miner: get rid of test_backend helper functions

core/txindexer_test.go

@@ -71,9 +71,11 @@ func TestTxIndexer(t *testing.T) {
 	}
 	verify := func(db ethdb.Database, expTail uint64, indexer *txIndexer) {
 		tail := rawdb.ReadTxIndexTail(db)
+		//nolint: staticcheck
 		if tail == nil {
 			t.Fatal("Failed to write tx index tail")
 		}
+		//nolint: staticcheck
 		if *tail != expTail {
 			t.Fatalf("Unexpected tx index tail, want %v, got %d", expTail, *tail)
 		}

core/vm/interpreter.go

@@ -41,10 +41,12 @@ var (
 	ErrNoCurrentTx               = errors.New("no current tx found in interruptCtx")
 )
 
+type InterruptKeyType string
+
 const (
 	// These are keys for the interruptCtx
-	InterruptCtxDelayKey       = "delay"
-	InterruptCtxOpcodeDelayKey = "opcodeDelay"
+	InterruptCtxDelayKey       InterruptKeyType = "delay"
+	InterruptCtxOpcodeDelayKey InterruptKeyType = "opcodeDelay"
 
 	// InterruptedTxCacheSize is size of lru cache for interrupted txs
 	InterruptedTxCacheSize = 90000