Add some more contextual information to the README

sdktest/README.md

@@ -1,11 +1,12 @@
 # sdktest
 
-**sdktest** is a tool for testing our SDK in all kinds of scenario's, end-to-end, in different browsers.
+**sdktest** is a tool for testing our SDK in all kinds of scenarios, end-to-end, in different browsers.
 
 **sdktest** is not designed to be beautiful, fast or elegant, it only has to do its job well.
 
-
 ## Getting Started
+
+* Ensure you've built the SDK (in the parent folder, `npm run build`)
 * Install Go for your device (`brew install go`)
 * Create a config file in the root of this folder called `sdktest.yaml`, [`sdktest.example.yaml`](./sdktest.example.yaml) should provide a good starting point.
 * Run `go run main.go server` and point your browser at [`localhost:8912`](http://localhost:8912).
@@ -19,3 +20,10 @@ go run main.go autotest
 # Or with serve, to keep the server alive too for headful debugging.
 go run main.go autotest --serve
 ```
+
+## A note on widget interactivity
+
+By default, widgets require the web user to click the checkbox in order to complete. This means
+that the test cases that expect a widget to complete will---under the default conditions---fail with a `TimeoutError` unless you manually click the checkbox. This is expected behavior, and you can make the tests pass by clicking the checkboxes.
+
+There is a way to make the tests pass without requiring manual clicking, and it involves using a sitekey for an application whose widget mode is set to `noninteractive`. Widgets with that mode can complete without any additional interaction from the web user.