accounts: update NewTestDB func to return Store

In preparation for upcoming migration tests from a kvdb to an SQL store,
this commit updates the NewTestDB function to return the Store interface
rather than a concrete store implementation.

This change ensures that migration tests can call NewTestDB under any
build tag while receiving a consistent return type.

accounts/test_kvdb.go

@@ -15,14 +15,14 @@ import (
 var ErrDBClosed = errors.New("database not open")
 
 // NewTestDB is a helper function that creates an BBolt database for testing.
-func NewTestDB(t *testing.T, clock clock.Clock) *BoltStore {
+func NewTestDB(t *testing.T, clock clock.Clock) Store {
 	return NewTestDBFromPath(t, t.TempDir(), clock)
 }
 
 // NewTestDBFromPath is a helper function that creates a new BoltStore with a
 // connection to an existing BBolt database for testing.
 func NewTestDBFromPath(t *testing.T, dbPath string,
-	clock clock.Clock) *BoltStore {
+	clock clock.Clock) Store {
 
 	store, err := NewBoltStore(dbPath, DBFilename, clock)
 	require.NoError(t, err)

accounts/test_postgres.go

@@ -15,14 +15,14 @@ import (
 var ErrDBClosed = errors.New("database is closed")
 
 // NewTestDB is a helper function that creates an SQLStore database for testing.
-func NewTestDB(t *testing.T, clock clock.Clock) *SQLStore {
+func NewTestDB(t *testing.T, clock clock.Clock) Store {
 	return NewSQLStore(db.NewTestPostgresDB(t).BaseDB, clock)
 }
 
 // NewTestDBFromPath is a helper function that creates a new SQLStore with a
 // connection to an existing postgres database for testing.
 func NewTestDBFromPath(t *testing.T, dbPath string,
-	clock clock.Clock) *SQLStore {
+	clock clock.Clock) Store {
 
 	return NewSQLStore(db.NewTestPostgresDB(t).BaseDB, clock)
 }

accounts/test_sqlite.go

@@ -15,14 +15,14 @@ import (
 var ErrDBClosed = errors.New("database is closed")
 
 // NewTestDB is a helper function that creates an SQLStore database for testing.
-func NewTestDB(t *testing.T, clock clock.Clock) *SQLStore {
+func NewTestDB(t *testing.T, clock clock.Clock) Store {
 	return NewSQLStore(db.NewTestSqliteDB(t).BaseDB, clock)
 }
 
 // NewTestDBFromPath is a helper function that creates a new SQLStore with a
 // connection to an existing SQL database for testing.
 func NewTestDBFromPath(t *testing.T, dbPath string,
-	clock clock.Clock) *SQLStore {
+	clock clock.Clock) Store {
 
 	return NewSQLStore(
 		db.NewTestSqliteDbHandleFromPath(t, dbPath).BaseDB, clock,