This is xnu-4903.221.2. See this file in:
#ifdef T_NAMESPACE
#undef T_NAMESPACE
#endif
#define T_NAMESPACE "xnu.ipc"
#include <darwintest.h>
#include <mach/mach.h>
#include <stdlib.h>
#include <stdio.h>


T_DECL(mach_port_mod_refs, "mach_port_mod_refs"){
	mach_port_t port_set;
	mach_port_t port;
	int ret;

	ret = mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_PORT_SET, &port_set);
	T_ASSERT_MACH_SUCCESS(ret, "mach_port_allocate MACH_PORT_RIGHT_PORT_SET");

	ret = mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_RECEIVE, &port);
	T_ASSERT_MACH_SUCCESS(ret, "mach_port_allocate MACH_PORT_RIGHT_RECEIVE");


	/*
	 * Test all known variants of port rights on each type of port
	 */

	/* can't subtract a send right if it doesn't exist */
	ret = mach_port_mod_refs(mach_task_self(), port, MACH_PORT_RIGHT_SEND, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs SEND: -1 on a RECV right");

	/* can't subtract a send once right if it doesn't exist */
	ret = mach_port_mod_refs(mach_task_self(), port, MACH_PORT_RIGHT_SEND_ONCE, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs SEND_ONCE: -1 on a RECV right");

	/* can't subtract a PORT SET right if it's not a port set */
	ret = mach_port_mod_refs(mach_task_self(), port, MACH_PORT_RIGHT_PORT_SET, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs PORT_SET: -1 on a RECV right");

	/* can't subtract a dead name right if it doesn't exist */
	ret = mach_port_mod_refs(mach_task_self(), port, MACH_PORT_RIGHT_DEAD_NAME, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs DEAD_NAME: -1 on a RECV right");

	/* can't subtract a LABELH right if it doesn't exist */
	ret = mach_port_mod_refs(mach_task_self(), port, MACH_PORT_RIGHT_LABELH, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs LABELH: -1 on a RECV right");

	/* can't subtract an invalid right-type */
	ret = mach_port_mod_refs(mach_task_self(), port, MACH_PORT_RIGHT_NUMBER, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_VALUE, "mach_port_mod_refs NUMBER: -1 on a RECV right");

	/* can't subtract an invalid right-type */
	ret = mach_port_mod_refs(mach_task_self(), port, MACH_PORT_RIGHT_NUMBER + 1, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_VALUE, "mach_port_mod_refs NUMBER+1: -1 on a RECV right");


	/* can't subtract a send right if it doesn't exist */
	ret = mach_port_mod_refs(mach_task_self(), port_set, MACH_PORT_RIGHT_SEND, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs SEND: -1 on a PORT_SET right");

	/* can't subtract a send once right if it doesn't exist */
	ret = mach_port_mod_refs(mach_task_self(), port_set, MACH_PORT_RIGHT_SEND_ONCE, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs SEND_ONCE: -1 on a PORT_SET right");

	/* can't subtract a receive right if it's a port set */
	ret = mach_port_mod_refs(mach_task_self(), port_set, MACH_PORT_RIGHT_RECEIVE, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs RECV: -1 on a PORT_SET right");

	/* can't subtract a dead name right if it doesn't exist */
	ret = mach_port_mod_refs(mach_task_self(), port_set, MACH_PORT_RIGHT_DEAD_NAME, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs DEAD_NAME: -1 on a PORT_SET right");

	/* can't subtract a LABELH right if it doesn't exist */
	ret = mach_port_mod_refs(mach_task_self(), port_set, MACH_PORT_RIGHT_LABELH, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_RIGHT, "mach_port_mod_refs LABELH: -1 on a PORT_SET right");

	/* can't subtract an invalid right-type */
	ret = mach_port_mod_refs(mach_task_self(), port_set, MACH_PORT_RIGHT_NUMBER, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_VALUE, "mach_port_mod_refs NUMBER: -1 on a PORT_SET right");

	/* can't subtract an invalid right-type */
	ret = mach_port_mod_refs(mach_task_self(), port_set, MACH_PORT_RIGHT_NUMBER + 1, -1);
	T_ASSERT_EQ(ret, KERN_INVALID_VALUE, "mach_port_mod_refs NUMBER+1: -1 on a PORT_SET right");

	/*
	 * deallocate the ports/sets
	 */
	ret= mach_port_mod_refs(mach_task_self(), port_set, MACH_PORT_RIGHT_PORT_SET, -1);
	T_ASSERT_MACH_SUCCESS(ret, "mach_port_mod_refs(PORT_SET, -1)");

	ret= mach_port_mod_refs(mach_task_self(), port, MACH_PORT_RIGHT_RECEIVE, -1);
	T_ASSERT_MACH_SUCCESS(ret, "mach_port_mod_refs(RECV_RIGHT, -1)");
}