Allow non-threadsafe projects to be compatible with --tests-per-worker=1

pytest_parallel/__init__.py

@@ -56,12 +56,20 @@ def run_test(session, item, nextitem):
         raise session.Interrupted(session.shouldstop)
 
 
+def process_with_no_threads(config, queue, session, tests_per_worker, errors):
+    return do_work("Thread-0", queue, session, errors)
+
+
+
 def process_with_threads(config, queue, session, tests_per_worker, errors):
     # This function will be called from subprocesses, forked from the main
     # pytest process. First thing we need to do is to change config's value
     # so we know we are running as a worker.
     config.parallel_worker = True
 
+    if tests_per_worker < 2:
+      return process_with_no_threads(config, queue, session, tests_per_worker, errors)
+
     threads = []
     for _ in range(tests_per_worker):
         thread = ThreadWorker(queue, session, errors)
@@ -78,29 +86,33 @@ def __init__(self, queue, session, errors):
         self.errors = errors
 
     def run(self):
-        pickling_support.install()
-        while True:
-            try:
-                index = self.queue.get()
-                if index == 'stop':
-                    self.queue.task_done()
-                    break
-            except ConnectionRefusedError:
-                time.sleep(.1)
-                continue
-            item = self.session.items[index]
-            try:
-                run_test(self.session, item, None)
-            except BaseException:
-                import pickle
-                import sys
-
-                self.errors.put((self.name, pickle.dumps(sys.exc_info())))
-            finally:
-                try:
-                    self.queue.task_done()
-                except ConnectionRefusedError:
-                    pass
+      return do_work(self.name, self.queue, self.session, self.errors)
+
+
+def do_work(name, queue, session, errors):
+  pickling_support.install()
+  while True:
+      try:
+          index = queue.get()
+          if index == 'stop':
+              queue.task_done()
+              break
+      except ConnectionRefusedError:
+          time.sleep(.1)
+          continue
+      item = session.items[index]
+      try:
+          run_test(session, item, None)
+      except BaseException:
+          import pickle
+          import sys
+
+          errors.put((name, pickle.dumps(sys.exc_info())))
+      finally:
+          try:
+              queue.task_done()
+          except ConnectionRefusedError:
+              pass
 
 
 @pytest.mark.trylast
@@ -207,8 +219,25 @@ def __init__(self, config):
 
         self.workers = workers
 
+        # get the number of tests per worker
+        tests_per_worker = parse_config(config, 'tests_per_worker')
+        try:
+            if tests_per_worker == 'auto':
+                tests_per_worker = 50
+            if tests_per_worker:
+                tests_per_worker = int(tests_per_worker)
+            else:
+                tests_per_worker = 1
+        except ValueError:
+            raise ValueError(('tests_per_worker can only be '
+                              'an integer or "auto"'))
+        self.tests_per_worker = tests_per_worker
+
     @pytest.mark.tryfirst
     def pytest_sessionstart(self, session):
+        if self.tests_per_worker < 2:
+          return  # Don't need no stinking thread safety!
+
         # make the session threadsafe
         _pytest.runner.SetupState = ThreadLocalSetupState
 
@@ -231,26 +260,13 @@ def pytest_runtestloop(self, session):
         if session.config.option.collectonly:
             return True
 
-        # get the number of tests per worker
-        tests_per_worker = parse_config(session.config, 'tests_per_worker')
-        try:
-            if tests_per_worker == 'auto':
-                tests_per_worker = 50
-            if tests_per_worker:
-                tests_per_worker = int(tests_per_worker)
-                evenly_divided = math.ceil(len(session.items)/self.workers)
-                tests_per_worker = min(tests_per_worker, evenly_divided)
-            else:
-                tests_per_worker = 1
-        except ValueError:
-            raise ValueError(('tests_per_worker can only be '
-                              'an integer or "auto"'))
-
         if self.workers > 1:
             worker_noun, process_noun = ('workers', 'processes')
         else:
             worker_noun, process_noun = ('worker', 'process')
 
+        evenly_divided = math.ceil(len(session.items)/self.workers)
+        tests_per_worker = min(self.tests_per_worker, evenly_divided)
         if tests_per_worker > 1:
             test_noun, thread_noun = ('tests', 'threads')
         else:
@@ -328,7 +344,7 @@ def send_response(self, event_name, **arguments):
         self.responses_queue.put((event_name, arguments))
 
     def pytest_runtest_logreport(self, report):
-        # We want workers to report to it's master.
+        # We want workers to report to its master.
         # Without this "if", master will try to report to itself.
         if self._config.parallel_worker:
             data = self._config.hook.pytest_report_to_serializable(