Better checking that ray.init() has been called. (#10261)

python/ray/tests/test_error_ray_not_initialized.py

@@ -0,0 +1,54 @@
+import sys
+
+import pytest
+
+import ray
+
+
+def test_errors_before_initializing_ray():
+    @ray.remote
+    def f():
+        pass
+
+    @ray.remote
+    class Foo:
+        pass
+
+    api_methods = [
+        f.remote,
+        Foo.remote,
+        ray.actors,
+        lambda: ray.cancel(None),  # Not valid API usage.
+        lambda: ray.get([]),
+        lambda: ray.get_actor("name"),
+        ray.get_gpu_ids,
+        ray.get_resource_ids,
+        ray.get_webui_url,
+        ray.jobs,
+        lambda: ray.kill(None),  # Not valid API usage.
+        ray.nodes,
+        ray.objects,
+        lambda: ray.put(1),
+        lambda: ray.wait([])
+    ]
+
+    def test_exceptions_raised():
+        for api_method in api_methods:
+            print(api_method)
+            with pytest.raises(
+                    ray.exceptions.RayConnectionError,
+                    match="Ray has not been started yet."):
+                api_method()
+
+    test_exceptions_raised()
+
+    # Make sure that the exceptions are still raised after Ray has been
+    # started and shutdown.
+    ray.init(num_cpus=0)
+    ray.shutdown()
+
+    test_exceptions_raised()
+
+
+if __name__ == "__main__":
+    sys.exit(pytest.main(["-v", __file__]))