diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e813ee4
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+doble_initial.exe
+highscores.txt
+runStackTest.exe
+stack.o
diff --git a/makefile b/makefile
index 1f15f75..5076d63 100644
--- a/makefile
+++ b/makefile
@@ -35,8 +35,8 @@ $(program_obj_filesobj_files): %.o: %.c
 # --------------------------
 # Unit Tests
 # --------------------------
-unitTests:
-	echo "needs to be implemented"
+unitTests: stack.o test_stack.c $(unityfolder)/unity.c
+	$(CC) $(FLAGS) -I$(unityfolder) -o runStackTest test_stack.c stack.o $(unityfolder)/unity.c
 
 # --------------------------
 # Clean
diff --git a/stack.c b/stack.c
index e3a90d4..2315722 100644
--- a/stack.c
+++ b/stack.c
@@ -1,33 +1,91 @@
 #include <stdlib.h>
 #include "stack.h"
 
-//TODO: grundlegende Stackfunktionen implementieren:
+// TODO: grundlegende Stackfunktionen implementieren:
 /*  * `push`: legt ein Element oben auf den Stack,
-    * `pop`: entfernt das oberste Element,
-    * `top`: liefert das oberste Element zurück,
-    * `clearStack`: gibt den gesamten Speicher frei. */
+ * `pop`: entfernt das oberste Element,
+ * `top`: liefert das oberste Element zurück,
+ * `clearStack`: gibt den gesamten Speicher frei. */
 
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data)
 {
+    StackNode *tempNode, *newNode;
 
+    newNode = malloc(sizeof(StackNode));
+    newNode->value = *(int *)data;
+    newNode->next = NULL;
+
+    if (stack == NULL)
+    {
+        stack = newNode;
+        return stack;
+    }
+
+    tempNode = stack;
+    while (tempNode->next != NULL)
+    {
+        tempNode = tempNode->next;
+    }
+    tempNode->next = newNode;
+
+    return stack;
 }
 
 // Deletes the top element of the stack (latest added element) and releases its memory. (Pointer to data has to be
 // freed by caller.)
 StackNode *pop(StackNode *stack)
 {
+    StackNode *tempNode;
 
+    if (stack == NULL)
+    {
+        return stack;
+    }
+
+    tempNode = stack;
+    while (tempNode->next->next != NULL)
+    {
+        tempNode = tempNode->next;
+    }
+    free(tempNode->next);
+    tempNode->next = NULL;
+
+    return stack;
 }
 
 // Returns the data of the top element.
 void *top(StackNode *stack)
 {
+    StackNode *tempNode;
 
+    if (stack == NULL)
+    {
+        return NULL;
+    }
+
+    tempNode = stack;
+    while (tempNode->next != NULL)
+    {
+        tempNode = tempNode->next;
+    }
+
+    return &tempNode->value;
 }
 
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack)
 {
+    StackNode *tempNode;
 
+    if (stack == NULL)
+    {
+        return;
+    }
+
+    tempNode = stack;
+    while (tempNode != NULL)
+    {
+        tempNode = pop(tempNode);
+    }
 }
\ No newline at end of file
diff --git a/stack.h b/stack.h
index f7d542d..7019034 100644
--- a/stack.h
+++ b/stack.h
@@ -8,6 +8,10 @@ The latest element is taken from the stack. */
 #include <stdlib.h>
 
 //TODO: passenden Datentyp als struct anlegen
+typedef struct Node {
+    int value;
+    struct Node* next;
+} 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..c9b71cf
--- /dev/null
+++ b/test_stack.c
@@ -0,0 +1,67 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "stack.h"
+#include "unity.h"
+
+void test_push(void)
+{
+    StackNode *testNode;
+    int data = 1;
+
+    // Test für leeren Stack
+    testNode = push(NULL, &data);
+    TEST_ASSERT_NOT_NULL(&testNode);
+    TEST_ASSERT_NULL(testNode->next);
+    TEST_ASSERT_EQUAL_INT(1, testNode->value);
+
+    data = 2;
+
+    // Test für nicht leeren Stack
+    testNode = push(testNode, &data);
+    TEST_ASSERT_NOT_NULL(&testNode);
+    TEST_ASSERT_NOT_NULL(testNode->next);
+    TEST_ASSERT_NULL(testNode->next->next);
+    TEST_ASSERT_EQUAL_INT(1, testNode->value);
+    TEST_ASSERT_EQUAL_INT(2, testNode->next->value);
+}
+
+void test_pop(void)
+{
+    
+    TEST_ASSERT_NULL(pop(NULL));
+
+}
+
+void test_top(void)
+{
+
+    TEST_ASSERT_NULL(top(NULL));
+}
+
+void test_clear(void)
+{
+
+    // TEST_ASSERT_NULL(clearStack(NULL));
+}
+
+void setUp(void) {
+    // Falls notwendig, kann hier Vorbereitungsarbeit gemacht werden
+}
+
+void tearDown(void) {
+    // Hier kann Bereinigungsarbeit nach jedem Test durchgeführt werden
+}
+
+int main()
+{
+    UNITY_BEGIN();
+
+    printf("============================\nStack tests\n============================\n");
+
+    RUN_TEST(test_push);
+    RUN_TEST(test_pop);
+    RUN_TEST(test_top);
+    RUN_TEST(test_clear);
+
+    return UNITY_END();
+}
\ No newline at end of file
diff --git a/unittest.h b/unittest.h
new file mode 100644
index 0000000..fc327ca
--- /dev/null
+++ b/unittest.h
@@ -0,0 +1,10 @@
+#ifndef UNITTTESTS_H
+#define UNITTTESTS_H
+
+#include <stdio.h>
+
+typedef int (*UnitTestType)(void);
+
+#define RUN_UNIT_TEST(fct) printf("%80s: %d\n", #fct, fct())
+
+#endif