[SUREFIRE-1447] get an (estimated?) test count

**[Allen Wittenauer](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=aw)** opened **[SUREFIRE-1447](https://issues.apache.org/jira/browse/SUREFIRE-1447?redirect=false)** and commented

It would be beneficial if there were a way to ask surefire how many tests it expects to run. This feature would act as a way to double check the quality of the run. For example, we've noticed that when mvn test is run under duress that causes surefire itself to crash, some tests are never logged. Being able to count how many tests are missing would provide some great insight.

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**Issue Links:**
- [YETUS-587](https://issues.apache.org/jira/browse/YETUS-587) Report if junit drops a significant amount of tests

Start by reading SUREFIRE-1447 and the linked YETUS-587 discussion, then inspect how Surefire reports tests during an mvn test run. Clarify whether the expected count can be estimated reliably and what output should expose missing tests; the work is done when that behavior and its limitations are specified and tested.

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