The correct notation is for example:

entry/Activity entry

All the diagrams in PSSM show instead

/entry Activity entry

This is confusing and should get changed.
Also the text in all examples of the UML specification is left justified. It is not mentioned as a requirement, but I think most tools follow this convention. In the PSSM specification the text is centered. I suggest to change it to left justified.
The effect of Transitions is notated with a colon:

/Activity: effect.

I think that should also be consistent. Either remove the colon, or use it with state behaviors as well.
As an additional suggestion: In most cases it is not relevant for the test case, that an activity is called. The string "Activity" could be left out to keep the diagram less cluttered.

The behavioral part of the PSSM semantic model is specified using Java syntax. The subset of Java that is used does not always conform to the mapping rules defined in Annex A of fUML between Java and Activities.

Examples:

1. Usage of index starting from 0 instead of 1 in StateActivation::hasCompleted operation.
2. Constructor call with arguments in StateMachineEventAccepter::accept operation.
3. Usage of an iterative for loop instead a parallel for loop in StateActivation::enterRegion operation.

Any test in the PSSM test suite with a test driver that sends multiple signals to the model being tested may not currently be properly allowing all possible execution traces. This is because itt cannot, in general, be presumed that event occurrences are received in the order they are sent, even if they are all sent from the same thread. This was always true in fUML (per the statement of “the semantics of inter-object communications mechanisms” in subclause 2.4 of the spec), but it is completely, formally clear in fUML 1.3, in which EventOccurrence is an active class, such that all event occurrences are sent concurrently with each other.

For example, consider test Transition 007 (described in subclause 9.3.3.2 of the PSSM beta spec). The tester behavior for this test sequentially sends three signal instances: AnotherSignal, Continue and Continue again. However, while these signals are sent sequentially, there is no guarantee they will be received by the tested state machine in the same order. For example, one of the Continue signal instances could be received before the AnotherSignal instance, which would cause the state machine (as shown in Fig. 9.12) to take transition T3 to S2 and never get to S3.

Rather than try to capture all the possible traces that should be allowed by the such tests a s currently modeled, it would be better to modify the tests so that they should only produce the trace that is currently suspected. This can be done by having the state machine under test send signals back to the tester, in order to coordinate the sending of sequential signals. For example, in the case of Transition 007, the state machine could send signals back to the tester as part of the doTraversial behaviors for transitions T1 and T2. The test behavior would then have to include accept event actions in order to wait between the send signal actions. (Of course, to allow the test to send signals back to the tester, either the Tester/Target association in the test architecture would need to be made bidirectional, or some signaling mechanism would need to be provided through the SemanticTest class.)

Section 9.2.2.2.3 states: "The classifier behavior of a semantic test has the TestCase stereotype applied."

The source of the TestCase stereotype is not mentioned. Presumably, it is UTP, but the relationship of PSSM and UTP is not further described except a list of definitions from the UTP specification including Test Case on page 61.

The test case stereotype requires a return parameter of type VerdictKind. That is not implemented by PSSM.

Regarding the general OMG requirement for OMG specifications to reuse other specifications if possible, I propose to integrate the test case stereotype including the verdict concept from UTP.

The text for the semantics of exiting the source of a local transition appears incomplete; the first paragraph provides a condition under which the source cannot be exited, but if that condition is not met, does not describe how the source should be exited.