Rather than assuming that you know the height of all the items
in a list, or that a particular widget is rendered on all devices,
the scrollUntilVisible() method trepeatedly scrolls through
a list of items until it finds what it’s looking for.

The following code shows how to use the scrollUntilVisible() method
to look through the list for a particular item. This code lives in a
file called test/widget_test.dart.

3. Run the test

Run the test using the following command from the root of the project:

Find widgets

Tap, drag, and enter text