Fix: stack down shows fake error (#528)

* Fix: stack down shows fake error

* Add unit tests

* Fix: licenser

Author: mtojek

internal/install/application_configuration.go

@@ -17,7 +17,9 @@ import (
 	"github.com/elastic/elastic-package/internal/logger"
 )
 
-var elasticAgentCompleteFirstSupportedVersion = semver.MustParse("7.15.0-SNAPSHOT")
+const stackVersion715 = "7.15.0-SNAPSHOT"
+
+var elasticAgentCompleteFirstSupportedVersion = semver.MustParse(stackVersion715)
 
 // ApplicationConfiguration represents the configuration of the elastic-package.
 type ApplicationConfiguration struct {
@@ -73,6 +75,10 @@ func (ac *ApplicationConfiguration) StackImageRefs(version string) ImageRefs {
 // selectElasticAgentImageName function returns the appropriate image name for Elastic-Agent depending on the stack version.
 // This is mandatory as "elastic-agent-complete" is available since 7.15.0-SNAPSHOT.
 func selectElasticAgentImageName(version string) string {
+	if version == "" { // as version is optional and can be empty
+		return elasticAgentImageName
+	}
+
 	v, err := semver.NewVersion(version)
 	if err != nil {
 		logger.Errorf("stack version not in semver format (value: %s): %v", v, err)

internal/install/application_configuration_test.go

@@ -0,0 +1,35 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package install
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSelectElasticAgentImageName_NoVersion(t *testing.T) {
+	var version string
+	selected := selectElasticAgentImageName(version)
+	assert.Equal(t, selected, elasticAgentImageName)
+}
+
+func TestSelectElasticAgentImageName_OlderStack(t *testing.T) {
+	version := "7.14.99-SNAPSHOT"
+	selected := selectElasticAgentImageName(version)
+	assert.Equal(t, selected, elasticAgentImageName)
+}
+
+func TestSelectElasticAgentImageName_FirstStackWithCompleteAgent(t *testing.T) {
+	version := stackVersion715
+	selected := selectElasticAgentImageName(version)
+	assert.Equal(t, selected, elasticAgentCompleteImageName)
+}
+
+func TestSelectElasticAgentImageName_NextStackWithAgentComplete(t *testing.T) {
+	version := "7.16.0-SNAPSHOT"
+	selected := selectElasticAgentImageName(version)
+	assert.Equal(t, selected, elasticAgentCompleteImageName)
+}