Unit tests that verify results of FieldAvailability or ProvidedSortSet are using ASSERT_TRUE with ==, rather than ASSERT_EQ, this is due to those types not having << operator for ostream, so that the values can be printed in case of mismatch.

Example: 

https://github.com/10gen/mongo/blob/26bcd0f788184402ecefdc1221faf13a1f9b6e47/src/mongo/db/query/query_solution_test.cpp

We should add those operators and change ASSERT_TRUE to ASSERT_EQ where possibl to improve test debuggability.