diff --git a/.vscode/settings.json b/.vscode/settings.json
new file mode 100644
index 0000000..f36e144
--- /dev/null
+++ b/.vscode/settings.json
@@ -0,0 +1,6 @@
+{
+    "files.associations": {
+        "stdio.h": "c",
+        "stdlib.h": "c"
+    }
+}
\ No newline at end of file
diff --git a/makefile b/makefile
index 5b2e04b..49f367b 100644
--- a/makefile
+++ b/makefile
@@ -37,6 +37,8 @@ doble_initial:
 # --------------------------
 # Unit Tests
 # --------------------------
+stackTests: stack.o test_stack.c $(unityfolder)/unity.c
+	$(CC) $(CFLAGS) -I$(unityfolder) -o stackTests test_stack.c stack.o $(unityfolder)/unity.c ${LDFLAGS}
 unitTests:
 	echo "needs to be implemented"
 
diff --git a/stack.c b/stack.c
index e3a90d4..1814599 100644
--- a/stack.c
+++ b/stack.c
@@ -8,26 +8,53 @@
     * `clearStack`: gibt den gesamten Speicher frei. */
 
 // Pushes data as pointer onto the stack.
-StackNode *push(StackNode *stack, void *data)
+StackNode* push(StackNode* stack, void* data)
 {
-
+    //pointer onto new struct
+   StackNode* newNode = malloc(sizeof(StackNode));
+   newNode->data = data;
+    //*stack := first node of the stack; is now the second to first node
+   newNode->nextNode = stack;
+    return newNode;
 }
 
 // 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* pop(StackNode* stack)
 {
+    //getting the second to first node
+    StackNode* tmp = stack->nextNode;
 
+    // data should be freed by the caller
+    // free(stack->data);
+    // stack->data = NULL;
+    free(stack);
+    stack = NULL;
+
+    return tmp;
 }
 
 // Returns the data of the top element.
-void *top(StackNode *stack)
+void* top(StackNode* stack)
 {
+    //No stack --> No data-pointer
+    if (stack == NULL) return NULL;
 
+    return stack->data;
 }
 
 // Clears stack and releases all memory.
-void clearStack(StackNode *stack)
+void clearStack(StackNode* stack)
 {
+    if (stack == NULL) return;
 
+    if (stack->nextNode != NULL) clearStack(stack->nextNode);
+
+    // date should be freed by the caller.
+    // free(stack->data);
+    // stack->data = NULL;
+
+    free(stack);
+    // technically not needed (dangling pointer)
+    stack = NULL;
 }
\ No newline at end of file
diff --git a/stack.h b/stack.h
index f7d542d..4c3a3a7 100644
--- a/stack.h
+++ b/stack.h
@@ -7,17 +7,20 @@ The latest element is taken from the stack. */
 
 #include <stdlib.h>
 
-//TODO: passenden Datentyp als struct anlegen
+typedef struct StackNode {
+    void* data;
+    struct StackNode* nextNode;
+} StackNode;
 
 // Pushes data as pointer onto the stack.
-StackNode *push(StackNode *stack, void *data);
+StackNode* push(StackNode *stack, void *data);
 
 // 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* pop(StackNode *stack);
 
 // Returns the data of the top element.
-void *top(StackNode *stack);
+void* top(StackNode *stack);
 
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack);
diff --git a/stackTests b/stackTests
new file mode 100644
index 0000000..be175e3
Binary files /dev/null and b/stackTests differ
diff --git a/test_stack.c b/test_stack.c
new file mode 100644
index 0000000..9b77f35
--- /dev/null
+++ b/test_stack.c
@@ -0,0 +1,77 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include "unity.h"
+#include "stack.h"
+
+
+void test_topReturnsCorrectValue(void) {
+    // 1. Arrange
+    int* value1;
+    int* value2;
+    int* outVal1;
+    int* outVal2;
+    value1 = malloc(sizeof(int));
+    value2 = malloc(sizeof(int));
+    StackNode* startNode = NULL;
+
+    // 2. Act
+    *value1 = 1234;
+    *value2 = 5678;
+    startNode = push(startNode, value1);
+    // new top node is node 2
+    startNode = push(startNode, value2);
+    outVal2 = top(startNode);
+    // node 1 should now be the top node
+    startNode = pop(startNode);
+    outVal1 = top(startNode);
+
+    // 3. Assert
+    //Also tests for the functionality of 'push'
+    TEST_ASSERT_EQUAL_INT32(*value1, *outVal1);
+    TEST_ASSERT_EQUAL_INT32(*value2, *outVal2);
+
+    free(value1);
+    value1 = NULL;
+    free(value2);
+    value2 = NULL;
+    clearStack(startNode);
+}
+
+void test_popRemovesElements(void) {
+   // 1. Arrange
+   StackNode* startNode = NULL;
+   
+   // 2. Act
+   // Entering some Elements into Stack (could be added manually for testing)
+   startNode = push(startNode, NULL);
+   startNode = push(startNode, NULL);
+   startNode = push(startNode, NULL);
+   startNode = push(startNode, NULL);
+   // Now removing created Elements
+   startNode = pop(startNode);
+   startNode = pop(startNode);
+   startNode = pop(startNode);
+   startNode = pop(startNode);
+
+    // 3. Assert
+    TEST_ASSERT_NULL(startNode);
+}
+
+void setUp(void){
+
+}
+
+void tearDown(void){
+
+}
+
+int main(void) {
+    UNITY_BEGIN();
+
+    printf("\n============================\nStack tests\n============================\n");
+
+    RUN_TEST(test_topReturnsCorrectValue);
+    RUN_TEST(test_popRemovesElements);
+
+    return UNITY_END();
+}
\ No newline at end of file