A computer program product for testing a coupling facility of a computing environment, said coupling facility being coupled to one or more processor images of the computing environment and being a shareable facility having storage and processing capabilities and executing coupling facility control code, said computer program product comprising: a computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: receiving by the coupling facility a start operator message command via a send message command, the start operator message command including an operator message command from a source remote from the coupling facility, the source comprising a processor image, the processor image comprising one of: a logical partition having central processor resources and capable of executing an operating system, and the coupling facility being within another logical partition having central processor resources and executing the coupling facility control code; or a stand-alone machine separate from the coupling facility, and the operator message command having an operator message token associated therewith to be stored in a selected buffer of the coupling facility and used to identify the selected buffer once the operator message token is stored in the selected buffer, the selected buffer comprising a token field for storing the operator message token, the operator message command to specify, by the source remote from the coupling facility, an action to be taken on the coupling facility to test whether the coupling facility is behaving as expected pursuant to the action; generating, by the coupling facility based on receiving the start operator message command, a response to the start operator message command and forwarding the response to the start operator message command back to the source remote from the coupling facility; processing by the coupling facility the operator message command to perform the action on the coupling facility to test whether the coupling facility is behaving as expected pursuant to the action; providing by the coupling facility a response to the operator message command; receiving, by the coupling facility from another send message command, a read operator message command generated based on the response to the start operator message command indicating that processing of the operator message command has started, the read operator message command requesting a read of the selected buffer storing the operator message token to obtain the response to the operator message command; returning, by the coupling facility, a response code based on receiving the read operator message command; reading, based on the response code indicating the response to the operator message command is available, the selected buffer to obtain the response to the operator message command; and analyzing the response to the operator message command to determine the effect of the action on the coupling facility. receiving by the coupling facility a start operator message command via a send message command, the start operator message command including an operator message command from a source remote from the coupling facility, the source comprising a processor image, the processor image comprising one of: a logical partition having central processor resources and capable of executing an operating system, and the coupling facility being within another logical partition having central processor resources and executing the coupling facility control code; or a stand-alone machine separate from the coupling facility, and the operator message command having an operator message token associated therewith to be stored in a selected buffer of the coupling facility and used to identify the selected buffer once the operator message token is stored in the selected buffer, the selected buffer comprising a token field for storing the operator message token, the operator message command to specify, by the source remote from the coupling facility, an action to be taken on the coupling facility to test whether the coupling facility is behaving as expected pursuant to the action; generating, by the coupling facility based on receiving the start operator message command, a response to the start operator message command and forwarding the response to the start operator message command back to the source remote from the coupling facility; processing by the coupling facility the operator message command to perform the action on the coupling facility to test whether the coupling facility is behaving as expected pursuant to the action; providing by the coupling facility a response to the operator message command; receiving, by the coupling facility from another send message command, a read operator message command generated based on the response to the start operator message command indicating that processing of the operator message command has started, the read operator message command requesting a read of the selected buffer storing the operator message token to obtain the response to the operator message command; returning, by the coupling facility, a response code based on receiving the read operator message command; reading, based on the response code indicating the response to the operator message command is available, the selected buffer to obtain the response to the operator message command; and analyzing the response to the operator message command to determine the effect of the action on the coupling facility.