diff --git a/.gitignore b/.gitignore
index 9eca6c8..9be162f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
+*.sw*
 *.a
 *.o
diff --git a/src/do_cycle_word.c b/src/do_cycle_word.c
index 2599d13..d743e59 100644
--- a/src/do_cycle_word.c
+++ b/src/do_cycle_word.c
@@ -116,13 +116,13 @@ int msp430_do_cycle_dual_operand(msp430_t *state, uint16_t opcode)
 		// ADD
 		uint32_t res = *src + *dst;
 		uint16_t sr = 0;
-		if ((int16_t)res < 0)
+		if ((int16_t)(res & 0xFFFF) < 0)
 			sr |= MSP430_SR_N;
-		if (res == 0)
+		if ((res & 0xFFFF) == 0)
 			sr |= MSP430_SR_Z;
 		if ((res & 0xFFFF0000) != 0)
 			sr |= MSP430_SR_C;
-		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+		if (((*src & 0x8000) ^ (*dst & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
 			sr |= MSP430_SR_V;
 		*dst = (uint16_t)res;
 		state->reg[2] =	sr;
@@ -137,7 +137,7 @@ int msp430_do_cycle_dual_operand(msp430_t *state, uint16_t opcode)
 			sr |= MSP430_SR_Z;
 		if ((res & 0xFFFF0000) != 0)
 			sr |= MSP430_SR_C;
-		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+		if (((*src & 0x8000) ^ (*dst & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
 			sr |= MSP430_SR_V;
 		*dst = (uint16_t)res;
 		state->reg[2] =	sr;
@@ -152,7 +152,7 @@ int msp430_do_cycle_dual_operand(msp430_t *state, uint16_t opcode)
 			sr |= MSP430_SR_Z;
 		if ((res & 0xFFFF0000) != 0)
 			sr |= MSP430_SR_C;
-		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+		if (((*src & 0x8000) ^ (*dst & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
 			sr |= MSP430_SR_V;
 		*dst = (uint16_t)res;
 		state->reg[2] =	sr;
@@ -167,7 +167,7 @@ int msp430_do_cycle_dual_operand(msp430_t *state, uint16_t opcode)
 			sr |= MSP430_SR_Z;
 		if ((res & 0xFFFF0000) != 0) // TODO confirm
 			sr |= MSP430_SR_C;
-		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+		if (((*src & 0x8000) ^ (*dst & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
 			sr |= MSP430_SR_V;
 		*dst = (uint16_t)res;
 		state->reg[2] =	sr;
@@ -182,7 +182,7 @@ int msp430_do_cycle_dual_operand(msp430_t *state, uint16_t opcode)
 			sr |= MSP430_SR_Z;
 		if ((res & 0xFFFF0000) != 0)
 			sr |= MSP430_SR_C;
-		if (((*src & 0x8000) ^ (*src & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
+		if (((*src & 0x8000) ^ (*dst & 0x8000)) == 0 && (*src & 0x8000) != (res & 0x8000))
 			sr |= MSP430_SR_V;
 		state->reg[2] =	sr;
 		break; }
diff --git a/tests/Makefile b/tests/Makefile
index 43d4134..4d66f39 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -2,8 +2,13 @@ DEBUG := #-DDEBUG
 
 LIB430COREDIR = ..
 
-TEST_CSRC = test.c
-TEST_OUT = $(patsubst %.c,%.o,$(TEST_CSRC))
+TEST_CSRC = \
+	    mov_constants.s \
+	    mov_addressing_dest.s \
+	    mov_addressing_source.s \
+	    add.s
+
+TEST_OUT = $(patsubst %.c,%.o,$(patsubst %.s,%.o,$(TEST_CSRC)))
 
 all: $(LIB430COREDIR)/lib430core.a $(TEST_OUT)
 
@@ -12,13 +17,26 @@ $(LIB430COREDIR)/lib430core.a:
 
 .c.o:
 	@echo "Testing" $< "..."
-	@msp430-elf32-gcc -T../link.ld $< -o tmp.elf -nostdlib -lgcc -lc
+	@msp430-elf32-gcc -T../link.ld -O0 -ggdb -g3 $< -o tmp.elf -nostdlib -lgcc -lc
+	@msp430-elf32-objcopy -Obinary tmp.elf tmp.bin
+	@echo "#define TESTBIN \\" > test.h
+	@od -t x1 tmp.bin | awk '{for (i=2; i<=NF; i++) printf "0x" $$i ", "}' >> test.h
+	@printf "\n#define TESTSIZE %u \n" $$(msp430-elf32-objdump tmp.elf -Dj .text | grep -E "^\s+[0-9a-fA-F]+:" | wc -l) >> test.h
+	@echo >> test.h
+	@gcc -Os -ggdb -g3 -Wall -W -pedantic $(DEBUG) -I../src -o tmp \
+		test_$< -L$(LIB430COREDIR) -l430core
+	@./tmp
+	@rm tmp.elf tmp.bin tmp test.h
+
+.s.o:
+	@echo "Testing" $< "..."
+	@msp430-elf32-gcc -T../link.ld -O0 $< -o tmp.elf -nostdlib -lgcc -lc
 	@msp430-elf32-objcopy -Obinary tmp.elf tmp.bin
 	@echo "#define TESTBIN \\" > test.h
 	@od -t x1 tmp.bin | awk '{for (i=2; i<=NF; i++) printf "0x" $$i ", "}' >> test.h
 	@printf "\n#define TESTSIZE %u \n" $$(msp430-elf32-objdump tmp.elf -Dj .text | grep -E "^\s+[0-9a-fA-F]+:" | wc -l) >> test.h
 	@echo >> test.h
 	@gcc -Os -ggdb -g3 -Wall -W -pedantic $(DEBUG) -I../src -o tmp \
-		core_test.c -L$(LIB430COREDIR) -l430core
-	@./tmp > log
-	@rm log tmp.elf tmp.bin tmp test.h
+		test_$(patsubst %.s,%.c,$<) -L$(LIB430COREDIR) -l430core
+	@./tmp
+	@rm tmp.elf tmp.bin tmp test.h
diff --git a/tests/add.s b/tests/add.s
new file mode 100644
index 0000000..d811316
--- /dev/null
+++ b/tests/add.s
@@ -0,0 +1,16 @@
+main:
+	mov #13, r5
+	add #15, r5
+	mov r2, r12
+	mov #-7, r6
+	add #7, r6
+	mov r2, r13
+	mov #0xfffa, r7
+	add #0x001e, r7
+	mov r2, r14
+	mov #-32700, r8
+	add #-800, r8
+	mov r2, r15
+	mov #2, r9
+	add #-5, r9
+	ret
diff --git a/tests/mov_addressing_dest.s b/tests/mov_addressing_dest.s
new file mode 100644
index 0000000..8698a92
--- /dev/null
+++ b/tests/mov_addressing_dest.s
@@ -0,0 +1,11 @@
+main:
+	mov #64, r4
+	mov r4, r5
+	mov #42, r4
+	mov r4, @r5
+	mov r4, 4(r5)
+	mov #50, mem
+	mov &mem, &0x50
+	ret
+
+mem: .byte 5
diff --git a/tests/mov_addressing_source.s b/tests/mov_addressing_source.s
new file mode 100644
index 0000000..21f0cb3
--- /dev/null
+++ b/tests/mov_addressing_source.s
@@ -0,0 +1,14 @@
+main:
+	mov #42, &0x40
+	mov #44, &0x42
+	mov #46, &0x44
+	mov #0x40, r4
+	mov r4, r5
+	mov 4(r5), r6
+	mov @r5+, r7
+	mov @r5, r8
+	mov var, r9
+	mov &0x44, r10
+	ret
+
+var: .byte 13
diff --git a/tests/mov_constants.s b/tests/mov_constants.s
new file mode 100644
index 0000000..d77eb51
--- /dev/null
+++ b/tests/mov_constants.s
@@ -0,0 +1,8 @@
+main:
+	mov #0, r4
+	mov #1, r5
+	mov #2, r6
+	mov #-1, r7
+	mov #4, r8
+	mov #8, r9
+	ret
diff --git a/tests/test.c b/tests/test.c
deleted file mode 100644
index 8eb344a..0000000
--- a/tests/test.c
+++ /dev/null
@@ -1,8 +0,0 @@
-int main()
-{
-	volatile int *mem = (int *)0x200;
-	*mem = 24;
-	for (int i = 0; i < 8; ++i)
-		*mem += 2;
-	return *mem;
-}
diff --git a/tests/test_add.c b/tests/test_add.c
new file mode 100644
index 0000000..2f6bc00
--- /dev/null
+++ b/tests/test_add.c
@@ -0,0 +1,53 @@
+#include "core.h"
+#include "test.h"
+
+#include <stdio.h>
+
+static uint8_t mem[0x10000] = {
+	TESTBIN
+};
+
+static void dump_state(msp430_t *state)
+{
+	puts("MSP430 dump state:");
+	printf("R0/PC: 0x%04x R1/SP: 0x%04x R2/SR: 0x%04x R3:  0x%04x\n",
+		state->reg[0], state->reg[1], state->reg[2], state->reg[3]);
+	printf("R4:    0x%04x R5:    0x%04x R6:    0x%04x R7:  0x%04x\n",
+		state->reg[4], state->reg[5], state->reg[6], state->reg[7]);
+	printf("R8:    0x%04x R9:    0x%04x R10:   0x%04x R11: 0x%04x\n",
+		state->reg[8], state->reg[9], state->reg[10], state->reg[11]);
+	printf("R12:   0x%04x R13:   0x%04x R14:   0x%04x R15: 0x%04x\n\n",
+		state->reg[12], state->reg[13], state->reg[14], state->reg[15]);
+}
+
+int main()
+{
+	msp430_t state;
+	msp430_init_state(&state, mem);
+
+	int r;
+	do {
+		r = msp430_do_cycle(&state);
+		if (r < 0) {
+			printf("Failed to execute near PC=0x%04x!\n", state.reg[0]);
+			return 1;
+		}
+	} while (r != 1);
+
+	if (state.reg[5] != 28 ||
+	    state.reg[6] != 0 ||
+	    state.reg[7] != 0x18 ||
+	    state.reg[8] != 0x7d24 ||
+	    state.reg[9] != 0xfffd ||
+	    state.reg[12] != 0 ||
+	    state.reg[13] != 0x03 ||
+	    state.reg[14] != 0x01 ||
+	    state.reg[15] != 0x101)
+	{
+		dump_state(&state);
+		return 1;
+	}
+
+	return 0;
+}
+
diff --git a/tests/test_mov_addressing_dest.c b/tests/test_mov_addressing_dest.c
new file mode 100644
index 0000000..5db3df7
--- /dev/null
+++ b/tests/test_mov_addressing_dest.c
@@ -0,0 +1,50 @@
+#include "core.h"
+#include "test.h"
+
+#include <stdio.h>
+
+static uint8_t mem[0x10000] = {
+	TESTBIN
+};
+/*
+static void dump_state(msp430_t *state)
+{
+	puts("MSP430 dump state:");
+	printf("R0/PC: 0x%04x R1/SP: 0x%04x R2/SR: 0x%04x R3:  0x%04x\n",
+		state->reg[0], state->reg[1], state->reg[2], state->reg[3]);
+	printf("R4:    0x%04x R5:    0x%04x R6:    0x%04x R7:  0x%04x\n",
+		state->reg[4], state->reg[5], state->reg[6], state->reg[7]);
+	printf("R8:    0x%04x R9:    0x%04x R10:   0x%04x R11: 0x%04x\n",
+		state->reg[8], state->reg[9], state->reg[10], state->reg[11]);
+	printf("R12:   0x%04x R13:   0x%04x R14:   0x%04x R15: 0x%04x\n\n",
+		state->reg[12], state->reg[13], state->reg[14], state->reg[15]);
+}
+*/
+int main()
+{
+	msp430_t state;
+	msp430_init_state(&state, mem);
+
+	int r;
+	do {
+		r = msp430_do_cycle(&state);
+		if (r < 0) {
+			printf("Failed to execute near PC=0x%04x!\n", state.reg[0]);
+			return 1;
+		}
+	} while (r != 1);
+
+	if (state.reg[4] != 42 ||
+	    state.reg[5] != 64 ||
+	    *((uint16_t *)(state.mem + 64)) != 42 ||
+	    *((uint16_t *)(state.mem + 68)) != 42 ||
+	    *((uint16_t *)(state.mem + 0x50)) != 50)
+	{
+		return 1;
+	}
+
+	//dump_state(&state);
+
+	return 0;
+}
+
diff --git a/tests/core_test.c b/tests/test_mov_addressing_source.c
similarity index 82%
rename from tests/core_test.c
rename to tests/test_mov_addressing_source.c
index 08e2650..c35421e 100644
--- a/tests/core_test.c
+++ b/tests/test_mov_addressing_source.c
@@ -3,9 +3,10 @@
 
 #include <stdio.h>
 
-//#define DEBUG
+static uint8_t mem[0x10000] = {
+	TESTBIN
+};
 
-#ifdef DEBUG
 static void dump_state(msp430_t *state)
 {
 	puts("MSP430 dump state:");
@@ -18,34 +19,33 @@ static void dump_state(msp430_t *state)
 	printf("R12:   0x%04x R13:   0x%04x R14:   0x%04x R15: 0x%04x\n\n",
 		state->reg[12], state->reg[13], state->reg[14], state->reg[15]);
 }
-#endif // DEBUG
-
-static uint8_t mem[0x10000] = {
-	TESTBIN
-};
 
 int main()
 {
 	msp430_t state;
-
 	msp430_init_state(&state, mem);
 
-#ifdef DEBUG
-	dump_state(&state);
-#endif // DEBUG
 	int r;
 	do {
 		r = msp430_do_cycle(&state);
 		if (r < 0) {
 			printf("Failed to execute near PC=0x%04x!\n", state.reg[0]);
 			return 1;
-			//break;
 		}
+	} while (r != 1);
 
-#ifdef DEBUG
+	if (state.reg[4] != 0x40 ||
+	    state.reg[5] != 0x42 ||
+	    state.reg[6] != 46 ||
+	    state.reg[7] != 42 ||
+	    state.reg[8] != 44 ||
+	    state.reg[9] != 13 ||
+	    state.reg[10] != 46)
+	{
 		dump_state(&state);
-#endif // DEBUG
-	} while (r != 1);
+		return 1;
+	}
+
 
 	return 0;
 }
diff --git a/tests/test_mov_constants.c b/tests/test_mov_constants.c
new file mode 100644
index 0000000..f52b5ee
--- /dev/null
+++ b/tests/test_mov_constants.c
@@ -0,0 +1,36 @@
+#include "core.h"
+#include "test.h"
+
+#include <stdio.h>
+
+static uint8_t mem[0x10000] = {
+	TESTBIN
+};
+
+int main()
+{
+	msp430_t state;
+	msp430_init_state(&state, mem);
+
+	int r;
+	do {
+		r = msp430_do_cycle(&state);
+		if (r < 0) {
+			printf("Failed to execute near PC=0x%04x!\n", state.reg[0]);
+			return 1;
+		}
+	} while (r != 1);
+
+	if (state.reg[4] != 0 ||
+	    state.reg[5] != 1 ||
+	    state.reg[6] != 2 ||
+	    state.reg[7] != 0xFFFF ||
+	    state.reg[8] != 4 ||
+	    state.reg[9] != 8)
+	{
+		return 1;
+	}
+
+	return 0;
+}
+