A few things in these patches.
Firstly, the background changes are some additions & cleanups to MinimapDialogTest.
I've had a go at using Awaitility in response to sonar's nagging instead of Thread.sleep(). As such the topmost patch (6/6) in this series depends on awaitility-3.0.0.jar being added to test/lib/. Obviously it would be dumb of me to include that in my patches - you can do that yourselves.
To be anything other than a fancy Thread.sleep(), Awaitility also needs to be provided with a callback to be able to check whether the expected operation has completed. I had some trouble in doing this for these tests.
In the end I found myself adding a new method, hasOutstandingTasks() to JMapViewer's TileLoader interface. It may be going a bit far, but tile loading is something that could do with a lot more testing across the suite, and this would give us the mechanism to test that asynchronous task "safely". To lessen the impact on any external implementers of TileLoader, I included a default implementation (which raises UnsupportedOperationException) to remove the immediate need to implement it. I realize this belongs to a separate repository so have kept the patch separate (patch 4/6).
This set of changes is browsable at https://github.com/risicle/josm/compare/ae5f93c3afbbf9e295456047081946af80dea8f3...ris-minimapdialogtest-ext
Patches based on top of r13110
In 13112/josm: