koobas.hobune.stream
How to write Unity tests for a CustomPropertyDrawer?
Consider the below PropertyDrawer:
[CustomPropertyDrawer(typeof(TagAttribute))]
class TagPropertyDrawer: PropertyDrawer
{
public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
{
property.stringValue = EditorGUI.TagField(position, label, property.stringValue);
}
}
Unity recognizes the [CustomPropertyDrawer(typeof(TagAttribute))] and creates a [Tag] which I have used on the tagAttribute field below:
public class Demo : MonoBehaviour
{
[Tag] public string tagAttribute;
}
This instructs the Unity Inspector to use my TagPropertyDrawer.OnGUI for drawing the tagAttribute field, resulting in a Tag dropdown instead of a plain string textbox as shown below: 
While this works just fine, I am not sure how do I write a Unity test case that ensures that a TagField is rendered when a [Tag] property is used on a component's field? Is it even possible to write such a test?
I could just try and call the TagPropertyDrawer.OnGUI function directly, but while that can test that the EditorGUI.TagField is called when OnGUI is called, it won't test that OnGUI is called in the first place when the component is rendered.
