diff --git a/test/Kyuafile b/test/Kyuafile
index cb6d634..2df6928 100644
--- a/test/Kyuafile
+++ b/test/Kyuafile
@@ -6,4 +6,5 @@ atf_test_program{name='test_bus'}
 atf_test_program{name='test_emulation'}
 atf_test_program{name='test_assemble'}
 atf_test_program{name='test_stepping'}
+atf_test_program{name='test_interrupt'}
 
diff --git a/test/Makefile b/test/Makefile
index fbd6a87..f9066cd 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -22,8 +22,8 @@ test_emulation : test_emulation.o $(UTILS) $(RK6502LIB)
 test_assemble : test_assemble.o $(UTILS) $(RK6502LIB)
 	$(CC) -o $@ $(LDFLAGS) $< $(UTILS) $(RK6502LIB)
 
-#test_interrupt: test_interrupt.o $(UTILS) $(RK6502LIB)
-#	$(CC) -o $@ $(LDFLAGS) $< $(UTILS) $(RK6502LIB)
+test_interrupt: test_interrupt.o $(UTILS) $(RK6502LIB)
+	$(CC) -o $@ $(LDFLAGS) $< $(UTILS) $(RK6502LIB)
 
 %.rom : %.s
 	$(VASM) $(VASMFLAGS) -o $@ $< 
diff --git a/test/test_interrupt.c b/test/test_interrupt.c
new file mode 100644
index 0000000..2634bd0
--- /dev/null
+++ b/test/test_interrupt.c
@@ -0,0 +1,70 @@
+#include <atf-c.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include "bus.h"
+#include "rk65c02.h"
+#include "instruction.h"
+#include "utils.h"
+
+/*
+ * Test case for software generated interrupt (by BRK instruction).
+ */
+ATF_TC_WITHOUT_HEAD(intr_brk);
+ATF_TC_BODY(intr_brk, tc)
+{
+	const uint16_t isr_addr = 0xC100;
+
+	rk65c02emu_t e;	
+	bus_t b;
+
+
+	b = bus_init();
+	e = rk65c02_init(&b);
+
+	e.regs.PC = ROM_LOAD_ADDR;
+	e.regs.SP = 0xFF;
+
+	bus_write_1(&b, 0x10, 0x40);
+
+	ATF_REQUIRE(bus_load_file(&b, ROM_LOAD_ADDR,
+	    rom_path("test_interrupt_brk.rom", tc)));
+
+	ATF_REQUIRE(bus_load_file(&b, isr_addr,
+	    rom_path("test_interrupt_brk_isr.rom", tc)));
+
+        bus_write_1(&b, VECTOR_IRQ, isr_addr & 0xFF);
+        bus_write_1(&b, VECTOR_IRQ+1, isr_addr >> 8);
+
+	/* Execute first instruction, of the main program, which is a nop... */
+	rk65c02_step(&e, 1);
+	rk65c02_dump_regs(&e);
+	/* BRK is next, save its address... */
+	//brkaddr = e.regs.PC + 1;
+	/* Execute BRK instruction, which should start ISR (regardless of IRQ disable flag). */
+	rk65c02_step(&e, 1);
+	rk65c02_dump_regs(&e);
+	rk65c02_dump_stack(&e, 0x4);
+	/* Are we in ISR really? */
+	ATF_CHECK(e.regs.PC == isr_addr);
+	ATF_CHECK(e.regs.P & P_IRQ_DISABLE);
+
+	/* XXX: separate test case is needed to check return to main program. */
+
+	/*
+	rk65c02_step(&e, 1);
+	rk65c02_dump_regs(&e);
+	rk65c02_start(&e);
+	*/
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, intr_brk);
+
+	return (atf_no_error());
+}
+
diff --git a/test/test_interrupt_brk.s b/test/test_interrupt_brk.s
new file mode 100644
index 0000000..d373ea4
--- /dev/null
+++ b/test/test_interrupt_brk.s
@@ -0,0 +1,5 @@
+start:	nop
+	brk
+	nop
+	stp
+
diff --git a/test/test_interrupt_brk_isr.s b/test/test_interrupt_brk_isr.s
new file mode 100644
index 0000000..7450827
--- /dev/null
+++ b/test/test_interrupt_brk_isr.s
@@ -0,0 +1,4 @@
+isr:	lda #0xAA
+	ldx #0x55
+	ldy #0xFF
+