Improve test cases doc

Author: wlsf82

docs/TestCases.md

@@ -1,8 +1,10 @@
 # Test cases
 
-Below is a list of test cases that could be covered by automated scripts for the **EngageSphere** application.
+Below is a list of test cases currently covered by automated scripts for the **EngageSphere** application.
 
-The tests should cover both the API and Graphical User Interface (GUI.)
+The tests cover both the API and Graphical User Interface (GUI.)
+
+> The GUI tests cover integrated frontend tests, accessibility (a11y) tests, and component tests.
 
 ## API
 
@@ -23,6 +25,10 @@ When sending a GET request to the `/customers` endpoint:
 
 ## GUI
 
+Below are the three kinds of GUI tests:
+
+### Frontend integrated
+
 - It filters by All sizes
 - It filters by Small size
 - It filters by Medium size
@@ -51,7 +57,7 @@ When sending a GET request to the `/customers` endpoint:
   - It finds no a11y issues in light mode
   - It finds no a11y issues in dark mode
 
-## Component
+### Component
 
 - `<CustomerDetails />`
   - It renders with contact details