Testing information for testing a distributed application is included in messages that are also used by the distributed application to transport data. A test initiator causes test information to be inserted in the header portion or a header element of a message that is being transported across a distributed system. The test initiator may insert test information directly or may cause a message router that receives the message to merge test information into the message. The message, which now includes distributed application data and test information, is routed to a message recipient. The message recipient accesses the message to identify tests that are to be performed at the message recipient. The message recipient performs at least one of the identified tests. Inserting and routing test information, as well as, performing tests may be done in a transport-independent manner.