cas_test.db

record(ao, "test:ao") {
    field(ASG, "rps_threshold")
    field(DRVH, "10")
    field(DRVL, "0")
}

record(bo, "test:bo") {
    field(ASG, "rps_lock")
    field(ZNAM, "OUT")
    field(ONAM, "IN")
}

record(ao, "test:ao2") {
    field(DRVH, "5")
    field(DRVL, "1")
}

record(bo, "test:permit") {
    field(VAL, "0")
    field(PINI, "1") # get rid of INVALID status
    field(ZNAM, "DISABLED")
    field(ONAM, "ENABLED")
}

crit_sig_rules.cfg

ASG(DEFAULT) {
    RULE(1,READ)
    RULE(1,WRITE,TRAPWRITE)
}

ASG(rps_threshold) {
    INPA("$(P):permit")
    RULE(1, READ)
    RULE(0, WRITE, TRAPWRITE) {
        CALC("A=1")
    }
    RULE(1, WRITE, TRAPWRITE) {
        CALC("A=0")
    }
}

ASG(rps_lock) {
    INPA("$(P):permit")
    RULE(1, READ)
    RULE(1, WRITE, TRAPWRITE) {
        CALC("A=0")
    }
}

test_cas.py

#!/usr/bin/env python

import subprocess
import epics


def softioc():
    proc = subprocess.Popen(['softIoc', '-m', 'P=test', '-a', "crit_sig_rules.cfg",
                             '-d', "cas_test.db"],
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE)
    return proc

def pvs():
    pvlist = ['test:ao', 'test:ao.DRVH', 'test:bo', 'test:ao2',
              'test:permit']
    pvs = dict()
    for name in pvlist:
        pv = epics.PV(name)
        pv.wait_for_connection()
        pvs[pv.pvname] = pv

    return pvs

if __name__ == '__main__':
    proc = softioc()
    pvs = pvs()
    
    for pv in pvs.values():
        assert pv.connected
       
    # with the Permit DISABLED, access should be r/w
    assert pvs['test:permit'].get(as_string=True) == 'DISABLED'

    # with the permit disabled, all test pvs should be readable/writable
    for pv in pvs.values():
        assert pv.read_access and pv.write_access
 
    # Activate the Permit. CAS rules are now active.
    pvs['test:permit'].put(1, wait=True)
    assert pvs['test:permit'].get(as_string=True) == 'ENABLED'
    
    assert pvs['test:bo'].read_access is True
    # XXX THIS FAILS AND IT SHOULD NOT XXX
    assert pvs['test:bo'].write_access is False
    # this would also fail
    assert pvs['test:ao.DRVH'].write_access is False