Some of the language used in the sharding suites linked to the balancer and random migrations can be confusing. For examples:

• Both the sharding_jscore_passthrough and the sharding_jscore_passthrough_with_balancer suites actually enable the balancer, as reported by the balancerStatus command.
  • The actual difference is that the *_with_balancer suite enables random migrations, while the regular one won't.
• Similarly, the TestData.runningWithBalancer variable and assumes_balancer_off tag are not used by suites that run with the balancer enabled (such as sharding_jscore_passthrough)
  • Rather, it is used by suites that do random migrations.

Revise those terms with unambiguous ones, for example:

• Rename sharding_jscore_passthrough_with_balancer to sharding_jscore_passthrough_with_random_migrations
• Rename TestData.runningWithBalancer to TestData.randomMigrationsEnabled
• Rename assumes_balancer_off to assumes_no_random_migrations