diff --git a/src/main/java/org/fungover/haze/Command.java b/src/main/java/org/fungover/haze/Command.java
index 8fffbe13..767081af 100644
--- a/src/main/java/org/fungover/haze/Command.java
+++ b/src/main/java/org/fungover/haze/Command.java
@@ -1,6 +1,9 @@
 package org.fungover.haze;
 
 public enum Command {
-    SET, GET, DEL, PING, SETNX, EXISTS, SAVE, RPUSH, LPUSH, LPOP, RPOP, LLEN, LMOVE, LTRIM, AUTH, LINDEX, INCR, DECR
+
+    SET, GET, DEL, PING, SETNX, EXISTS, SAVE, RPUSH, LPUSH, LPOP, RPOP, LLEN, LMOVE, LTRIM, AUTH, LINDEX, INCR, DECR,LSET
+
+
 
 }
diff --git a/src/main/java/org/fungover/haze/HazeList.java b/src/main/java/org/fungover/haze/HazeList.java
index 41ded3ac..7f82c3d5 100644
--- a/src/main/java/org/fungover/haze/HazeList.java
+++ b/src/main/java/org/fungover/haze/HazeList.java
@@ -1,6 +1,7 @@
 package org.fungover.haze;
 import java.util.*;
 import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 import java.util.stream.Stream;
 
 public class HazeList {
@@ -297,4 +298,39 @@ private static String getKey(List<String> inputList) {
             key = inputList.get(1);
         return key;
     }
+
+        public String lSet(List<String> inputlist){
+        if (inputlist.size() < 4){
+            return "-Err Wrong number of arguments for LSET\r\n";
+        }
+        String key = getKey(inputlist);
+
+        if (!hazeDatabase.containsKey(key)){
+            return "-Err Key does not exist\r\n";
+        }
+            int index;
+            if (inputlist.get(2).equals("-1")) {
+
+                List<String> list = getValueAsList(hazeDatabase.getValue(key));
+                index = list.size() - 1;
+            } else {
+                try {
+                    index = Integer.parseInt(inputlist.get(2));
+                } catch (NumberFormatException e) {
+                    return "-Err invalid index\r\n";
+                }
+            }
+        String element = inputlist.get(3);
+        List<String> list = getValueAsList(hazeDatabase.getValue(key));
+
+        if (index < 0 || index >= list.size()){
+            return "-Err index out of bounds\r\n";
+        }
+        List <String> updatedList = IntStream.range(0, list.size()).
+                mapToObj(i -> i == index ? element : list.get(i)).toList();
+
+        hazeDatabase.addValue(key,listValueAsString(updatedList));
+        return "+OK\r\n";
+
+        }
 }
diff --git a/src/main/java/org/fungover/haze/Main.java b/src/main/java/org/fungover/haze/Main.java
index f8314b54..e95a9930 100644
--- a/src/main/java/org/fungover/haze/Main.java
+++ b/src/main/java/org/fungover/haze/Main.java
@@ -121,6 +121,7 @@ public static String executeCommand(HazeDatabase hazeDatabase, List<String> inpu
             case LMOVE -> hazeList.lMove(inputList);
             case LTRIM -> hazeList.callLtrim(inputList);
             case LINDEX -> hazeList.lIndex(inputList);
+            case LSET -> hazeList.lSet(inputList);
             case AUTH -> "+OK\r\n";
             case INCR -> hazeDatabase.increaseValue(inputList);
             case DECR -> hazeDatabase.decreaseValue(inputList);
diff --git a/src/test/java/org/fungover/haze/HazeListTest.java b/src/test/java/org/fungover/haze/HazeListTest.java
index 99f958fd..40c817fe 100644
--- a/src/test/java/org/fungover/haze/HazeListTest.java
+++ b/src/test/java/org/fungover/haze/HazeListTest.java
@@ -1,9 +1,9 @@
 package org.fungover.haze;
 import org.junit.jupiter.api.Test;
 import java.util.List;
-
-import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
+
 
 class HazeListTest {
 
@@ -15,21 +15,21 @@ class HazeListTest {
     void rPushWithTwoValuesShouldReturnTwo() {
         hazeList.rPush(List.of("", "key1", "value1"));
         String actual = hazeList.rPush(List.of("", "key1", "value2"));
-        assertEquals(":2\r\n",actual);
+        assertEquals(":2\r\n", actual);
     }
 
     @Test
     void lPushWithTwoValuesShouldReturnTwo() {
         hazeList.lPush(List.of("", "key1", "value1"));
         String actual = hazeList.lPush(List.of("", "key1", "value2"));
-        assertEquals(":2\r\n",actual);
+        assertEquals(":2\r\n", actual);
     }
 
     @Test
     void assertThatLPushWithMultipleValuesAddsInReverseOrder() {
         hazeList.lPush(List.of("", "key1", "value1", "value2"));
         String actual = hazeDatabase.getValue("key1");
-        assertEquals("value2\r\nvalue1",actual);
+        assertEquals("value2\r\nvalue1", actual);
     }
 
     @Test
@@ -37,14 +37,14 @@ void assertThatLPushMultipleTimesAddsInReverseOrder() {
         hazeList.lPush(List.of("", "key1", "value1"));
         hazeList.lPush(List.of("", "key1", "value2"));
         String actual = hazeDatabase.getValue("key1");
-        assertEquals("value2\r\nvalue1",actual);
+        assertEquals("value2\r\nvalue1", actual);
     }
 
     @Test
     void assertThatRPushWithMultipleValuesAddsInCorrectOrder() {
         hazeList.rPush(List.of("", "key1", "value1", "value2"));
         String actual = hazeDatabase.getValue("key1");
-        assertEquals("value1\r\nvalue2",actual);
+        assertEquals("value1\r\nvalue2", actual);
     }
 
     @Test
@@ -52,12 +52,12 @@ void assertThatRPushMultipleTimesAddsInCorrectOrder() {
         hazeList.rPush(List.of("", "key1", "value1"));
         hazeList.rPush(List.of("", "key1", "value2"));
         String actual = hazeDatabase.getValue("key1");
-        assertEquals("value1\r\nvalue2",actual);
+        assertEquals("value1\r\nvalue2", actual);
     }
 
     @Test
     void lPopShouldReturnNilStringWhenNoKeyIsPresent() {
-        String nilTest= hazeList.lPop("keyThatDontExist");
+        String nilTest = hazeList.lPop("keyThatDontExist");
         assertEquals("$5\r\n(nil)\r\n", nilTest);
     }
 
@@ -69,15 +69,15 @@ void lPopShouldReturnCorrectValues() {
     }
 
     @Test
-    void lPopShouldReturnBulkStringWithSix(){
+    void lPopShouldReturnBulkStringWithSix() {
         hazeList.rPush(List.of("", "key1", "value1", "value2"));
         String bulkStringSixChars = "$6\r\nvalue1\r\n";
         assertEquals(bulkStringSixChars, hazeList.lPop("key1"));
     }
 
     @Test
-    void lPopWithoutKeyShouldReturnCorrectErrorText(){
-        assertEquals("$5\r\n(nil)\r\n", hazeList.lPop("key1",1));
+    void lPopWithoutKeyShouldReturnCorrectErrorText() {
+        assertEquals("$5\r\n(nil)\r\n", hazeList.lPop("key1", 1));
     }
 
     @Test
@@ -100,7 +100,7 @@ void rPopShouldReturnValue2RespString() {
         hazeList.rPush(List.of("", "key1", "value1", "value2"));
 
         String expected = "$6\r\nvalue2\r\n";
-        assertEquals(expected, hazeList.rPop("key1" ));
+        assertEquals(expected, hazeList.rPop("key1"));
     }
 
     @Test
@@ -112,7 +112,7 @@ void rPopShouldReturnValuesInReverseOrder() {
     }
 
     @Test
-    void rPopWithCountShouldReturnNilBulkStringWhenKeyIsMissing(){
+    void rPopWithCountShouldReturnNilBulkStringWhenKeyIsMissing() {
         String nilFiveBulk = "$5\r\n(nil)\r\n";
         assertEquals(nilFiveBulk, hazeList.rPop("noKey", 2));
     }
@@ -130,7 +130,7 @@ void alLenWithMissingKeyShouldReturRspZero() {
     }
 
     @Test
-    void lMoveShouldMoveVal1FromLeftToLeft(){
+    void lMoveShouldMoveVal1FromLeftToLeft() {
         hazeList.rPush(List.of("", "key1", "val1", "val2"));
         hazeList.rPush(List.of("", "key2", "val3", "val4"));
         hazeList.lMove(List.of("", "key1", "key2", "LEFT", "LEFT"));
@@ -147,7 +147,7 @@ void lMoveShouldMoveVal1FromLeftToLeft(){
     }
 
     @Test
-    void lMoveShouldMoveVal1FromLeftToRight(){
+    void lMoveShouldMoveVal1FromLeftToRight() {
         hazeList.rPush(List.of("", "key1", "val1", "val2"));
         hazeList.rPush(List.of("", "key2", "val3", "val4"));
         hazeList.lMove(List.of("", "key1", "key2", "LEFT", "RIGHT"));
@@ -163,7 +163,7 @@ void lMoveShouldMoveVal1FromLeftToRight(){
     }
 
     @Test
-    void lMoveShouldMoveValuesFromRightToLeft(){
+    void lMoveShouldMoveValuesFromRightToLeft() {
         hazeList.rPush(List.of("", "key1", "val1", "val2"));
         hazeList.rPush(List.of("", "key2", "val3", "val4"));
         hazeList.lMove(List.of("", "key1", "key2", "RIGHT", "LEFT"));
@@ -179,18 +179,18 @@ void lMoveShouldMoveValuesFromRightToLeft(){
     }
 
     @Test
-    void lMoveShouldReturnCorrectErrorMessageWhenKeyIsMissing(){
+    void lMoveShouldReturnCorrectErrorMessageWhenKeyIsMissing() {
         String errorText = "-One or both keys is missing.\r\n";
-        assertEquals(errorText,hazeList.lMove(List.of("", "key1", "key2", "LEFT", "RIGHT")));
+        assertEquals(errorText, hazeList.lMove(List.of("", "key1", "key2", "LEFT", "RIGHT")));
     }
 
     @Test
-    void lMoveShouldReturnCorrectErrorMessageWhenListIsEmpty(){
+    void lMoveShouldReturnCorrectErrorMessageWhenListIsEmpty() {
         hazeList.rPush(List.of("", "key1", "val1"));
         hazeList.rPush(List.of("", "key2", "val2"));
         hazeList.lMove(List.of("", "key1", "key2", "LEFT", "RIGHT"));
         String errorText = "-The source list is empty.\r\n";
-        assertEquals(errorText,hazeList.lMove(List.of("", "key1", "key2", "LEFT", "RIGHT")));
+        assertEquals(errorText, hazeList.lMove(List.of("", "key1", "key2", "LEFT", "RIGHT")));
     }
 
     @Test
@@ -214,7 +214,7 @@ void testLMoveInvalidFromAndTo() {
     @Test
     void correctValuesShouldStayAfterTrim() {
         hazeList.rPush(List.of("", "key1", "val1", "val2", "val3", "val4", "val5"));
-        hazeList.lTrim("key1", 1,2);
+        hazeList.lTrim("key1", 1, 2);
         String databaseCsv = hazeList.hazeDatabase.getValue("key1");
         List<String> list1 = HazeList.getValueAsList(databaseCsv);
 
@@ -222,20 +222,20 @@ void correctValuesShouldStayAfterTrim() {
     }
 
     @Test
-    void lTrimShouldReturnErrorCorrectErrorTextWhenInputsAreOutOfRange(){
+    void lTrimShouldReturnErrorCorrectErrorTextWhenInputsAreOutOfRange() {
         hazeList.rPush(List.of("", "key1", "val1", "val2", "val3", "val4", "val5"));
         String correctErrorText = "-The inputs are outside the range of the list.\r\n";
         assertEquals(correctErrorText, hazeList.lTrim("key1", 2, 7));
     }
 
     @Test
-    void lTrimShouldReturnCorrectErrorTextWhenKeyIsMissing(){
+    void lTrimShouldReturnCorrectErrorTextWhenKeyIsMissing() {
         String correctErrorText = "-The key is not present in the database.\r\n";
         assertEquals(correctErrorText, hazeList.lTrim("key1", 2, 7));
     }
 
     @Test
-    void callLPopWithEmptyCountArrayShouldCallLopWithoutCount(){
+    void callLPopWithEmptyCountArrayShouldCallLopWithoutCount() {
         hazeList.rPush(List.of("", "key1", "val1", "val2", "val3"));
         String result = hazeList.callLPop(List.of("", "key1"));
         String expected = "$4\r\nval1\r\n";
@@ -243,7 +243,7 @@ void callLPopWithEmptyCountArrayShouldCallLopWithoutCount(){
     }
 
     @Test
-    void callLPopWithPopulatedArrayShouldCallLPopWithCount(){
+    void callLPopWithPopulatedArrayShouldCallLPopWithCount() {
         hazeList.rPush(List.of("", "key1", "val1", "val2", "val3"));
         String result = hazeList.callLPop(List.of("", "key1", "2", "3"));
         String expected = "*2\r\n$4\r\nval1\r\n$4\r\nval2\r\n";
@@ -251,7 +251,7 @@ void callLPopWithPopulatedArrayShouldCallLPopWithCount(){
     }
 
     @Test
-    void callRPopWithEmptyCountArrayShouldCallRopWithoutCount(){
+    void callRPopWithEmptyCountArrayShouldCallRopWithoutCount() {
         hazeList.rPush(List.of("", "key1", "val1", "val2", "val3"));
         String result = hazeList.callRPop(List.of("", "key1"));
         String expected = "$4\r\nval3\r\n";
@@ -259,7 +259,7 @@ void callRPopWithEmptyCountArrayShouldCallRopWithoutCount(){
     }
 
     @Test
-    void callLRopWithPopulatedArrayShouldCallRPopWithCount(){
+    void callLRopWithPopulatedArrayShouldCallRPopWithCount() {
         hazeList.rPush(List.of("", "key1", "val1", "val2", "val3"));
         String result = hazeList.callRPop(List.of("", "key1", "2", "3"));
         String expected = "*2\r\n$4\r\nval3\r\n$4\r\nval2\r\n";
@@ -267,51 +267,89 @@ void callLRopWithPopulatedArrayShouldCallRPopWithCount(){
     }
 
     @Test
-    void CallLtrimShouldCallLtrimWhenGivenAKeyAndTwoNummersAsArgument(){
+    void CallLtrimShouldCallLtrimWhenGivenAKeyAndTwoNummersAsArgument() {
         hazeList.rPush(List.of("", "key1", "val1", "val2", "val3", "val4", "val5"));
-        String actual = hazeList.callLtrim(List.of("", "key1","2", "4"));
+        String actual = hazeList.callLtrim(List.of("", "key1", "2", "4"));
         assertEquals("+OK\r\n", actual);
     }
 
     @Test
-    void CallLReturnCorrectErrorMessageWhenIncorrectNumberOfArgumentsIsReceived () {
+    void CallLReturnCorrectErrorMessageWhenIncorrectNumberOfArgumentsIsReceived() {
         String expected = "-Wrong number of arguments for LTRIM\r\n";
         assertEquals(expected, hazeList.callLtrim(List.of("", "key1")));
     }
 
     @Test
-    void CallLReturnCorrectErrorMessageWhenNotGivenNumbersAsArguments () {
+    void CallLReturnCorrectErrorMessageWhenNotGivenNumbersAsArguments() {
         String expected = "-Value is not an integer or out of range\r\n";
         assertEquals(expected, hazeList.callLtrim(List.of("", "key1", "horse", "Gunnar!")));
     }
 
     @Test
-    void parserWithBadInputShouldReturnZero(){
+    void parserWithBadInputShouldReturnZero() {
         assertEquals(0, HazeList.parser("This is not a number"));
     }
 
+        @Test
+        void lSetShouldUpdateValue()
+    {
+       hazeList.rPush(List.of("", "key1", "val1", "val2", "val3", "val4", "val5"));
+       hazeList.lSet(List.of("", "key1", "0", "hej"));
+       String asString = hazeDatabase.getValue("key1");
+       assertThat(asString).isEqualTo("hej\r\nval2\r\nval3\r\nval4\r\nval5");
+    }
 
     @Test
-    void callingLindexWithValidPositiveIndexReturnValue(){
-        hazeList.rPush(List.of("", "key2", "val1", "val2", "val3"));
-        assertThat(hazeList.lIndex(List.of("", "key2", "2"))).isEqualTo("$4\r\nval3\r\n");
+    void lSetWithIndexOutOfBoundsShouldReturnErrorMessage() {
+        hazeList.rPush(List.of("", "key1", "val1", "val2", "val3", "val4", "val5"));
+        assertThat(hazeList.lSet(List.of("", "key1", "6", "hej"))).isEqualTo("-Err index out of bounds\r\n");
     }
 
     @Test
-    void callingLindexWithIndexOutOfBoundsReturnNil(){
-        hazeList.rPush(List.of("", "key2", "val1", "val2", "val3"));
-        assertThat(hazeList.lIndex(List.of("", "key2", "3"))).isEqualTo("$5\r\n(nil)\r\n");
+    void lSetWithNonExistingKey() {
+        hazeList.rPush(List.of("", "key1", "val1", "val2", "val3", "val4", "val5"));
+        assertThat(hazeList.lSet(List.of("", "key2", "3", "hej"))).isEqualTo("-Err Key does not exist\r\n");
+    }
+
+    @Test
+    void lSetIndexWithValidNegativeIndexReturnValue() {
+        hazeList.rPush(List.of("", "key1", "val1", "val2", "val3", "val4", "val5"));
+        hazeList.lSet(List.of("", "key1", "-1", "howdy"));
+        String asString = hazeDatabase.getValue("key1");
+        assertThat(asString).isEqualTo("val1\r\nval2\r\nval3\r\nval4\r\nhowdy");
     }
 
     @Test
-    void callingLindexWithValidNegativeIndexReturnValue(){
+    void lSetNoKey() {
+        hazeList.rPush(List.of("", "", "val1", "val2", "val3"));
+        hazeList.lSet(List.of("", "", "0", "val1"));
+        String asString = hazeDatabase.getValue("");
+
+        assertThat(asString).isEqualTo("val1\r\nval2\r\nval3");
+    }
+
+    @Test
+    void lSetWithWrongNumberOFArguments() {
+        hazeList.rPush(List.of("", "key1", "val1"));
+        assertThat(hazeList.lSet(List.of("", "key1", "hej"))).isEqualTo("-Err Wrong number of arguments for LSET\r\n");
+    }
+
+    @Test
+    void lSetWithWrongIndex() {
+        hazeList.rPush(List.of("", "key1", "val1", "val2", "val3", "val4", "val5"));
+        assertThat(hazeList.lSet(List.of("", "key1", "-", "hej"))).isEqualTo("-Err invalid index\r\n");
+}
+    @Test
+    void callingLindexWithIndexOutOfBoundsReturnNil(){
         hazeList.rPush(List.of("", "key2", "val1", "val2", "val3"));
-        assertThat(hazeList.lIndex(List.of("", "key2", "-1"))).isEqualTo("$4\r\nval3\r\n");
+        assertThat(hazeList.lIndex(List.of("", "key2", "3"))).isEqualTo("$5\r\n(nil)\r\n");
     }
 
+
     @Test
     void callingLindexWithValidIndexZeroReturnFirstValue(){
         hazeList.rPush(List.of("", "key2", "val1", "val2", "val3"));
         assertThat(hazeList.lIndex(List.of("", "key2", "0"))).isEqualTo("$4\r\nval1\r\n");
+
     }
 }
diff --git a/src/test/java/org/fungover/haze/integration/HazeIT.java b/src/test/java/org/fungover/haze/integration/HazeIT.java
index b27a893e..cc17e725 100644
--- a/src/test/java/org/fungover/haze/integration/HazeIT.java
+++ b/src/test/java/org/fungover/haze/integration/HazeIT.java
@@ -89,17 +89,25 @@ void listKeyWithMultipleValues() {
         pool.del("test");
         assertThat(pool.exists("right")).isFalse();
     }
+        @Test
+    void listLset(){
+            pool.set("test","OK");
+            assertThat(pool.lset("test", 0, "hej")).isEqualTo("OK");
+            assertThat(pool.exists("test")).isTrue();
+            pool.del("test");
+    }
+
+
 
     @Test
     void lindexReturnCorrectIndex() {
-        assertThat(pool.rpush("test", "hello")).isEqualTo(1);
+        assertThat(pool.rpush("test", "hello")).isEqualTo(1) ;
         assertThat(pool.rpush("test", "hey")).isEqualTo(2);
         assertThat(pool.rpush("test", "bonjour")).isEqualTo(3);
         assertThat(pool.rpush("test", "hej")).isEqualTo(4);
         assertThat(pool.lindex("test", 0)).isEqualTo("hello");
         assertThat(pool.lindex("test", -1)).isEqualTo("hej");
 
-
         pool.del("test");
         assertThat(pool.exists("right")).isFalse();
     }