diff --git a/emulator/src/components.c b/emulator/src/components.c
index 5a90d37..788746a 100644
--- a/emulator/src/components.c
+++ b/emulator/src/components.c
@@ -34,7 +34,7 @@ static word_t rotl(word_t a, word_t n) { return (a << n) | (a >> (sizeof(word_t)
  */
 word_t alu(ALUOperation op, word_t a, word_t b, uint8_t *flags) {
 
-    word_t result;
+    word_t result = 0;
     *flags = 0;
 
     switch (op) {
@@ -61,7 +61,10 @@ word_t alu(ALUOperation op, word_t a, word_t b, uint8_t *flags) {
         result = a * b;
         break;
     case ALU_DIV:
-        result = a / b;
+        if (b == 0)
+            result = 0;
+        else
+            result = a / b;
         break;
     case ALU_LSL:
         result = a << b;
@@ -76,12 +79,11 @@ word_t alu(ALUOperation op, word_t a, word_t b, uint8_t *flags) {
         result = rotr(a, b);
         break;
     case ALU_NOOP:
-        result = 0;
         break;
     }
 
     // TODO implement flags for all operations
-    if (result == 0) *flags |= (0xFF & FLAG_ZERO);
+    if (result == 0 && op != ALU_NOOP) *flags |= (0xFF & FLAG_ZERO);
     if (result & 0x8000) *flags |= (0xFF & FLAG_NEGATIVE);
 
     return result;
diff --git a/emulator/tests/main.c b/emulator/tests/main.c
index 09744ad..5f8932e 100644
--- a/emulator/tests/main.c
+++ b/emulator/tests/main.c
@@ -1,8 +1,10 @@
 #include "../src/components.h"
 #include <assert.h>
+#include <stdint.h>
 #include <stdio.h>
 
 static void test_alu_add(void) {
+    // TODO revisit when carry and overflow are added
     uint8_t flags;
 
     assert(alu(ALU_ADD, 1, 3, &flags) == 4);
@@ -16,6 +18,20 @@ static void test_alu_add(void) {
     assert(flags & FLAG_NEGATIVE);
 }
 
+static void test_alu_sub(void) {
+    // TODO revisit when carry and overflow are added
+    uint8_t flags;
+
+    assert(alu(ALU_SUB, 5, 1, &flags) == 4);
+    assert(flags == 0);
+
+    assert(alu(ALU_SUB, 1, 1, &flags) == 0);
+    assert(flags & FLAG_ZERO);
+
+    assert(alu(ALU_SUB, 1, 2, &flags) == 0xFFFF);
+    assert(flags & FLAG_NEGATIVE);
+}
+
 static void test_alu_and(void) {
     uint8_t flags;
 
@@ -69,6 +85,7 @@ static void test_alu_rb(void) {
 }
 
 static void test_alu_mul(void) {
+    // TODO revisit when carry and overflow are added
     uint8_t flags;
 
     assert(alu(ALU_MUL, 5, 5, &flags) == 25);
@@ -84,6 +101,23 @@ static void test_alu_mul(void) {
     assert(flags == 0);
 }
 
+static void test_alu_div(void) {
+    // TODO revisit when carry and overflow are added
+    uint8_t flags;
+
+    assert(alu(ALU_DIV, 5, 5, &flags) == 1);
+    assert(flags == 0);
+
+    assert(alu(ALU_DIV, 0, 10, &flags) == 0);
+    assert(flags & FLAG_ZERO);
+
+    assert(alu(ALU_DIV, 1, 0, &flags) == 0);
+    assert(flags & FLAG_ZERO);
+
+    assert(alu(ALU_DIV, 0xFFFF, 13107, &flags) == 5);
+    assert(flags == 0);
+}
+
 static void test_alu_lsl(void) {
     uint8_t flags;
 
@@ -97,18 +131,79 @@ static void test_alu_lsl(void) {
     assert(flags & FLAG_NEGATIVE);
 }
 
+static void test_alu_lsr(void) {
+    uint8_t flags;
+
+    assert(alu(ALU_LSR, 2, 1, &flags) == 1);
+    assert(flags == 0);
+
+    assert(alu(ALU_LSR, 0x1, 1, &flags) == 0);
+    assert(flags & FLAG_ZERO);
+
+    assert(alu(ALU_LSR, 0x8000, 2, &flags) == 0x2000);
+    assert(flags == 0);
+}
+
+static void test_alu_noop(void) {
+    uint8_t flags;
+
+    assert(alu(ALU_NOOP, 7, 3, &flags) == 0);
+    assert(flags == 0);
+
+    assert(alu(ALU_NOOP, 4, 0, &flags) == 0);
+    assert(flags == 0);
+
+    assert(alu(ALU_NOOP, 18, 10002, &flags) == 0);
+    assert(flags == 0);
+}
+
+static void test_alu_rol(void) {
+    uint8_t flags;
+
+    assert(alu(ALU_ROL, 0x8000, 2, &flags) == 0x0002);
+    assert(flags == 0);
+
+    assert(alu(ALU_ROL, 0x4000, 1, &flags) == 0x8000);
+    assert(flags & FLAG_NEGATIVE);
+
+    assert(alu(ALU_ROL, 0x4000, 2, &flags) == 0x0001);
+    assert(flags == 0);
+
+    assert(alu(ALU_ROL, 0x4010, 1, &flags) == 0x8020);
+    assert(flags & FLAG_NEGATIVE);
+}
+
+static void test_alu_ror(void) {
+    uint8_t flags;
+
+    assert(alu(ALU_ROR, 0x8000, 2, &flags) == 0x2000);
+    assert(flags == 0);
+
+    assert(alu(ALU_ROR, 0x0001, 1, &flags) == 0x8000);
+    assert(flags & FLAG_NEGATIVE);
+
+    assert(alu(ALU_ROR, 0x4010, 1, &flags) == 0x2008);
+    assert(flags == 0);
+}
+
 int main(void) {
 
     puts("Running tests...");
 
     /* ALU TESTS */
     test_alu_add();
+    test_alu_sub();
     test_alu_and();
     test_alu_or();
     test_alu_not();
     test_alu_rb();
     test_alu_mul();
+    test_alu_div();
     test_alu_lsl();
+    test_alu_lsr();
+    test_alu_rol();
+    test_alu_ror();
+    test_alu_noop();
 
     return 0;
 }