testing readme grammar fix (#3391)

Author: moritzvonberg

tests/README.md

@@ -116,12 +116,12 @@ TagContentConverter should return correct values for valid input.
 
 ## Mocking
 
-As we are trying to test our "units" of code independently, we want to make sure that we do not rely objects and data generated by "external" code. If we we did, then we wouldn't know if the failure we're observing was caused by the code we are actually trying to test or something external to it.
+As we are trying to test our "units" of code independently, we want to make sure that we do not rely on objects and data generated by "external" code. If we we did, then we wouldn't know if the failure we're observing was caused by the code we are actually trying to test or something external to it.
 
 
-However, the features that we are trying to test often depend on those objects generated by external pieces of code. It would be difficult to test a bot command without having access to a `Context` instance. Fortunately, there's a solution for that: we use fake objects that act like the true object. We call these fake objects "mocks".
+However, the features that we are trying to test often depend on objects generated by external pieces of code. For example, it would be difficult to test a bot command without having access to a `Context` instance. Fortunately, there's a solution for that: we use fake objects that act like the true object. We call these fake objects "mocks".
 
-To create these mock object, we mainly use the [`unittest.mock`](https://docs.python.org/3/library/unittest.mock.html) module. In addition, we have also defined a couple of specialized mock objects that mock specific `discord.py` types (see the section on the below.).
+To create these mock objects, we mainly use the [`unittest.mock`](https://docs.python.org/3/library/unittest.mock.html) module. In addition, we have also defined a couple of specialized mock objects that mock specific `discord.py` types (see the section about them below.).
 
 An example of mocking is when we provide a command with a mocked version of `discord.ext.commands.Context` object instead of a real `Context` object. This makes sure we can then check (_assert_) if the `send` method of the mocked Context object was called with the correct message content (without having to send a real message to the Discord API!):