test(internal/librarian): fix validation test (#1747)

Also put some more details in the error for debugging.

Author: codyoss

internal/librarian/init.go

@@ -55,7 +55,7 @@ type initRunner struct {
 
 func newInitRunner(cfg *config.Config) (*initRunner, error) {
 	if ok, err := cfg.IsValid(); !ok || err != nil {
-		return nil, fmt.Errorf("invalid config: %+v", cfg)
+		return nil, fmt.Errorf("invalid config: %w", err)
 	}
 
 	return &initRunner{

internal/librarian/init_test.go

@@ -31,7 +31,9 @@ func TestNewInitRunner(t *testing.T) {
 	}{
 		{
 			name: "valid config",
-			cfg:  &config.Config{},
+			cfg: &config.Config{
+				Repo: "/tmp/repo",
+			},
 		},
 		{
 			name: "invalid config",
@@ -57,7 +59,7 @@ func TestNewInitRunner(t *testing.T) {
 				return
 			}
 			if err != nil {
-				t.Errorf("newInitRunner() got nil runner, want non-nil")
+				t.Errorf("newInitRunner() = %v, want nil", err)
 			}
 		})
 	}