Minor select test database setup simplify

- Use in memory database when amount is not big (`TestTrieDiff`)
- Do not create unneeded `trie` table in `lib/trie`'s `newTestDB`
- `dot/state`: use `t.TempDir()` as data dir directly

dot/state/storage_test.go

@@ -4,7 +4,6 @@
 package state
 
 import (
-	"path/filepath"
 	"testing"
 	"time"
 
@@ -167,10 +166,8 @@ func TestStorage_StoreTrie_NotSyncing(t *testing.T) {
 }
 
 func TestGetStorageChildAndGetStorageFromChild(t *testing.T) {
-	// initialise database using data directory
-	basepath := t.TempDir()
 	db, err := chaindb.NewBadgerDB(&chaindb.Config{
-		DataDir: filepath.Join(basepath, "db"),
+		DataDir: t.TempDir(),
 	})
 	require.NoError(t, err)
 	t.Cleanup(func() {

lib/trie/database_test.go

@@ -21,7 +21,7 @@ func newTestDB(t *testing.T) chaindb.Database {
 		err := database.Close()
 		require.NoError(t, err)
 	})
-	return chaindb.NewTable(database, "trie")
+	return database
 }
 
 func Test_Trie_Store_Load(t *testing.T) {

lib/trie/trie_endtoend_test.go

@@ -267,23 +267,13 @@ func TestDeleteOddKeyLengths(t *testing.T) {
 }
 
 func TestTrieDiff(t *testing.T) {
-	cfg := &chaindb.Config{
-		DataDir: t.TempDir(),
-	}
-
-	db, err := chaindb.NewBadgerDB(cfg)
-	require.NoError(t, err)
-
+	db := newTestDB(t)
 	t.Cleanup(func() {
-		err = db.Close()
+		err := db.Close()
 		require.NoError(t, err)
 	})
 
 	storageDB := chaindb.NewTable(db, "storage")
-	t.Cleanup(func() {
-		err := storageDB.Close()
-		require.NoError(t, err)
-	})
 
 	trie := NewEmptyTrie()
 
@@ -300,7 +290,7 @@ func TestTrieDiff(t *testing.T) {
 	}
 
 	newTrie := trie.Snapshot()
-	err = trie.WriteDirty(storageDB)
+	err := trie.WriteDirty(storageDB)
 	require.NoError(t, err)
 
 	tests = []keyValues{