In my build (based on Ostro OS), /usr/lib/dbus-test/ptest/test/test-dbus was just the libtool wrapper script and the actual binary wasn't packaged. Then running the wrapper on the target failed (no compiler, no source code). That the binary was missing seemed specific to my build. Either way, dbus-test should install the actual binary, not some libtool wrapper. Ross also suggested that a QA check should be written to detect such problems.
Patch on the list.
Fixed in oe-core 6ebe903f1aed3002ba43419a312c84bfbd1288dd.
Fixed in oe-core a4b5076b2c06cafff0ce764955d0aa7c334c7a8e.