Assume your current directory is the chat folder. To run mdtest for this chat app, first plugin two Android/iOS devices and just run

mdtest auto --format tap \
            --coverage \
            --save-report-data chat-test-report.json \
            --groupby os-version \
            --spec mdtest/chat.spec \

The above command tells mdtest to run in auto mode, print test output in TAP format, collect coverage information, save report data to chat-test-report.json, group all devices by their OS version, use the test spec located at mdtest/chat.spec and run the test script mdtest/chat_test.dart.

The above command will produce the coverage information in coverage/cov_auto_01.lcov, you can generate the code coverage report by running

mdtest generate --report-type coverage \
                --load-report-data coverage/cov_auto_01.lcov \
                --lib lib \
                --output coverage_report

and mdtest will invoke lcov to generate a coverage report under coverage_report folder.

To generate a test report, you can run

mdtest generate --report-type test \
                --load-report-data chat-test-report.json \
                --output test_report

and mdtest will generate the test report using the data in chat-test-report.json and write the HTML report under test_report folder.