The text editing test APIs (e.g. performTextInput) currently take a parameter called alreadyHasFocus, and when it's false (the default) they click the middle of the text field before attempting to perform input. I find that for any non-trivial tests involving a TextField I almost always have to explicitly set this to true, because clicking in the middle of the text field puts the cursor in an essentially arbitrary position.

I think a better API would fetch the current state of the node and only focus it if isn't already focused (and probably set the selection to something well defined, like the end of the text). If it's important for the text field to already be focused the writer of the test can use assertIsFocused().