Make test InsertRetryRemoveOther less flaky

Summary: The SingleMockThreadScheduler has a background thread that runs jobs. So it's possible for our assertion on number of jobs done to be racy and fail the test. The changes now will explicitly wait until all jobs have completed in the scheduler before checking, which eliminates the race.

Reviewed By: haowu14

Differential Revision: D47580097

fbshipit-source-id: adc3474d384e9fc3755371c584d3f665305a279e

Author: Jimmy Lu

cachelib/navy/driver/tests/DriverTest.cpp

@@ -466,12 +466,18 @@ TEST(Driver, InsertRetryRemoveOther) {
   auto driver = std::make_unique<Driver>(std::move(config));
 
   EXPECT_EQ(Status::Ok, driver->insert(makeHK("key"), largeValue.view()));
+
+  // Flush the scheduler first
+  exPtr->finish();
   EXPECT_EQ(exPtr->getRescheduleCount(), 0);
   EXPECT_EQ(exPtr->getDoneCount(), 1);
 
   // The returned status code is Ok because it's not rejected by admission test.
   // Under the hood, the schedule went through one reschedule and one succeed.
   EXPECT_EQ(Status::Ok, driver->insert(makeHK("key"), smallValue.view()));
+
+  // Flush the scheduler first
+  exPtr->finish();
   EXPECT_EQ(exPtr->getRescheduleCount(), 1);
   EXPECT_EQ(exPtr->getDoneCount(), 2);