happen
 
+    # Obscure bugs in specific versions of interpreters, and so probably no
+    # longer tested.
+    pragma: obscure
+
     # Jython needs special care.
     pragma: only jython
     skip.*Jython

tests/test_concurrency.py

@@ -464,7 +464,7 @@ def test_coverage_stop_in_threads():
     has_started_coverage = []
     has_stopped_coverage = []
 
-    def run_thread():
+    def run_thread():           # pragma: nested
         """Check that coverage is stopping properly in threads."""
         deadline = time.time() + 5
         ident = threading.currentThread().ident
@@ -480,11 +480,11 @@ def run_thread():
     cov = coverage.coverage()
     cov.start()
 
-    t = threading.Thread(target=run_thread)
-    t.start()
+    t = threading.Thread(target=run_thread)             # pragma: nested
+    t.start()                                           # pragma: nested
 
-    time.sleep(0.1)
-    cov.stop()
+    time.sleep(0.1)                                     # pragma: nested
+    cov.stop()                                          # pragma: nested
     time.sleep(0.1)
 
     assert has_started_coverage == [t.ident]
@@ -513,7 +513,7 @@ def test_thread_safe_save_data(tmpdir):
         for module_name in module_names:
             import_local_file(module_name)
 
-        def random_load():
+        def random_load():                              # pragma: nested
             """Import modules randomly to stress coverage."""
             while should_run[0]:
                 module_name = random.choice(module_names)
@@ -529,12 +529,12 @@ def random_load():
             cov = coverage.coverage()
             cov.start()
 
-            threads = [threading.Thread(target=random_load) for _ in range(10)]
-            should_run[0] = True
-            for t in threads:
+            threads = [threading.Thread(target=random_load) for _ in range(10)]     # pragma: nested
+            should_run[0] = True                    # pragma: nested
+            for t in threads:                       # pragma: nested
                 t.start()
 
-            time.sleep(duration)
+            time.sleep(duration)                    # pragma: nested
 
             cov.stop()
 
@@ -546,7 +546,7 @@ def random_load():
             for t in threads:
                 t.join()
 
-            if (not imported) and duration < 10:
+            if (not imported) and duration < 10:    # pragma: only failure
                 duration *= 2
 
     finally:

tests/test_process.py

@@ -610,7 +610,7 @@ def f():
         self.assertIn(msg, out)
 
     def test_note(self):
-        if env.PYPY and env.PY3 and env.PYPYVERSION[:3] == (5, 10, 0):
+        if env.PYPY and env.PY3 and env.PYPYVERSION[:3] == (5, 10, 0):      # pragma: obscure
             # https://bitbucket.org/pypy/pypy/issues/2729/pypy3-510-incorrectly-decodes-astral-plane
             self.skipTest("Avoid incorrect decoding astral plane JSON chars")
         self.make_file(".coveragerc", """\
@@ -767,7 +767,7 @@ def test_coverage_run_dashm_is_like_python_dashm(self):
         self.assert_tryexecfile_output(out_cov, out_py)
 
     def test_coverage_run_dir_is_like_python_dir(self):
-        if sys.version_info == (3, 5, 4, 'final', 0):       # pragma: not covered
+        if sys.version_info == (3, 5, 4, 'final', 0):       # pragma: obscure
             self.skipTest("3.5.4 broke this: https://bugs.python.org/issue32551")
         with open(TRY_EXECFILE) as f:
             self.make_file("with_main/__main__.py", f.read())