Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @irfansharif, @knz, @tbg, and @TheSamHuang)

pkg/server/migration_test.go, line 101 at r1 (raw file):

}

func TestBumpClusterVersion(t *testing.T) {

// TestBumpClusterVersion verifies that the BumpClusterVersion RPC correctly
// persists the cluster version to disk and updates the active in-memory version.

pkg/server/migration_test.go, line 138 at r1 (raw file):

	ctx := context.Background()
	for _, test := range tests {

use subtests here, then you can also defer the stopper.Stop() call. Right now we're leaking goroutines if the test fails.

pkg/server/migration_test.go, line 170 at r1 (raw file):

			ClusterVersion: &test.bumpClusterVersion,
		}
		if _, err := migrationServer.BumpClusterVersion(ctx, req); err != nil {

Would you mind updating WriteClusterVersion (not in the diff) to take a raw engine, and add a comment that this ensures that the write is synched. Right now it takes a ReadWriter and is thus subject to not syncing automatically when called with, e.g., a batch.
Or, we make them take an explicit batch, deal with all the fallout, and then make sure to Commit(true /* sync */) that batch.

Doesn't have to be in this PR, probably should not.

pkg/server/migration_test.go, line 174 at r1 (raw file):

		}

		// Check to see our post-bump active cluster version is what we expect.

see if our