graph/db: refactor to make postgres fixtures re-usable

In preparation for tests where we will want to spin up SQL DBs many
times, we do some refactoring so that it is easy to re-use postgres
fixtures since those are expensive to spin up.

graph/db/test_sqlite.go

@@ -6,12 +6,45 @@ import (
 	"database/sql"
 	"testing"
 
+	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/lightningnetwork/lnd/sqldb"
+	"github.com/stretchr/testify/require"
 )
 
+// NewTestDB is a helper function that creates a SQLStore backed by a SQL
+// database for testing.
+func NewTestDB(t testing.TB) V1Store {
+	return NewTestDBWithFixture(t, nil)
+}
+
+// NewTestDBFixture is a no-op for the sqlite build.
+func NewTestDBFixture(_ *testing.T) *sqldb.TestPgFixture {
+	return nil
+}
+
+// NewTestDBWithFixture is a helper function that creates a SQLStore backed by a
+// SQL database for testing.
+func NewTestDBWithFixture(t testing.TB, _ *sqldb.TestPgFixture) V1Store {
+	store, err := NewSQLStore(
+		&SQLStoreConfig{
+			ChainHash: *chaincfg.MainNetParams.GenesisHash,
+		}, newBatchQuerier(t),
+	)
+	require.NoError(t, err)
+	return store
+}
+
 // newBatchQuerier creates a new BatchedSQLQueries instance for testing
 // using a SQLite database.
 func newBatchQuerier(t testing.TB) BatchedSQLQueries {
+	return newBatchQuerierWithFixture(t, nil)
+}
+
+// newBatchQuerierWithFixture creates a new BatchedSQLQueries instance for
+// testing using a SQLite database.
+func newBatchQuerierWithFixture(t testing.TB,
+	_ *sqldb.TestPgFixture) BatchedSQLQueries {
+
 	db := sqldb.NewTestSqliteDB(t).BaseDB
 
 	return sqldb.NewTransactionExecutor(