Flutter Widget and Integration Tests — some Surprises about Timeouts and Durations

I’ve been working on a big Flutter project for half a year now. One of my tasks is writing integration tests. In this article I summarize what I have learned about timouts.

You will learn:

• how to fail early when pumpAndSettle() waits on endless running animations.
• how to set the default timeout for all widgetTests.
• some surprises of time and size when running widgetTests.

Preparation of a Tiny Project

I modified the standard counter app for a little experiment:

• I removed the floating action button and replaced it with a timer which increases the _counter every second.
• I added an endless running CircularProgressIndicator.
• I figured out the size of the widget using context.findRenderObject().

Here I start the timer in initState():

The build-method looks like this:

First it gets the size of the widget. When running a widget test the size is printed to the console, an integration test will also show the size on the screen. The _counter value is displayed and below this a Progressindicator will show up forever.

Here is a screenshot of this tiny test app running on an android emulator:

The counter will run until the app is closed — always displaying the animating progress indicator. Note the size of the widget. That’s the real pixel size of the Pixel 2…