A system and method may generate executable block diagrams having blocks that run in accordance with message-based execution semantics. A message may include an input data payload that does not change over time, and the message may persist for only a determined time interval during execution of block diagram. A verification engine may provide one or more tools for evaluating and verifying operation of message-based blocks. The verification engine may support one or more verification blocks that may be added to the block diagram and associated with the diagram's message-based blocks. The verification blocks may capture and present messages exchanged among the message-based blocks. The verification blocks may also specify an expected interaction of messages, and determine whether the actual messages are equivalent to the expected interaction.
