Often times it's difficult to know which tests have failed when flutter test runs. For example: https://cirrus-ci.com/task/6163921269686272?logs=main#L3250

The report at the end just says:

07:49 +6413 ~14 -5: Some tests failed.

Then you have to scroll up looking for the failure which isn't always easy to find and if you search for "fail" in the text many tests print out that text while not failing.

The report at the end should list the tests that failed.