In an evergreen patch for an unrelated feature, I got a failure on OSX 64 nossl in the monogc-socket check_closed test. It seems like this test failed on the base patch as well. Here's the log for the base patch:

https://evergreen.mongodb.com/task/mongo_c_driver_os_x_1010_64_nossl_integration_test_3.0_replica_set_no_auth_cd4c2b4f636baca5719614fe9e82ff37a336090b_16_08_04_14_02_22

Here's the failure:

 [2016/08/05 14:16:21.892] Assertion failed: (closed == true), function socket_test_client, file tests/test-mongoc-socket.c, line 153.

It looks like none of the commits since then have been to address this bug, so maybe it still exists, but just isn't being "triggered."

Forgive me if this is a duplicate.