Observed in OpenSSL build on Windows:
[2017/01/15 19:01:35.027] Begin /Async/ismaster_ssl [2017/01/15 19:01:43.408] error: TLS handshake failed: error:00000000:lib(0):func(0):reason(0) [2017/01/15 19:01:43.408] FAIL [2017/01/15 19:01:43.408] [2017/01/15 19:01:43.408] Assert Failure: 2 == 1 [2017/01/15 19:01:43.408] tests\test-mongoc-async.c:34 test_ismaster_helper()
I'm disabling the test on Windows with OpenSSL for now in order to get our test suite reliable.