update documentation

API.md

@@ -41,6 +41,7 @@
     -   [setupRenderingContext](#setuprenderingcontext)
     -   [teardownRenderingContext](#teardownrenderingcontext)
     -   [setApplication](#setapplication)
+    -   [getApplication](#getapplication)
     -   [setupApplicationContext](#setupapplicationcontext)
     -   [teardownApplicationContext](#teardownapplicationcontext)
     -   [validateErrorHandler](#validateerrorhandler)
@@ -512,6 +513,12 @@ Responsible for:
 
 Returns **[Promise](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Promise)<void>** resolves when settled
 
+### getApplication
+
+Retrieves the application instance stored by setApplication.
+
+-   Used by `setupContext`.
+
 ### setApplication
 
 Stores the provided application instance so that tests being ran will be aware of the application under test.