diff --git a/ci/travis/ci.sh b/ci/travis/ci.sh
index 8e639933a..600311255 100755
--- a/ci/travis/ci.sh
+++ b/ci/travis/ci.sh
@@ -125,31 +125,23 @@ test_python() {
       -python/ray/tests:test_actor_failures
       -python/ray/tests:test_advanced_2
       -python/ray/tests:test_advanced_3
-      -python/ray/tests:test_array
-      -python/ray/tests:test_asyncio
+      -python/ray/tests:test_array  # timeout
       -python/ray/tests:test_autoscaler_aws
       -python/ray/tests:test_autoscaler_yaml
-      -python/ray/tests:test_cancel
       -python/ray/tests:test_component_failures
       -python/ray/tests:test_cython
-      -python/ray/tests:test_dynres
       -python/ray/tests:test_failure
       -python/ray/tests:test_global_gc
-      -python/ray/tests:test_global_state
-      -python/ray/tests:test_iter
-      -python/ray/tests:test_memory_scheduling
       -python/ray/tests:test_memstat
       -python/ray/tests:test_metrics
       -python/ray/tests:test_multi_node
       -python/ray/tests:test_multi_node_2
-      -python/ray/tests:test_multinode_failures_2
-      -python/ray/tests:test_multiprocessing
+      -python/ray/tests:test_multiprocessing  # flaky
       -python/ray/tests:test_node_manager
       -python/ray/tests:test_object_manager
       -python/ray/tests:test_projects
-      -python/ray/tests:test_queue
-      -python/ray/tests:test_ray_init
-      -python/ray/tests:test_reconstruction
+      -python/ray/tests:test_queue  # timeout
+      -python/ray/tests:test_reconstruction  # UnreconstructableError
       -python/ray/tests:test_stress
       -python/ray/tests:test_stress_sharded
       -python/ray/tests:test_webui
diff --git a/python/ray/serve/tests/test_failure.py b/python/ray/serve/tests/test_failure.py
index 4e7eb7f80..959384fa2 100644
--- a/python/ray/serve/tests/test_failure.py
+++ b/python/ray/serve/tests/test_failure.py
@@ -214,7 +214,8 @@ def test_worker_replica_failure(serve_instance):
         def __call__(self):
             pass
 
-    temp_path = tempfile.gettempdir() + "/" + serve.utils.get_random_letters()
+    temp_path = os.path.join(tempfile.gettempdir(),
+                             serve.utils.get_random_letters())
     serve.create_backend("replica_failure", Worker, temp_path)
     serve.update_backend_config("replica_failure", {"num_replicas": 2})
     serve.create_endpoint(
diff --git a/python/ray/tests/BUILD b/python/ray/tests/BUILD
index f86445a76..611920652 100644
--- a/python/ray/tests/BUILD
+++ b/python/ray/tests/BUILD
@@ -1,8 +1,8 @@
 SRCS = [] + select({
-    "@bazel_tools//src/conditions:windows": [
+    "@bazel_tools//src/conditions:windows": glob([
         # TODO(mehrdadn): This should be added for all platforms once resulting errors are fixed
-        "conftest.py",
-    ],
+        "**/conftest.py",
+    ]),
     "//conditions:default": [],
 })
 
diff --git a/python/ray/tests/conftest.py b/python/ray/tests/conftest.py
index 01d993da1..766fc7843 100644
--- a/python/ray/tests/conftest.py
+++ b/python/ray/tests/conftest.py
@@ -182,13 +182,13 @@ def call_ray_start(request):
     # Disconnect from the Ray cluster.
     ray.shutdown()
     # Kill the Ray cluster.
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "stop"])
 
 
 @pytest.fixture
 def call_ray_stop_only():
     yield
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "stop"])
 
 
 @pytest.fixture()
diff --git a/python/ray/tests/test_autoscaler.py b/python/ray/tests/test_autoscaler.py
index 2d5cd76e7..8d7046d6f 100644
--- a/python/ray/tests/test_autoscaler.py
+++ b/python/ray/tests/test_autoscaler.py
@@ -306,7 +306,7 @@ class AutoscalingTest(unittest.TestCase):
         return self.provider
 
     def write_config(self, config):
-        path = self.tmpdir + "/simple.yaml"
+        path = os.path.join(self.tmpdir, "simple.yaml")
         with open(path, "w") as f:
             f.write(yaml.dump(config))
         return path
diff --git a/python/ray/tests/test_autoscaler_yaml.py b/python/ray/tests/test_autoscaler_yaml.py
index da17e5d2e..6c8b76e90 100644
--- a/python/ray/tests/test_autoscaler_yaml.py
+++ b/python/ray/tests/test_autoscaler_yaml.py
@@ -8,12 +8,12 @@ import tempfile
 from ray.autoscaler.util import prepare_config, validate_config
 from ray.test_utils import recursive_fnmatch
 
-RAY_PATH = os.path.abspath(os.path.join(__file__, "../../"))
+RAY_PATH = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
 CONFIG_PATHS = recursive_fnmatch(
     os.path.join(RAY_PATH, "autoscaler"), "*.yaml")
 
 CONFIG_PATHS += recursive_fnmatch(
-    os.path.join(RAY_PATH, "tune/examples/"), "*.yaml")
+    os.path.join(RAY_PATH, "tune", "examples"), "*.yaml")
 
 
 class AutoscalingConfigTest(unittest.TestCase):
@@ -52,7 +52,8 @@ class AutoscalingConfigTest(unittest.TestCase):
             pass
 
     def testInvalidConfig(self):
-        self._test_invalid_config("tests/additional_property.yaml")
+        self._test_invalid_config(
+            os.path.join("tests", "additional_property.yaml"))
 
 
 if __name__ == "__main__":
diff --git a/python/ray/tests/test_multi_node.py b/python/ray/tests/test_multi_node.py
index 21ad6f28a..e31c1f574 100644
--- a/python/ray/tests/test_multi_node.py
+++ b/python/ray/tests/test_multi_node.py
@@ -359,66 +359,66 @@ def test_calling_start_ray_head(call_ray_stop_only):
     # should also test the non-head node code path.
 
     # Test starting Ray with no arguments.
-    subprocess.check_output(["ray", "start", "--head"])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "start", "--head"])
+    subprocess.check_call(["ray", "stop"])
 
     # Test starting Ray with a redis port specified.
-    subprocess.check_output(["ray", "start", "--head"])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "start", "--head"])
+    subprocess.check_call(["ray", "stop"])
 
     # Test starting Ray with a node IP address specified.
-    subprocess.check_output(
+    subprocess.check_call(
         ["ray", "start", "--head", "--node-ip-address", "127.0.0.1"])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "stop"])
 
     # Test starting Ray with the object manager and node manager ports
     # specified.
-    subprocess.check_output([
+    subprocess.check_call([
         "ray", "start", "--head", "--object-manager-port", "12345",
         "--node-manager-port", "54321"
     ])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "stop"])
 
     # Test starting Ray with the worker port range specified.
-    subprocess.check_output([
+    subprocess.check_call([
         "ray", "start", "--head", "--min-worker-port", "50000",
         "--max-worker-port", "51000"
     ])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "stop"])
 
     # Test starting Ray with the number of CPUs specified.
-    subprocess.check_output(["ray", "start", "--head", "--num-cpus", "2"])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "start", "--head", "--num-cpus", "2"])
+    subprocess.check_call(["ray", "stop"])
 
     # Test starting Ray with the number of GPUs specified.
-    subprocess.check_output(["ray", "start", "--head", "--num-gpus", "100"])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "start", "--head", "--num-gpus", "100"])
+    subprocess.check_call(["ray", "stop"])
 
     # Test starting Ray with the max redis clients specified.
-    subprocess.check_output(
+    subprocess.check_call(
         ["ray", "start", "--head", "--redis-max-clients", "100"])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "stop"])
 
     if "RAY_USE_NEW_GCS" not in os.environ:
         # Test starting Ray with redis shard ports specified.
-        subprocess.check_output([
+        subprocess.check_call([
             "ray", "start", "--head", "--redis-shard-ports", "6380,6381,6382"
         ])
-        subprocess.check_output(["ray", "stop"])
+        subprocess.check_call(["ray", "stop"])
 
         # Test starting Ray with all arguments specified.
-        subprocess.check_output([
+        subprocess.check_call([
             "ray", "start", "--head", "--redis-shard-ports", "6380,6381,6382",
             "--object-manager-port", "12345", "--num-cpus", "2", "--num-gpus",
             "0", "--redis-max-clients", "100", "--resources", "{\"Custom\": 1}"
         ])
-        subprocess.check_output(["ray", "stop"])
+        subprocess.check_call(["ray", "stop"])
 
     # Test starting Ray with invalid arguments.
     with pytest.raises(subprocess.CalledProcessError):
-        subprocess.check_output(
+        subprocess.check_call(
             ["ray", "start", "--head", "--address", "127.0.0.1:6379"])
-    subprocess.check_output(["ray", "stop"])
+    subprocess.check_call(["ray", "stop"])
 
     # Test --block. Killing a child process should cause the command to exit.
     blocked = subprocess.Popen(["ray", "start", "--head", "--block"])
diff --git a/python/ray/tests/test_projects.py b/python/ray/tests/test_projects.py
index b2d6b60da..48021fcf1 100644
--- a/python/ray/tests/test_projects.py
+++ b/python/ray/tests/test_projects.py
@@ -94,7 +94,8 @@ def run_test_project(project_dir, command, args):
 
 def test_session_start_default_project():
     result, mock_calls, test_dir = run_test_project(
-        "session-tests/project-pass", session_start, ["default"])
+        os.path.join("session-tests", "project-pass"), session_start,
+        ["default"])
 
     loaded_project = ray.projects.ProjectDefinition(test_dir)
     assert result.exit_code == 0
@@ -138,7 +139,8 @@ def test_session_start_default_project():
 
 def test_session_execute_default_project():
     result, mock_calls, test_dir = run_test_project(
-        "session-tests/project-pass", session_execute, ["default"])
+        os.path.join("session-tests", "project-pass"), session_execute,
+        ["default"])
 
     loaded_project = ray.projects.ProjectDefinition(test_dir)
     assert result.exit_code == 0
@@ -159,13 +161,14 @@ def test_session_execute_default_project():
     assert expected_commands == commands_executed
 
     result, mock_calls, test_dir = run_test_project(
-        "session-tests/project-pass", session_execute, ["--shell", "uptime"])
+        os.path.join("session-tests", "project-pass"), session_execute,
+        ["--shell", "uptime"])
     assert result.exit_code == 0
 
 
 def test_session_start_docker_fail():
-    result, _, _ = run_test_project("session-tests/with-docker-fail",
-                                    session_start, [])
+    result, _, _ = run_test_project(
+        os.path.join("session-tests", "with-docker-fail"), session_start, [])
 
     assert result.exit_code == 1
     assert ("Docker support in session is currently "
@@ -173,8 +176,9 @@ def test_session_start_docker_fail():
 
 
 def test_session_invalid_config_errored():
-    result, _, _ = run_test_project("session-tests/invalid-config-fail",
-                                    session_start, [])
+    result, _, _ = run_test_project(
+        os.path.join("session-tests", "invalid-config-fail"), session_start,
+        [])
 
     assert result.exit_code == 1
     assert "validation failed" in result.output
@@ -184,7 +188,7 @@ def test_session_invalid_config_errored():
 
 def test_session_create_command():
     result, mock_calls, test_dir = run_test_project(
-        "session-tests/commands-test", session_start,
+        os.path.join("session-tests", "commands-test"), session_start,
         ["first", "--a", "1", "--b", "2"])
 
     # Verify the project can be loaded.
@@ -202,7 +206,7 @@ def test_session_create_command():
 def test_session_create_multiple():
     for args in [{"a": "*", "b": "2"}, {"a": "1", "b": "*"}]:
         result, mock_calls, test_dir = run_test_project(
-            "session-tests/commands-test", session_start,
+            os.path.join("session-tests", "commands-test"), session_start,
             ["first", "--a", args["a"], "--b", args["b"]])
 
         loaded_project = ray.projects.ProjectDefinition(test_dir)
@@ -227,14 +231,14 @@ def test_session_create_multiple():
 
     # Using multiple wildcards shouldn't work
     result, mock_calls, test_dir = run_test_project(
-        "session-tests/commands-test", session_start,
+        os.path.join("session-tests", "commands-test"), session_start,
         ["first", "--a", "*", "--b", "*"])
     assert result.exit_code == 1
 
 
 def test_session_commands():
     result, mock_calls, test_dir = run_test_project(
-        "session-tests/commands-test", session_commands, [])
+        os.path.join("session-tests", "commands-test"), session_commands, [])
 
     assert "This is the first parameter" in result.output
     assert "This is the second parameter" in result.output
diff --git a/python/ray/tune/tests/test_run_experiment.py b/python/ray/tune/tests/test_run_experiment.py
index 98b7b1291..53ef55b15 100644
--- a/python/ray/tune/tests/test_run_experiment.py
+++ b/python/ray/tune/tests/test_run_experiment.py
@@ -95,7 +95,7 @@ class RunExperimentTest(unittest.TestCase):
                 return {"timesteps_this_iter": 1, "done": True}
 
             def _save(self, path):
-                checkpoint = path + "/checkpoint"
+                checkpoint = os.path.join(path, "checkpoint")
                 with open(checkpoint, "w") as f:
                     f.write("OK")
                 return checkpoint
@@ -116,7 +116,7 @@ class RunExperimentTest(unittest.TestCase):
                 return {"timesteps_this_iter": 1, "done": True}
 
             def _export_model(self, export_formats, export_dir):
-                path = export_dir + "/exported"
+                path = os.path.join(export_dir, "exported")
                 with open(path, "w") as f:
                     f.write("OK")
                 return {export_formats[0]: path}
diff --git a/python/ray/tune/tests/test_trial_scheduler.py b/python/ray/tune/tests/test_trial_scheduler.py
index ab01d1429..20bb90632 100644
--- a/python/ray/tune/tests/test_trial_scheduler.py
+++ b/python/ray/tune/tests/test_trial_scheduler.py
@@ -1145,7 +1145,7 @@ class E2EPopulationBasedTestingSuite(unittest.TestCase):
                 return {"mean_accuracy": self.training_iteration}
 
             def _save(self, path):
-                checkpoint = path + "/checkpoint"
+                checkpoint = os.path.join(path, "checkpoint")
                 with open(checkpoint, "w") as f:
                     f.write("OK")
                 return checkpoint
diff --git a/src/ray/object_manager/plasma/store_runner.cc b/src/ray/object_manager/plasma/store_runner.cc
index e8ca85378..e67b556f5 100644
--- a/src/ray/object_manager/plasma/store_runner.cc
+++ b/src/ray/object_manager/plasma/store_runner.cc
@@ -133,7 +133,11 @@ void PlasmaStoreRunner::Start() {
   ArrowLog::ShutDownArrowLog();
 }
 
-void PlasmaStoreRunner::Stop() { loop_->Stop(); }
+void PlasmaStoreRunner::Stop() {
+  if (loop_) {
+    loop_->Stop();
+  }
+}
 
 void PlasmaStoreRunner::Shutdown() {
   loop_->Shutdown();