This is just a start and there are 8 passing tests. The two undefined.u0/u1 tests are commented out as they are currently failing when I don't feel they should.
$ zig test ux-semantics.zig
Test 1/8 assignment.u0...OK
Test 2/8 assignment.u1...OK
Test 3/8 sizeof.u0...OK
Test 4/8 sizeof.u1...OK
Test 5/8 intCast.u0...OK
Test 6/8 intCast.u1...OK
Test 7/8 address.u0...OK
Test 8/8 address.u1...OK
All tests passed.