In the current tool integration tests, we usually test with a pre-generated source bson file and verify the result. Since the bson file is generated with a specific server version, in all our evergreen tests, we are actually testing from 1 server version to all.

For example, in Mongorestore testing, TestMongorestore will try to restore from bson file 

"testdata/testdirs/db1/c1.bson" to any destination server version. 

1. This is contrary to our assumption that Mongotools should not be used across versions. 
2. This prohibits us from finding issues when a new oplog format is introduced since the source bson file never changes.

I believe introducing E2E tests could solve this issue.