This seems to work perfectly fine:
and when I created a new project with e
Where / How did you add the image in your project ?
The second syntax (without the path) should be ok. You don't even have to specify .png if that's the file format (but you need to if it something else : .jpg, .jpeg, ...
You might want to check that your asset is "checked" for the target membership. On the right side (Utilities) > File Inspector > Target Membership : check your target (not the tests one if you don't have any tests).