Add unit tests for script stage

Refs: #406

internal/osbuild/script_stage_test.go

@@ -0,0 +1,24 @@
+package osbuild
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewScriptStageOptions(t *testing.T) {
+	expectedOptions := &ScriptStageOptions{
+		Script: "/root/test.sh",
+	}
+	actualOptions := NewScriptStageOptions("/root/test.sh")
+	assert.Equal(t, expectedOptions, actualOptions)
+}
+
+func TestNewScriptStage(t *testing.T) {
+	expectedStage := &Stage{
+		Name:    "org.osbuild.script",
+		Options: &ScriptStageOptions{},
+	}
+	actualStage := NewScriptStage(&ScriptStageOptions{})
+	assert.Equal(t, expectedStage, actualStage)
+}