Chore/improve coverage

[Ascenio]

✨ What kind of change does this PR introduce? (Bug fix, feature, docs update...)

This PR adds new tests, reaching code paths not previously covered as pointed by a coverage report.

⤵️ What is the current behavior?

All tests are currently passing and result in 64.8% coverage.

🆕 What is the new behavior (if this is a feature change)?

All tests are currently passing and result in 92.9% coverage.

💥 Does this PR introduce a breaking change?

No. It does not change any lib/ file.

🐛 Recommendations for testing

If you want to see the coverage report I mentioned before you could use genhtml tool. Just run the following:

flutter test --coverage && genhtml coverage/lcov.info -o coverage/report && open coverage/report/index.html

📝 Links to relevant issues/docs

None.

🤔 Checklist before submitting

• I made sure all projects build.
• I updated CHANGELOG.md to add a description of the change.
• I updated the relevant documentation.
• I updated the relevant code example.
• I rebased onto current master.

[chunhtai]

Since this package has been moved to https://github.com/flutter/packages/tree/main/packages/go_router

Can you create a pull request against the flutter/packages instead?