Presently, the major_version_upgrade.js test only calls setFeatureCompatibilityVersion to ensure a featureCompatibilityVersion document exists before upgrade to 3.6, since as of 3.6 mongod fails to startup without this document. This test should be modified to always set the featureCompatibilityVersion to the version that corresponds to the current binary version (i.e., 3.6 mongod should set the fCV to 3.6) before upgrading to the following binary version. This is only necessary for versions 3.4 to latest, since the featureCompatibilityVersion was introduced in 3.4.