Charles Set-up

1. Download it from https://www.charlesproxy.com -- There's a free trial available. After that, usage is time-boxed to 1 hour per session, and a there's a 10 second delay every time you launch it.
2. Enable SSL proxying by following these instructions: https://www.charlesproxy.com/documentation/using-charles/ssl-certificates/
3. Install the certificate on your device (also described in the link above) and don't forget to change your wifi settings to point to the IP address of the machine running Charles. The IP address is available in Charles's Help menu > "Local IP address". Also, by default Charles uses port 8888.
4. At this point you should be able to run SimplyE and see the requests/responses that go out from your device, decrypted. If you still see them encrypted, try quitting and reopening Charles.

Focus

Charles shows EVERY url your device hits. I find very useful to "focus" on the hosts that I care about and hide everything else. To do this, choose View --> "Focused Hosts..." and enter these hosts:

	*.librarysimplified.org
	*.nypl.org
	*.bklynlibrary.org
	(or any other library URLs you are testing against)

This way Charles will highlight requests to those hosts and hide everything else under "Other Hosts."

Response Rewrite Set-up

To test how the app behaves when requests (for whatever reason) fail, it's really convenient to use the response rewrite feature that Charles offers.

1. From the Tools menu, choose "Rewrite..."
   
   
2. Click "Add" on the bottom left of the pop-up window to add a rewrite set.
3. Then add a URL you wish to rewrite. If you have used the app for a while as you were testing it out, you can just pick one of the URLs the app tried to reach. If you want to test the loading of a particular page in the app and you don't know which api call serves that page, clear the session with the "broom" icon in the toolbar, then load the page again on the device, and you will see its related URL show up.
   

   For example, in the image above I added 2 locations: one for the libraries list and one for Circulation manager authentication document.

   If the URL you're looking for does not appear in Charles, it might be because it's being cached by the app. The app has a hidden way to clear its caches: go to the Settings tab and tap 7 times in rapid succession on the version number. A "Testing" item will appear and you'll be able to wipe the caches there. (Any options available under "Testing" are officially not supported and are strictly for QA purposes only.)

4. The bottom right of the window is where you specify how you want to rewrite the response. It's also possible to rewrite the requests the app sends out. The possibilities here are many. If for example you want to simulate a 500 server error, click on "Add" and enable:

• Response Status --> Replace with "500 Internal Server Error"

• Body for Response --> Replace with any plain text you want

At this point requests to that URL should fail and Charles should show it in its UI:

Charles allows to rewrite requests and responses in pretty much whatever way you want. For example, to verify how the app behavior changes in relation to caching, you could modify the cache control headers in the response. Or you could add/remove a query param from the request to see how the server responds in real time. The possibilities are endless!