Ability to run subscriptions code snippet as it is (#1296)

* Ability to run subscriptions code snippet as it is

Allows you to copy the snippet of code from this documentation and run it as is, without code changes. The "testing subscriptions" snippet has been updated for the same.

* Create Query class + Fix styling

Created Query class and also made the other requested changes on PR #1296

docs/operations/testing.md

@@ -102,6 +102,26 @@ async def test_mutaton():
 And finally, a test for our [`count` Subscription](docs/general/subscriptions.md):
 
 ```python
+import asyncio
+import pytest
+import strawberry
+
+@strawberry.type
+class Subscription:
+    @strawberry.subscription
+    async def count(self, target: int = 100) -> int:
+        for i in range(target):
+            yield i
+            await asyncio.sleep(0.5)
+
+@strawberry.type
+class Query:
+    @strawberry.field
+    def hello() -> str:
+        return "world"
+
+schema = strawberry.Schema(query=Query, subscription=Subscription)
+
 @pytest.mark.asyncio
 async def test_subscription():
     query = """