diff --git a/makefile b/makefile
index 1f15f75..84d7bb4 100644
--- a/makefile
+++ b/makefile
@@ -29,14 +29,19 @@ program_obj_files = stack.o bintree.o numbers.o timer.o highscore.o
 doble : main.o $(program_obj_files)
 	$(CC) $(FLAGS) $^ -o doble
 
-$(program_obj_filesobj_files): %.o: %.c
-	$(CC) -c $(FLAGS) $^ -o $@
+%.o: %.c
+	$(CC) -c $(FLAGS) $< -o $@
+
 
 # --------------------------
 # Unit Tests
 # --------------------------
-unitTests:
-	echo "needs to be implemented"
+test_stack: test_stack.c stack.o
+	$(CC) $(FLAGS) test_stack.c stack.o -o test_stack.exe
+
+unitTests: test_stack
+	./test_stack.exe
+
 
 # --------------------------
 # Clean
diff --git a/stack.o b/stack.o
new file mode 100644
index 0000000..6d7ac52
Binary files /dev/null and b/stack.o differ
diff --git a/test_stack.c b/test_stack.c
index 792657f..f6f1377 100644
--- a/test_stack.c
+++ b/test_stack.c
@@ -5,6 +5,9 @@
 #include <stdlib.h>
 #include "stack.h"
 
+#define TEST(description, condition) \
+    printf("%-40s: %s\n", description, (condition) ? "OK" : "FAIL")
+
 int main(void)
 {
     StackNode *stack = NULL;
@@ -17,21 +20,33 @@ int main(void)
     *a = 10;
     *b = 20;
 
+
+    printf("Starte Unit Tests fuer Stack\n");
     stack = push(stack, a);
     stack = push(stack, b);
 
-    printf("Top sollte 20 sein, es kommt %d raus\n", *(int*)top(stack));
+    TEST("Top nach zwei Pushes == 20", *(int*)top(stack) == 20);
 
 
     // pop test
     stack = pop(stack);
-    printf("Top sollte jetzt 10 sein, es kommt %d raus\n", *(int*)top(stack));
+    TEST("Top == 10 nach Pop", *(int*)top(stack) == 10);
 
 
+    stack = pop(stack);
+    TEST("Stack leer nach zwei Pops", stack == NULL);
+
+
+
+    stack = push(stack, a);
+    stack = push(stack, b);
+
     // clearStack test
-    printf("fuehre ClearStack aus...\n");
 
     clearStack(stack);
+    stack = NULL;
+
+    TEST("clearStack ausgefuehrt (kein crash)", 1);
 
     free(a);
     free(b);
diff --git a/test_stack.exe b/test_stack.exe
index 87c27a3..f931938 100644
Binary files a/test_stack.exe and b/test_stack.exe differ