diff --git a/highscores.txt b/highscores.txt
index 425930e..520fe3d 100644
--- a/highscores.txt
+++ b/highscores.txt
@@ -1,2 +1,2 @@
-player_name;18787
+Lukas;4985
 player1;3999
diff --git a/makefile b/makefile
index ebcaa37..e0e6a70 100644
--- a/makefile
+++ b/makefile
@@ -35,7 +35,9 @@ $(program_obj_filesobj_files): %.o: %.c
 # --------------------------
 # Unit Tests
 # --------------------------
-unitTests:
+stackTests: stack.o test_stack.c $(unityfolder)/unity.c
+	$(CC) $(CFLAGS) -I$(unityfolder) -o runStackTests test_stack.c stack.o $(unityfolder)/unity.c
+
 	echo "needs to be implemented"
 numbersTests: numbers.o numbersTests.c $(unityfolder)/unity.c
 	$(CC) $(CFLAGS) -I$(unityfolder) -o runNumbersTests numbersTests.c numbers.o $(unityfolder)/unity.c
diff --git a/stack.c b/stack.c
index e3a90d4..61c4c01 100644
--- a/stack.c
+++ b/stack.c
@@ -10,6 +10,22 @@
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data)
 {
+    if(!(stack)) { // check if stack is empty
+        stack = malloc(sizeof(StackNode));
+        if(!stack)
+            return NULL;
+        stack->stackData = data;
+        stack->below = NULL;
+        return stack;
+    }
+
+    StackNode* newStack = malloc(sizeof(StackNode));
+        if(!newStack)
+            return stack;
+    newStack->below = stack;
+    newStack->stackData = data;
+    stack = newStack;
+    return stack;
 
 }
 
@@ -17,17 +33,32 @@ StackNode *push(StackNode *stack, void *data)
 // freed by caller.)
 StackNode *pop(StackNode *stack)
 {
-
+    if(stack) {
+        StackNode* temp = stack;
+        stack = stack->below;
+        temp->stackData = NULL;
+        free(temp);
+        temp = NULL;
+        return stack;
+    } else {
+        return NULL;
+    }
 }
 
 // Returns the data of the top element.
 void *top(StackNode *stack)
 {
+    if(stack)
+        return stack->stackData;
+    else
+        return NULL;
 
 }
 
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack)
 {
+    while(stack)
+        stack = pop(stack);
 
 }
\ No newline at end of file
diff --git a/stack.h b/stack.h
index f7d542d..faab5e5 100644
--- a/stack.h
+++ b/stack.h
@@ -9,6 +9,11 @@ The latest element is taken from the stack. */
 
 //TODO: passenden Datentyp als struct anlegen
 
+typedef struct StackNode {
+    struct StackNode* below;
+    void* stackData;
+} StackNode;
+
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data);
 
diff --git a/test_stack.c b/test_stack.c
new file mode 100644
index 0000000..79d85cc
--- /dev/null
+++ b/test_stack.c
@@ -0,0 +1,97 @@
+#include "stack.h"
+#include "unity.h"
+
+
+void test_firstNodeAddedCorrectly(void) {
+    printf("\nStarting first test...\n");
+    StackNode* modelStack = malloc(sizeof(StackNode));
+    int modelData = 5;
+    modelStack->below = NULL;
+    modelStack->stackData = &modelData;
+
+    StackNode* testStack = NULL;
+    int testData = 5;
+    testStack = push(testStack, &testData);
+    TEST_ASSERT_EQUAL_INT(*(int*)modelStack->stackData, *(int*)testStack->stackData);
+    TEST_ASSERT_NULL(testStack->below);
+    clearStack(modelStack);
+    clearStack(testStack);
+}
+
+void test_topReturnsCorrectValues(void) {
+    printf("Starting second test...\n");
+    StackNode* testStack = NULL;
+    int data1 = 1;
+    testStack = push(testStack, &data1);
+	int* returnData1 = (int*) top(testStack);
+    int data2 = 0;
+    testStack = push(testStack, &data2);
+	int* returnData2 = (int*) top(testStack);
+    int data3 = 3;
+    testStack = push(testStack, &data3);
+	int* returnData3 = (int*) top(testStack);
+
+	size_t counter = 0;
+    if(*returnData1 == 1)
+		counter++;
+	if(*returnData2 == 0)
+		counter++;
+	if(*returnData3 == 3)
+		counter++;
+    TEST_ASSERT_EQUAL_INT(3, counter);
+    clearStack(testStack);
+}
+
+void test_popRemovesCorrectly(void) {
+	printf("Starting third test...\n");
+    StackNode* testStack = NULL;
+    int data1 = 1;
+    testStack = push(testStack, &data1);
+    int data2 = 0;
+    testStack = push(testStack, &data2);
+    int data3 = 3;
+    testStack = push(testStack, &data3);
+	int data4 = 9;
+	testStack = push(testStack, &data4);
+
+	int* returnData1 = (int*) top(testStack);
+	testStack = pop(testStack);
+	int* returnData2 = (int*) top(testStack);
+	testStack = pop(testStack);
+	int* returnData3 = (int*) top(testStack);
+	testStack = pop(testStack);
+	int* returnData4 = (int*) top(testStack);
+	testStack = pop(testStack);
+
+	size_t counter = 0;
+    if(*returnData1 == 9)
+		counter++;
+	if(*returnData2 == 3)
+		counter++;
+	if(*returnData3 == 0)
+		counter++;
+	if(*returnData4 == 1)
+		counter++;
+    TEST_ASSERT_EQUAL_INT(4, counter);
+    clearStack(testStack);
+}
+
+void setUp(void) {
+
+}
+
+void tearDown(void) {
+
+}
+
+int main(void) {
+
+    UNITY_BEGIN();
+
+    printf("\n----------------------------Stack-Tests----------------------------\n");
+    RUN_TEST(test_firstNodeAddedCorrectly);
+    RUN_TEST(test_topReturnsCorrectValues);
+	RUN_TEST(test_popRemovesCorrectly);
+
+    return UNITY_END();
+}
\ No newline at end of file