Python test runner regrtest has many options to select tests: -u (resources), -m and --matchfile, -x (exclude), etc. Sometimes, I do a mistake and I run 0 test, but I still get a success.

Maybe regrtest should be modified to fail with an error when no test is run? At least, it would help to understand my mistake if regrtest could emit a warning in such case.

Example:
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$ ./python  -W error  -m test test_asyncio -m test_set_default_executor_deprecation_warnings 
Run tests sequentially
0:00:00 load avg: 0.27 [1/1] test_asyncio

== Tests result: SUCCESS ==

1 test OK.

Total duration: 266 ms
Tests result: SUCCESS
---

Success ok, but is there a typo in the test method?

Another example:
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$ ./python  -W error  -m test test_asyncio -m test_no_such_test -v
== CPython 3.8.0a0 (heads/pr/8533:50c0499950, Jul 30 2018, 12:41:53) [GCC 8.1.1 20180712 (Red Hat 8.1.1-5)]
== Linux-4.17.6-200.fc28.x86_64-x86_64-with-glibc2.26 little-endian
== cwd: /home/vstinner/prog/python/master/build/test_python_5505
== CPU count: 8
== encodings: locale=UTF-8, FS=utf-8
Run tests sequentially
0:00:00 load avg: 0.31 [1/1] test_asyncio

----------------------------------------------------------------------
Ran 0 tests in 0.001s

OK

== Tests result: SUCCESS ==

1 test OK.

Total duration: 318 ms
Tests result: SUCCESS
---

Success but no test have been executed. It's not obvious at all without the verbose mode:
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$ ./python  -W error  -m test test_asyncio -m test_no_such_test 
Run tests sequentially
0:00:00 load avg: 0.31 [1/1] test_asyncio

== Tests result: SUCCESS ==

1 test OK.

Total duration: 260 ms
Tests result: SUCCESS
---