diff --git a/stack.c b/stack.c
index e4d02d2..61c4c01 100644
--- a/stack.c
+++ b/stack.c
@@ -12,12 +12,16 @@ 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;
@@ -32,7 +36,6 @@ StackNode *pop(StackNode *stack)
     if(stack) {
         StackNode* temp = stack;
         stack = stack->below;
-        free(temp->data);
         temp->stackData = NULL;
         free(temp);
         temp = NULL;
@@ -55,11 +58,7 @@ void *top(StackNode *stack)
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack)
 {
-    if(stack) {
-        do {
-            stack = pop(stack);
-        } while (stack->below);
-        pop(stack);
-    }
+    while(stack)
+        stack = pop(stack);
 
 }
\ No newline at end of file
diff --git a/stack.h b/stack.h
index d15a367..faab5e5 100644
--- a/stack.h
+++ b/stack.h
@@ -10,7 +10,7 @@ The latest element is taken from the stack. */
 //TODO: passenden Datentyp als struct anlegen
 
 typedef struct StackNode {
-    StackNode* below;
+    struct StackNode* below;
     void* stackData;
 } StackNode;
 
diff --git a/test_stack.c b/test_stack.c
index c4fe248..d21177d 100644
--- a/test_stack.c
+++ b/test_stack.c
@@ -3,18 +3,28 @@
 
 
 void test_firstNodeAddedCorrectly(void) {
-    StackNode* modelStack;
+    printf("\nStarting first test...\n");
+    StackNode* modelStack = malloc(sizeof(StackNode));
     int modelData = 5;
     modelStack->below = NULL;
-    modelStack->data = &modelData;
+    modelStack->stackData = &modelData;
 
     StackNode* testStack = NULL;
     int testData = 5;
     testStack = push(testStack, &testData);
-    TEST_ASSERT_EQUAL_INT(*(modelStack->data), *(testStack->data));
+    TEST_ASSERT_EQUAL_INT(*(int*)modelStack->stackData, *(int*)testStack->stackData);
     TEST_ASSERT_NULL(testStack->below);
+    clearStack(modelStack);
+    clearStack(testStack);
 }
 
+void setUp(void) {
+
+}
+
+void tearDown(void) {
+
+}
 
 int main(void) {