fix: prevent panic when ChartDownloader.getOciURI

needs to lookup tags because no version is provided
but no RegistryClient is provided

Add tests for oci registries

Signed-off-by: Carlos Sanchez <carlos@apache.org>

pkg/downloader/chart_downloader_test.go

@@ -16,6 +16,7 @@ limitations under the License.
 package downloader
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"testing"
@@ -37,6 +38,8 @@ const (
 )
 
 func TestResolveChartRef(t *testing.T) {
+	ociRegistryUrl := "localhost:5000"
+
 	tests := []struct {
 		name, ref, expect, version string
 		fail                       bool
@@ -61,6 +64,13 @@ func TestResolveChartRef(t *testing.T) {
 		{name: "no repository", ref: "oci://", fail: true},
 		{name: "oci ref", ref: "oci://example.com/helm-charts/nginx", version: "15.4.2", expect: "oci://example.com/helm-charts/nginx:15.4.2"},
 		{name: "oci ref with sha256 and version mismatch", ref: "oci://example.com/install/by/sha:0.1.1@sha256:d234555386402a5867ef0169fefe5486858b6d8d209eaf32fd26d29b16807fd6", version: "0.1.2", fail: true},
+
+		// OCI tests
+		{name: "OCI with version", ref: fmt.Sprintf("oci://%s/u/ocitestuser/oci-dependent-chart", ociRegistryUrl), version: "0.1.0",
+			expect: fmt.Sprintf("oci://%s/u/ocitestuser/oci-dependent-chart:0.1.0", ociRegistryUrl)},
+		{name: "OCI without version fails without registry client", ref: fmt.Sprintf("oci://%s/u/ocitestuser/oci-dependent-chart", ociRegistryUrl),
+			expect: fmt.Sprintf("oci://%s/u/ocitestuser/oci-dependent-chart:0.1.0", ociRegistryUrl), fail: true},
+		{name: "not found", ref: "oci://localhost:9999/nosuchthing/invalid-1.2.3", fail: true},
 	}
 
 	registryClient, err := registry.NewClient()