diff --git a/test/test_emulation.c b/test/test_emulation.c
index 8ccc71d..d661ad1 100644
--- a/test/test_emulation.c
+++ b/test/test_emulation.c
@@ -766,6 +766,31 @@ ATF_TC_BODY(emul_sta, tc)
 	bus_finish(&b);
 }
 
+ATF_TC_WITHOUT_HEAD(emul_sty);
+ATF_TC_BODY(emul_sty, tc)
+{
+	rk65c02emu_t e;
+	bus_t b;
+
+	b = bus_init_with_default_devs();
+	e = rk65c02_init(&b);
+
+	/* STY zero page */
+	e.regs.Y = 0xAA;
+	ATF_REQUIRE(rom_start(&e, "test_emulation_sty_zp.rom", tc));
+	ATF_CHECK(bus_read_1(&b, 0x20) == 0xAA);
+	/* STY zero page X */
+	e.regs.Y = 0x55;
+	e.regs.X = 0x1;
+	ATF_REQUIRE(rom_start(&e, "test_emulation_sty_zpx.rom", tc));
+	ATF_CHECK(bus_read_1(&b, 0x20) == 0x55);
+	/* STY absolute */
+	e.regs.Y = 0xAA;
+	ATF_REQUIRE(rom_start(&e, "test_emulation_sty_abs.rom", tc));
+	ATF_CHECK(bus_read_1(&b, 0x2010) == 0xAA);
+
+}
+
 ATF_TC_WITHOUT_HEAD(emul_ora);
 ATF_TC_BODY(emul_ora, tc)
 {
@@ -1747,6 +1772,7 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, emul_stack);
 	ATF_TP_ADD_TC(tp, emul_txa_tya_tax_tay);
 	ATF_TP_ADD_TC(tp, emul_sta);
+	ATF_TP_ADD_TC(tp, emul_sty);
 	ATF_TP_ADD_TC(tp, emul_sbc);
 	ATF_TP_ADD_TC(tp, emul_sbc_16bit);
 	ATF_TP_ADD_TC(tp, emul_sbc_bcd);
diff --git a/test/test_emulation_sty_abs.s b/test/test_emulation_sty_abs.s
new file mode 100644
index 0000000..cf7cebd
--- /dev/null
+++ b/test/test_emulation_sty_abs.s
@@ -0,0 +1,3 @@
+start:  sty 0x2010
+	stp
+
diff --git a/test/test_emulation_sty_zp.s b/test/test_emulation_sty_zp.s
new file mode 100644
index 0000000..842a753
--- /dev/null
+++ b/test/test_emulation_sty_zp.s
@@ -0,0 +1,3 @@
+start:  sty 0x20
+	stp
+
diff --git a/test/test_emulation_sty_zpx.s b/test/test_emulation_sty_zpx.s
new file mode 100644
index 0000000..c9b5a8c
--- /dev/null
+++ b/test/test_emulation_sty_zpx.s
@@ -0,0 +1,3 @@
+start:  sty 0x1F,X
+	stp
+