This is an umbrella issue for all kinds of unit-test improvements. Unit-tests in this repository are significantly outdated, and need a revamp. For example:

• raft_test.go
• rawnode_test.go

Examples of things to fix/improve:

• Fix incorrect initialization of nodes, make a standard way to do this. Some tests change RawNode / raft structs arbitrarily, which breaks internal invariants and makes tests prone to false failures on any change. This necessitates PR authors to spend time debugging and fixing incorrect tests.
• Eliminate boilerplate.
  • For example, all assertions should use require/assert packages. Revisit tests #146 (comment)
• Introduce helpers, to eliminate more boilerplate.
  • For example, entry slices don't need to be copy-pasted many times, and can be generated with a simple function. tests: add helpers for generating entry slices #147
• Introduce test-only invariant checks that happen transparently in all tests. An example invariant: r.Term >= r.raftLog.lastTerm(). Tests that manipulate RawNode structs directly may accidentally break invariants, and end up testing arbitrary behaviour rather than real one.