To build for test of SoftHSM with static linking:
make p11test

To build for testing another p11 module provided as shared library:
make p11test_DEPENDENCIES= p11test_LDADD= CPPFLAGS=-DP11M=\\\"./p11m.so\\\" p11test
Substitute ./p11m.so with the path to your shared library.
Note that nothing else of SoftHSMv2 has to be built in order to build the test of an external p11.

To run the test with first a test summary and then specific output of each failure:
./p11test

To get output of each test after it is executed:
./p11test direct

To run a specific test:
./p11test ObjectTests::testArrayAttribute
Substitute 'ObjectTests::testArrayAttribute' with the test you want to run.