t: add null fairshare test

Add a new test to t1001-mf-priority-basic.t that sends a
fake payload with an empty fairshare key-value pair to
ensure that if a job is submitted that relies on that fairshare
value, an exception will be raised on that job and a priority
of 0 will be set.

t/t1001-mf-priority-basic.t

@@ -123,4 +123,31 @@ test_expect_success 'reject job when invalid bank format is passed in' '
 	grep "unable to unpack bank arg" invalid_fmt.out
 '
 
+test_expect_success 'create a fake payload with an empty fairshare key-value pair' '
+	cat <<-EOF >empty_fairshare.py
+	import flux
+	import pwd
+	import getpass
+
+	username = getpass.getuser()
+	userid = pwd.getpwnam(username).pw_uid
+	# create a JSON payload
+	data = {"userid": str(userid), "bank": "account4", "default_bank": "account3", "fairshare": "", "max_jobs": "10"}
+	flux.Flux().rpc("job-manager.mf_priority.rec_update", data).get()
+	EOF
+'
+
+test_expect_success 'update plugin with sample test data' '
+	flux python empty_fairshare.py
+'
+
+test_expect_success 'submit a job with new bank and empty fairshare results in a held job' '
+	jobid=$(flux mini submit --setattr=system.bank=account4 -n1 hostname) &&
+	flux job wait-event -f json $jobid priority | jq '.context.priority' > job7.test &&
+	cat <<-EOF >job7.expected &&
+	0
+	EOF
+	test_cmp job7.expected job7.test
+'
+
 test_done