`dcm analyze` false positives

[kenzieschmoll]

@incendial finding some more false positives here. I can file these somewhere else if that is better for you, just let me know.

packages/devtools_app/test/screens/debugger/syntax_highlighter_test.dart (1 issue):
WARNING   This test group does not contain any test cases.
          at packages/devtools_app/test/screens/debugger/syntax_highlighter_test.dart:514:7
          avoid-empty-test-groups : https://dcm.dev/docs/rules/common/avoid-empty-test-groups

[incendial]

Is it possible to mark testSingleSpan with @isTest? The rule cannot find any test invocations and that's why it shows a warning.

I can file these somewhere else if that is better for you,

Having them here is fine 👍