fix(review): harden payment, oauth, and migration paths

backend/internal/payment/wire_test.go

@@ -0,0 +1,62 @@
+package payment
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+)
+
+func TestProvideEncryptionKeySkipsAutoGeneratedTotpKey(t *testing.T) {
+	t.Parallel()
+
+	cfg := &config.Config{
+		Totp: config.TotpConfig{
+			EncryptionKey:           strings.Repeat("a", 64),
+			EncryptionKeyConfigured: false,
+		},
+	}
+
+	key, err := ProvideEncryptionKey(cfg)
+	if err != nil {
+		t.Fatalf("ProvideEncryptionKey returned error: %v", err)
+	}
+	if len(key) != 0 {
+		t.Fatalf("encryption key len = %d, want 0", len(key))
+	}
+}
+
+func TestProvideEncryptionKeyUsesConfiguredTotpKey(t *testing.T) {
+	t.Parallel()
+
+	cfg := &config.Config{
+		Totp: config.TotpConfig{
+			EncryptionKey:           "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
+			EncryptionKeyConfigured: true,
+		},
+	}
+
+	key, err := ProvideEncryptionKey(cfg)
+	if err != nil {
+		t.Fatalf("ProvideEncryptionKey returned error: %v", err)
+	}
+	if len(key) != 32 {
+		t.Fatalf("encryption key len = %d, want 32", len(key))
+	}
+}
+
+func TestProvideEncryptionKeyRejectsConfiguredInvalidLength(t *testing.T) {
+	t.Parallel()
+
+	cfg := &config.Config{
+		Totp: config.TotpConfig{
+			EncryptionKey:           "abcd",
+			EncryptionKeyConfigured: true,
+		},
+	}
+
+	_, err := ProvideEncryptionKey(cfg)
+	if err == nil {
+		t.Fatal("expected error for invalid key length")
+	}
+}