TransactionCoordinatorMetricsTest::setUp() sets a MockTickSource on the service context after calling TransactionCoordinatorTestBase::setUp(). This sets up the TransactionCoordinatorTestFixture, which begins the WaitForMajorityService, which spawns a thread that creates operation contexts, which accesses the service context's tick source. The tick source isn't protected by a mutex, so this is a data race. Setting the mock tick source before setting up the WaitForMajorityService should avoid this.