Docs: Updates docs for redux framework (#20377)

* Docs: Updates docs for redux framework

* Update contribute/style-guides/redux.md

Co-Authored-By: Marcus Olsson <olsson.e.marcus@gmail.com>

* Update contribute/style-guides/redux.md

Co-Authored-By: Marcus Olsson <olsson.e.marcus@gmail.com>

* Update contribute/style-guides/redux.md

Co-Authored-By: Marcus Olsson <olsson.e.marcus@gmail.com>

* Update contribute/style-guides/redux.md

Co-Authored-By: Marcus Olsson <olsson.e.marcus@gmail.com>

* Docs: Updates after PR comments

* Update redux.md

contribute/style-guides/redux.md

@@ -5,7 +5,7 @@ To reduce the amount of boilerplate code used to create a strongly typed redux s
 `+` Much less boilerplate code
 `-` Non Redux standard api
 
-## New core functionality
+## Core functionality
 
 ### actionCreatorFactory
 
@@ -117,13 +117,13 @@ Type '{ nonExistingProperty: string; data: string[]; }' is not assignable to typ
   Object literal may only specify known properties, and 'nonExistingProperty' does not exist in type 'ExampleReducerState'. [2322]
 ```
 
-## New test functionality
+## Test functionality
 
 ### reducerTester
 
 Fluent API that simplifies the testing of reducers
 
-#### Example
+#### Usage
 
 ```typescript
 reducerTester()
@@ -131,3 +131,32 @@ reducerTester()
   .whenActionIsDispatched(someAction('reducer tests'))
   .thenStateShouldEqual({ ...initialState, data: 'reducer tests' });
 ```
+
+#### Complex usage
+Sometimes you encounter a `resulting state` that contains properties that are hard to compare, such as `Dates`, but you still want to compare that other props in state are correct.
+
+Then you can use `thenStatePredicateShouldEqual` function on `reducerTester` that will return the `resulting state` so that you can expect upon individual properties..
+
+```typescript
+reducerTester()
+  .givenReducer(someReducer, initialState)
+  .whenActionIsDispatched(someAction('reducer tests'))
+  .thenStatePredicateShouldEqual(resultingState => {
+    expect(resultingState.data).toEqual('reducer tests');
+    return true;  
+  });
+```
+
+### thunkTester
+
+Fluent API that simplifies the testing of thunks.
+
+#### Usage
+
+```typescript
+const dispatchedActions = await thunkTester(initialState)
+    .givenThunk(someThunk)
+    .whenThunkIsDispatched(arg1, arg2, arg3);
+
+expect(dispatchedActions).toEqual([someAction('reducer tests')]);
+```