add test code for UnmarshalChartfile

pkg/chartutil/chartfile.go

@@ -35,6 +35,9 @@ const ApiVersionV1 = "v1"
 
 // UnmarshalChartfile takes raw Chart.yaml data and unmarshals it.
 func UnmarshalChartfile(data []byte) (*chart.Metadata, error) {
+	if len(data) == 0 {
+		return nil, nil
+	}
 	y := &chart.Metadata{}
 	err := yaml.Unmarshal(data, y)
 	if err != nil {

pkg/chartutil/chartfile_test.go

@@ -24,6 +24,16 @@ import (
 
 const testfile = "testdata/chartfiletest.yaml"
 
+func TestUnmarshalChartfile(t *testing.T) {
+	metadata, err := UnmarshalChartfile([]byte{})
+	if err != nil {
+		t.Error(err)
+	}
+	if err == nil && metadata != nil {
+		t.Errorf("Want nil, but got %t", metadata)
+	}
+}
+
 func TestLoadChartfile(t *testing.T) {
 	f, err := LoadChartfile(testfile)
 	if err != nil {