test: replace mocks with mockgen mocks

  * Replaced table-driven tests with direct mock setup for single-case tests to improve readability and reduce unnecessary indirection.
  * Used GoMock idioms (.Return, .Times, .After) for retry logic to make mock expectations clearer and more robust.
  * Added comments to clarify mock and test intent, aiding future maintainers.
  * Ensured all retry, error, and success paths are covered to match production logic and prevent regressions.
  * Maintained test and code coverage at the level of the main branch to ensure no loss in quality.

Author: bernielomax

internal/cmd/images/manifest_cmd_test.go

@@ -6,19 +6,8 @@ import (
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
-	helmlib "github.com/mittwald/go-helm-client"
-
-	"github.com/airbytehq/abctl/internal/helm"
 )
 
-func getHelmTestClient(t *testing.T) helm.Client {
-	client, err := helmlib.New(nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	return client
-}
-
 func TestManifestCmd(t *testing.T) {
 	cmd := ManifestCmd{
 		ChartVersion: "1.1.0",