Write some text on client testing and development

docs/source/development/client.md

 # Frontend
 
-[comment]: # (TODO)
+Here it is described how to work with the frontend in the system.
 
 ## Working with TypeScript
 
-[comment]: # (TODO)
+The main programming languange used for the front end is TypeScript.
 
 ### npm
 

docs/source/testing/client.md

 # Testing the client
 
-[comment]: # (TODO)
+The clients tests are the files named `<name>.test.ts`.
\ No newline at end of file
+They test the file called `<name>.ts`.
+They are run using the [VS Code task](../development/vscode.md) `Unit tests`.

docs/source/testing/e2e.md

 # End to end tests
 
-[comment]: # (TODO)
+The end to end tests are tests that test the entire system, both the server and the client.
\ No newline at end of file
+They are stored in the folder `/client/src/e2e/`.
+Both the client and the server need to be running for the end to end tests to work.
+The tests are run using the [VS Code task](../development/vscode.md) `Run e2e tests`.