C++ Unit Test (gtest) fail due to exception with description "Function xxxxx is unimplemented" thrown in test body

I'm writing unit tests using googletest for my C++ project, which makes use of Thrift to communicate between C++ (server) and Python (client). The method of which I'm writing unit test has been manually tested on Python client and works fine. However, when I tried to write unit test for it, the test failed due to the below reason:

✗ xxxxxx/xxxxxx/server:ServerTests - TestClass.testName 0.974s (FAIL)
I1001 09:11:53.086431 2200572 ThreadSchedulerImpl.cpp:321] Starting ThreadSchedulerImpl with 128 max working threads
I1001 09:11:53.086674 2200572 ThreadSchedulerImpl.cpp:350] Smart scheduling algorithm is turned on unknown file: Failure
C++ exception with description "Function xxxxx is unimplemented" thrown in the test body.

Any idea what this might be the reason for this?