This is perhaps not important.
We have a situation where we have TestChild extending TestParent, which extends TestCase. TestParent *used to * have a setup() method at some stage, and TestChild called super.setup() in its own setup(). All good.
Then at some stage setup() was removed from TestParent, so TestChild's super.setup() was calling TestCase's setup(). MXUNit has a setup() in TestCase. TestBox does not. Therefore our tests error.
But, as I said, this is more being caught out by sloppy code on our end, but figured I'd let you know anyhow.