diff --git a/bintree.c b/bintree.c
index 5cf82a9..a07d6e0 100644
--- a/bintree.c
+++ b/bintree.c
@@ -1,36 +1,119 @@
-#include <string.h>
-#include "stack.h"
 #include "bintree.h"
+#include "stack.h"
+#include <string.h>
 
-//TODO: binären Suchbaum implementieren
+// TODO: binären Suchbaum implementieren
 /*  * `addToTree`: fügt ein neues Element in den Baum ein (rekursiv),
-    * `clearTree`: gibt den gesamten Baum frei (rekursiv),
-    * `treeSize`: zählt die Knoten im Baum (rekursiv),
-    * `nextTreeData`: Traversierung mit Hilfe des zuvor implementierten Stacks. */
+ * `clearTree`: gibt den gesamten Baum frei (rekursiv),
+ * `treeSize`: zählt die Knoten im Baum (rekursiv),
+ * `nextTreeData`: Traversierung mit Hilfe des zuvor implementierten Stacks. */
 
-// Adds a copy of data's pointer destination to the tree using compareFct for ordering. Accepts duplicates
-// if isDuplicate is NULL, otherwise ignores duplicates and sets isDuplicate to 1 (or to 0 if a new entry is added).
-TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFctType compareFct, int *isDuplicate)
-{
+// typedef int (*CompareFctType)(const void *arg1, const void *arg2);
+//  Adds a copy of data's pointer destination to the tree using compareFct for
+//  ordering. Accepts duplicates if isDuplicate is NULL, otherwise ignores
+//  duplicates and sets isDuplicate to 1 (or to 0 if a new entry is added).
 
+void copyData(void *dest, const void *src, size_t size) {
+  unsigned char *d = dest;
+  const unsigned char *s = src;
+  for (size_t i = 0; i < size; i++) {
+    d[i] = s[i];
+  }
 }
 
-// Iterates over the tree given by root. Follows the usage of strtok. If tree is NULL, the next entry of the last tree given is returned in ordering direction.
-// Use your implementation of a stack to organize the iterator. Push the root node and all left nodes first. On returning the next element,
-// push the top node and push all its left nodes.
-void *nextTreeData(TreeNode *root)
-{
+TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize,
+                    CompareFctType compareFct, int *isDuplicate) {
 
+  // isDuplicate initialisieren (auf 0 setzen)
+  if (isDuplicate) {
+    *isDuplicate = 0;
+  }
+
+  // leerer Baum
+  if (root == NULL) {
+    TreeNode *node = malloc(sizeof(TreeNode));
+    node->data = malloc(dataSize);
+    copyData(node->data, data, dataSize);
+    node->left = NULL;
+    node->right = NULL;
+    return node;
+  }
+
+  // mit compareFct <0 links >0 rechts =0 Duplikat
+  int cmp = compareFct(data, root->data);
+
+  if (cmp < 0) {
+    root->left = addToTree(root->left, data, dataSize, compareFct, isDuplicate);
+  } else if (cmp > 0) {
+    root->right =
+        addToTree(root->right, data, dataSize, compareFct, isDuplicate);
+  } else {
+    // isDuplicate auf 1 setzen
+    if (isDuplicate) {
+      *isDuplicate = 1;
+    }
+  }
+  return root;
+}
+
+// Iterates over the tree given by root. Follows the usage of strtok. If tree is
+// NULL, the next entry of the last tree given is returned in ordering
+// direction. Use your implementation of a stack to organize the iterator. Push
+// the root node and all left nodes first. On returning the next element, push
+// the top node and push all its left nodes.
+void *nextTreeData(TreeNode *root) {
+  static StackNode *stack = NULL;
+
+  // Neue Iteration starten
+  if (root != NULL) {
+    clearStack(&stack);
+
+    TreeNode *curr = root;
+    while (curr != NULL) {
+      StackNode *oldStack = stack;
+      StackNode *newStack = push(stack, curr);
+      if (newStack == oldStack)
+        return NULL; // push fehlgeschlagen
+      stack = newStack;
+      curr = curr->left;
+    }
+  }
+  if (stack == NULL)
+    return NULL; // alles durchlaufen
+
+  // Oberstes Element abrufen
+  TreeNode *node = (TreeNode *)top(stack);
+  stack = pop(stack);
+
+  // Rechten Teilbaum pushen
+  TreeNode *curr = node->right;
+  while (curr != NULL) {
+    StackNode *oldStack = stack;
+    StackNode *newStack = push(stack, curr);
+    if (newStack == oldStack)
+      return NULL; // push fehlgeschlagen
+    stack = newStack;
+    curr = curr->left;
+  }
+  return node->data;
 }
 
 // Releases all memory resources (including data copies).
-void clearTree(TreeNode *root)
-{
+void clearTree(TreeNode *root) {
+  if (root == NULL)
+    return;
 
+  clearTree(root->left);
+  clearTree(root->right);
+
+  free(root->data);
+  free(root);
 }
 
 // Returns the number of entries in the tree given by root.
-unsigned int treeSize(const TreeNode *root)
-{
+unsigned int treeSize(const TreeNode *root) {
 
+  if (root == NULL)
+    return 0;
+  return 1 + treeSize(root->left) + treeSize(root->right);
 }
\ No newline at end of file
diff --git a/bintree.h b/bintree.h
index 25e16b2..1ced26b 100644
--- a/bintree.h
+++ b/bintree.h
@@ -5,19 +5,24 @@
 
 typedef int (*CompareFctType)(const void *arg1, const void *arg2);
 
-typedef struct node
-{
-    void *data;
-    struct node *left;
-    struct node *right;
+typedef struct node {
+  void *data;
+  struct node *left;
+  struct node *right;
 } TreeNode;
 
-// Adds a copy of data's pointer destination to the tree using compareFct for ordering. Accepts duplicates 
-// if isDuplicate is NULL, otherwise ignores duplicates and sets isDuplicate to 1 (or to 0 if a new entry is added).
-TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize, CompareFctType compareFct, int *isDuplicate);
-// Iterates over the tree given by root. Follows the usage of strtok. If tree is NULL, the next entry of the last tree given is returned in ordering direction.
-// Use your implementation of a stack to organize the iterator. Push the root node and all left nodes first. On returning the next element, 
-// push the top node and push all its left nodes.
+void copyData(void *dest, const void *src, size_t size);
+
+// Adds a copy of data's pointer destination to the tree using compareFct for
+// ordering. Accepts duplicates if isDuplicate is NULL, otherwise ignores
+// duplicates and sets isDuplicate to 1 (or to 0 if a new entry is added).
+TreeNode *addToTree(TreeNode *root, const void *data, size_t dataSize,
+                    CompareFctType compareFct, int *isDuplicate);
+// Iterates over the tree given by root. Follows the usage of strtok. If tree is
+// NULL, the next entry of the last tree given is returned in ordering
+// direction. Use your implementation of a stack to organize the iterator. Push
+// the root node and all left nodes first. On returning the next element, push
+// the top node and push all its left nodes.
 void *nextTreeData(TreeNode *root);
 // Releases all memory resources (including data copies).
 void clearTree(TreeNode *root);
diff --git a/highscores.txt b/highscores.txt
index ca5950d..2924551 100644
--- a/highscores.txt
+++ b/highscores.txt
@@ -1,2 +1,10 @@
+Kristin;9944
+Kristin;7947
+Kristin;6962
+Kristin;5987
+Kristin;5975
 krisp;4986
+krisp;4985
+Kristin;4972
 player1;3999
+Kristin;3992
diff --git a/makefile b/makefile
index 20256ce..a0cba60 100644
--- a/makefile
+++ b/makefile
@@ -25,28 +25,49 @@ doble_initial:
 # --------------------------
 # Selbst implementiertes Programm bauen
 # --------------------------
+# alle Objektdateien
 program_obj_files = stack.o bintree.o numbers.o timer.o highscore.o
-
+# alle ausführbaren Dateien zu ausführbarem Programm linken
 doble : main.o $(program_obj_files)
 	$(CC) $(FLAGS) $^ -o doble
-
+# Regel Kompilieren allgemein
 $(program_obj_files): %.o: %.c
 	$(CC) -c $(FLAGS) $^ -o $@
 
 # --------------------------
 # Unit Tests
 # --------------------------
-unitTests:
-TEST_BIN = runTests
 
-unitTests: stack.o test_stack.o
-	$(CC) $(FLAGS) $(ASAN_FLAGS) -I$(unityfolder) -o $(TEST_BIN) stack.o test_stack.o $(unityfolder)/unity.c
+STACK_TEST_BIN   = runStackTests
+NUMBERS_TEST_BIN = runNumbersTests
+BINARY_TEST_BIN  = runBinaryTests
+
+# --- Stack Tests ---
+stackTests: stack.o test_stack.o
+	$(CC) $(FLAGS) -I$(unityfolder) -o $(STACK_TEST_BIN) stack.o test_stack.o $(unityfolder)/unity.c
 
 test_stack.o: test_stack.c
 	$(CC) $(FLAGS) -I$(unityfolder) -c test_stack.c -o test_stack.o
 
+
+# --- Numbers Tests ---
+numbersTests: numbers.o bintree.o stack.o test_numbers.o
+	$(CC) $(FLAGS) -I$(unityfolder) -o $(NUMBERS_TEST_BIN) numbers.o bintree.o stack.o test_numbers.o $(unityfolder)/unity.c
+
+test_numbers.o: test_numbers.c
+	$(CC) $(FLAGS) -I$(unityfolder) -c test_numbers.c -o test_numbers.o
+
+
+# --- Binary Tree Tests ---
+binaryTests: bintree.o stack.o test_binary.o
+	$(CC) $(FLAGS) -I$(unityfolder) -o $(BINARY_TEST_BIN) bintree.o stack.o test_binary.o $(unityfolder)/unity.c
+
+test_binary.o: test_binary.c
+	$(CC) $(FLAGS) -I$(unityfolder) -c test_binary.c -o test_binary.o
+
+
 # --------------------------
 # Clean
 # --------------------------
 clean:
-	rm -f *.o doble
\ No newline at end of file
+	rm -f *.o doble $(STACK_TEST_BIN) $(NUMBERS_TEST_BIN) $(BINARY_TEST_BIN)
\ No newline at end of file
diff --git a/numbers.c b/numbers.c
index f59d9a2..414a4a4 100644
--- a/numbers.c
+++ b/numbers.c
@@ -1,26 +1,91 @@
-#include <stdlib.h>
-#include <stdio.h>
-#include <time.h>
-#include <string.h>
 #include "numbers.h"
 #include "bintree.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
 
-//TODO: getDuplicate und createNumbers implementieren
-/*  *   * Erzeugen eines Arrays mit der vom Nutzer eingegebenen Anzahl an Zufallszahlen.
-  * Sicherstellen, dass beim Befüllen keine Duplikate entstehen.
-  * Duplizieren eines zufälligen Eintrags im Array.
-  * in `getDuplicate()`: Sortieren des Arrays und Erkennen der doppelten Zahl durch Vergleich benachbarter Elemente. */
-
-// Returns len random numbers between 1 and 2x len in random order which are all different, except for two entries.
-// Returns NULL on errors. Use your implementation of the binary search tree to check for possible duplicates while
-// creating random numbers.
-unsigned int *createNumbers(unsigned int len)
-{
+int compareUnsignedInt(const void *a, const void *b) {
+  unsigned int x = *(unsigned int *)a;
+  unsigned int y = *(unsigned int *)b;
 
+  if (x < y)
+    return -1;
+  if (x > y)
+    return 1;
+  return 0;
 }
 
-// Returns only the only number in numbers which is present twice. Returns zero on errors.
-unsigned int getDuplicate(const unsigned int numbers[], unsigned int len)
-{
+// TODO: getDuplicate und createNumbers implementieren
+/**Erzeugen eines Arrays mit der vom Nutzer eingegebenen Anzahl an
+ * Zufallszahlen. Sicherstellen, dass beim Befüllen keine Duplikate entstehen.
+ * Duplizieren eines zufälligen Eintrags im Array.
+ * in `getDuplicate()`: Sortieren des Arrays und Erkennen der doppelten Zahl
+ * durch Vergleich benachbarter Elemente. */
 
-}
\ No newline at end of file
+// Returns len random numbers between 1 and 2x len in random order which are all
+// different, except for two entries. Returns NULL on errors. Use your
+// implementation of the binary search tree to check for possible duplicates
+// while creating random numbers.
+unsigned int *createNumbers(unsigned int len) {
+  if (len < 2)
+    return NULL;
+
+  unsigned int *arr = malloc(sizeof(unsigned int) * len);
+  if (!arr)
+    return NULL;
+
+  TreeNode *root = NULL;
+  srand((unsigned int)time(NULL));
+
+  for (unsigned int i = 0; i < len - 1; i++) {
+    unsigned int num;
+    int isDuplicate;
+
+    do {
+      num = (rand() % (2 * len)) + 1;
+      isDuplicate = 0;
+
+      root = addToTree(root, &num, sizeof(unsigned int), compareUnsignedInt,
+                       &isDuplicate);
+
+    } while (isDuplicate); // nur akzeptieren, wenn eindeutig
+
+    arr[i] = num;
+  }
+
+  // Jetzt gezielt EIN Duplikat erzeugen
+  unsigned int duplicateIndex = rand() % (len - 1);
+  arr[len - 1] = arr[duplicateIndex];
+
+  clearTree(root);
+  return arr;
+}
+
+// Returns only the only number in numbers which is present twice. Returns zero
+// on errors.
+unsigned int getDuplicate(const unsigned int numbers[], unsigned int len) {
+  if (!numbers || len < 2)
+    return 0;
+
+  unsigned int *copy = malloc(sizeof(unsigned int) * len);
+  if (!copy)
+    return 0;
+
+  memcpy(copy, numbers, sizeof(unsigned int) * len);
+
+  // Sortierung
+  qsort(copy, len, sizeof(unsigned int), compareUnsignedInt);
+
+  // Duplikat finden: zwei gleiche nebeneinander
+  unsigned int duplicate = 0;
+  for (unsigned int i = 0; i < len - 1; i++) {
+    if (copy[i] == copy[i + 1]) {
+      duplicate = copy[i];
+      break;
+    }
+  }
+
+  free(copy);
+  return duplicate;
+}
diff --git a/stack.c b/stack.c
index 5cd0d1a..f2b1d23 100644
--- a/stack.c
+++ b/stack.c
@@ -6,6 +6,7 @@
 
   void *data;
   struct StackNode *next;
+  struct StackNode *prev;
 
 } StackNode;*/
 
@@ -15,71 +16,85 @@
  * `top`: liefert das oberste Element zurück,
  * `clearStack`: gibt den gesamten Speicher frei. */
 
-StackNode *createNode(void *data)
-{
+// [A] -> [B] -> [C] -> NULL
+// stack -> stack.next
 
-    StackNode *node =
-        malloc(sizeof(StackNode)); // Speicher reservieren, Speicherplatz für das
-                                   // struct StackNode
+// Funktion zum erstellen neuer nodes
+StackNode *createNode(void *data) {
+  // Speicher reservieren
+  StackNode *node = malloc(sizeof(StackNode));
+  // Speicher konnte nicht reserviert werden
+  if (node == NULL)
+    return NULL;
 
-    if (node == NULL)
-        return NULL; // Speicher konnte nicht reserviert werden
+  node->data = data;
+  node->next = NULL;
+  node->prev = NULL;
 
-    node->data = data; // Zeiger auf data neuer node
-    node->next = NULL; // nächster Zeiger ist NULL, Ende der Liste
-
-    return node; // pointer auf den neuen Knoten zurückgeben
+  return node;
 }
 
 // Pushes data as pointer onto the stack.
-StackNode *push(StackNode *stack, void *data)
-{
-    StackNode *newNode = createNode(data); // Speicher für neuen Knoten
-                                           // reservieren
+StackNode *push(StackNode *stack, void *data) {
 
-    if (newNode == NULL)
-    { // wenn Speicher nicht reserviert werden konnte, wird
-        // stack unverändert zurückgegeben
-        return stack;
-    }
+  StackNode *newNode = createNode(data);
 
-    newNode->next = stack; // pointer verschieben
+  // Fehler beim Reservieren des Speichers, stack wird unverändert zurückgegeben
+  if (newNode == NULL) {
+    return stack;
+  }
 
-    return newNode; // Zeiger auf neuen Speicherbereich zurückgeben
+  // der aktuelle Kopf wird der nächste Node
+  newNode->next = stack;
+
+  // bisheriger Kopf bekommt Pointer auf oberstes Element
+  if (stack != NULL) {
+    stack->prev = newNode;
+  }
+
+  return newNode; // neuer Kopf wird zurückgegeben
 }
 
-// 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)
-{
-    if (stack == NULL)
-        return NULL;
+// 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 *nextNode = stack->next;
+  // Stack ohne Elemente
+  if (stack == NULL)
+    return NULL;
+
+  // Element unter Kopf wird als nextNode gespeichert
+  StackNode *nextNode = stack->next;
+  if (nextNode != NULL) {
+    nextNode->prev = NULL; // der Zeiger zum Kopf wird auf NULL gesetzt
+  }
 
     free(stack);
 
-    stack = NULL;
+  stack = NULL; // Speicher des Kopfes freigeben
 
-    return nextNode;
+  return nextNode; // neuen Kopf zurückgeben
 }
 
 // Returns the data of the top element.
-void *top(StackNode *stack) { return stack != NULL ? stack->data : NULL; }
+void *top(StackNode *stack) {
+  // wenn stack leer ist, wird NULL zurückgegeben
+  // Zeiger auf Daten des obersten Elements
+  return stack ? stack->data : NULL;
+}
 
 // Clears stack and releases all memory.
-void clearStack(StackNode **stack)
-{
-    while (*stack != NULL)
-    {
+void clearStack(StackNode **stack) { // Zeiger auf den Zeiger auf den Stackkopf
+  // verändert den Zeiger selbst, mit *stack lokale Kopie
+  // im Aufruf &stack verwenden
+  while (*stack != NULL) {
 
-        StackNode *next = (*stack)->next;
-        free(*stack);
-        (*stack)->data = NULL;
-        (*stack)->next = NULL;
-        (*stack)->prev = NULL;
-        (*stack) = next;
+    (*stack)->prev = NULL;            // späteren Pointerzugriff verhindern
+    StackNode *next = (*stack)->next; // nächstes Element speichern
 
-    }
-    
+    (*stack)->next = NULL; // späteren Pointerzugriff verhindern
+
+    free(*stack);  // aktuelles Element freigeben
+    *stack = next; // Zeiger auf nächsten Knoten setzen
+  }
 }
\ No newline at end of file
diff --git a/stack.h b/stack.h
index 8119b2c..bbb3fce 100644
--- a/stack.h
+++ b/stack.h
@@ -19,16 +19,6 @@ typedef struct StackNode {
 
 StackNode *createNode(void *data);
 
-typedef struct StackNode {
-
-  void *data;
-  struct StackNode *next;
-  struct StackNode *prev;
-
-} StackNode;
-
-StackNode *createNode(void *data);
-
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data);
 
diff --git a/test_binary.c b/test_binary.c
new file mode 100644
index 0000000..a0d9cbc
--- /dev/null
+++ b/test_binary.c
@@ -0,0 +1,105 @@
+#include "unity.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "bintree.h"
+int compareUnsignedInt(const void *a, const void *b) {
+  unsigned int x = *(unsigned int *)a;
+  unsigned int y = *(unsigned int *)b;
+
+  if (x < y)
+    return -1;
+  if (x > y)
+    return 1;
+  return 0;
+}
+
+TreeNode *root = NULL;
+
+void setUp(void) {
+  root = NULL; // vor jedem Test leeren
+}
+
+void tearDown(void) { clearTree(root); }
+
+// Test, ob addToTree Knoten korrekt hinzufügt
+void test_addToTree_basic(void) {
+  int isDup;
+  unsigned int val = 10;
+  root = addToTree(root, &val, sizeof(val), compareUnsignedInt, &isDup);
+  TEST_ASSERT_NOT_NULL(root);
+  TEST_ASSERT_EQUAL_UINT(10, *(unsigned int *)root->data);
+  TEST_ASSERT_EQUAL_INT(0, isDup);
+  TEST_ASSERT_EQUAL_UINT(1, treeSize(root));
+}
+
+// Test, dass Duplikate erkannt werden
+void test_addToTree_duplicate(void) {
+  int isDup;
+  unsigned int val1 = 10, val2 = 10;
+  root = addToTree(root, &val1, sizeof(val1), compareUnsignedInt, &isDup);
+  TEST_ASSERT_EQUAL_INT(0, isDup);
+  root = addToTree(root, &val2, sizeof(val2), compareUnsignedInt, &isDup);
+  TEST_ASSERT_EQUAL_INT(1, isDup);
+  TEST_ASSERT_EQUAL_UINT(1, treeSize(root)); // Duplikate nicht hinzufügen
+}
+
+// Test nextTreeData Traversierung
+void test_nextTreeData_in_order(void) {
+  unsigned int values[] = {20, 10, 30};
+  int isDup;
+  for (int i = 0; i < 3; i++) {
+    root = addToTree(root, &values[i], sizeof(values[i]), compareUnsignedInt,
+                     &isDup);
+  }
+
+  unsigned int expected[] = {10, 20, 30};
+  int idx = 0;
+  void *data;
+
+  // **Neue Iteration starten**
+  data = nextTreeData(root);
+  while (data != NULL) {
+    TEST_ASSERT_EQUAL_UINT(expected[idx], *(unsigned int *)data);
+    idx++;
+    data = nextTreeData(NULL); // weitere Elemente abrufen
+  }
+
+  TEST_ASSERT_EQUAL_INT(3, idx); // alle 3 Knoten besucht
+}
+
+// Test clearTree gibt Speicher frei
+void test_clearTree(void) {
+  unsigned int val = 42;
+  int isDup;
+  root = addToTree(root, &val, sizeof(val), compareUnsignedInt, &isDup);
+  clearTree(root);
+  root = NULL; // clearTree löscht nicht die root-Variable selbst
+  TEST_ASSERT_NULL(root);
+}
+
+// Test treeSize zählt korrekt
+void test_treeSize(void) {
+  unsigned int vals[] = {10, 20, 5};
+  int isDup;
+  for (int i = 0; i < 3; i++) {
+    root =
+        addToTree(root, &vals[i], sizeof(vals[i]), compareUnsignedInt, &isDup);
+  }
+  TEST_ASSERT_EQUAL_UINT(3, treeSize(root));
+}
+
+int main(void) {
+  UNITY_BEGIN();
+
+  printf(
+      "\n------------------------binarytree test------------------------\n\n");
+
+  RUN_TEST(test_addToTree_basic);
+  RUN_TEST(test_addToTree_duplicate);
+  RUN_TEST(test_nextTreeData_in_order);
+  RUN_TEST(test_clearTree);
+  RUN_TEST(test_treeSize);
+  return UNITY_END();
+}
\ No newline at end of file
diff --git a/test_numbers.c b/test_numbers.c
new file mode 100644
index 0000000..8992bb8
--- /dev/null
+++ b/test_numbers.c
@@ -0,0 +1,61 @@
+#include "unity.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "numbers.h"
+
+#define TEST_ARRAY_LEN 100
+
+void test_createNumbers_length(void) {
+  unsigned int *arr = createNumbers(TEST_ARRAY_LEN);
+  TEST_ASSERT_NOT_NULL(arr);
+  free(arr);
+}
+
+void test_createNumbers_single_duplicate(void) {
+  unsigned int *arr = createNumbers(TEST_ARRAY_LEN);
+  TEST_ASSERT_NOT_NULL(arr);
+
+  unsigned int duplicate = getDuplicate(arr, TEST_ARRAY_LEN);
+  TEST_ASSERT_TRUE(duplicate > 0);
+
+  unsigned int count = 0;
+  for (unsigned int i = 0; i < TEST_ARRAY_LEN; i++) {
+    if (arr[i] == duplicate) {
+      count++;
+    }
+  }
+  TEST_ASSERT_EQUAL_UINT(2, count);
+
+  free(arr);
+}
+
+void test_getDuplicate_manual_array(void) {
+  unsigned int numbers[5] = {10, 20, 30, 40, 20};
+  unsigned int dup = getDuplicate(numbers, 5);
+  TEST_ASSERT_EQUAL_UINT(20, dup);
+}
+
+void test_getDuplicate_invalid_input(void) {
+  TEST_ASSERT_EQUAL_UINT(0, getDuplicate(NULL, 5));
+  unsigned int arr[1] = {42};
+  TEST_ASSERT_EQUAL_UINT(0, getDuplicate(arr, 1));
+}
+
+void setUp(void) {}
+void tearDown(void) {}
+
+int main(void) {
+
+  UNITY_BEGIN();
+
+  printf("\n------------------------numbers test------------------------\n\n");
+
+  RUN_TEST(test_createNumbers_length);
+  RUN_TEST(test_createNumbers_single_duplicate);
+  RUN_TEST(test_getDuplicate_manual_array);
+  RUN_TEST(test_getDuplicate_invalid_input);
+
+  return UNITY_END();
+}
diff --git a/test_stack.c b/test_stack.c
index a9f9914..ee3a6e5 100644
--- a/test_stack.c
+++ b/test_stack.c
@@ -5,40 +5,124 @@
 
 #include "stack.h"
 
+// StackNode *createNode(void *data) testen
 void test_createNode(void) {
 
   int testInt = 26;
+  StackNode *testNode = createNode(&testInt); // Adresse des testInts
 
-  StackNode *testNode = createNode(&testInt);
+  TEST_ASSERT_NOT_NULL(
+      testNode); // Speicher konnte reserviert werden, malloc ist nicht NULL
+  TEST_ASSERT_EQUAL_PTR(&testInt, testNode->data); // data pointer gesetzt
+  TEST_ASSERT_NULL(testNode->next); // vorheriger und nächster Eintrag NULL
+  TEST_ASSERT_NULL(testNode->prev);
 
-  TEST_ASSERT_NOT_NULL(testNode);
-
-  TEST_ASSERT_EQUAL_PTR(&testInt, testNode->data);
-
-  TEST_ASSERT_NULL(testNode->next);
-
-  free(testNode);
+  free(testNode); // Speicher freigeben
 }
 
-void test_pushDataToStack(void) {}
+// StackNode *push(StackNode *stack, void *data) testen
+void test_pushDataToStack(void) {
 
-void test_deleteTopElement(void) {}
+  int testInts[] = {27, 28};
 
-void test_returnData(void) {}
+  StackNode *testStack = NULL; // leeren testStack initialisieren
+
+  testStack =
+      push(testStack, &testInts[0]); // leerer Stack mit Adresse des testInts
+
+  TEST_ASSERT_NOT_NULL(testStack); // im Fehlerfall wird testStack unverändert
+                                   // zurückgegeben -> bei Fehler NULL
+  TEST_ASSERT_EQUAL_PTR(&testInts[0], testStack->data); // data pointer gesetzt
+  TEST_ASSERT_NULL(testStack->next); // vorheriger und nächster pointer auf NULL
+                                     // gesetzt, da es nur einen Knoten gibt
+  TEST_ASSERT_NULL(testStack->prev);
+
+  // zweiter Push
+  StackNode *oldHead = testStack; // bisherigen head speichern
+  testStack = push(testStack, &testInts[1]);
+
+  TEST_ASSERT_NOT_NULL(testStack);
+  TEST_ASSERT_NOT_EQUAL(
+      oldHead,
+      testStack); // bei malloc Fehler wird der head unverändert zurückgegeben
+
+  TEST_ASSERT_EQUAL_PTR(&testInts[0],
+                        oldHead->data); // data pointer wurden richtig gesetzt
+  TEST_ASSERT_EQUAL_PTR(&testInts[1], testStack->data);
+
+  // richtige Verkettung: NULL <- testStack -> testStack->next -> oldHead ->
+  // NULL
+  TEST_ASSERT_EQUAL_PTR(oldHead, testStack->next);
+  TEST_ASSERT_EQUAL_PTR(testStack, oldHead->prev);
+  TEST_ASSERT_NULL(testStack->prev);
+
+  // Speicherfreigabe
+  testStack->next = NULL; // pointer ungültig machen, damit nicht ausversehen
+                          // später aufgerufen
+  oldHead->prev = NULL;
+
+  free(oldHead);
+  free(testStack);
+}
+
+void test_deleteTopElement(void) {
+
+  int testInts[] = {10, 20, 30};
+  StackNode *stack = NULL;
+
+  for (int i = 0; i < 3;
+       i++) { // Stack mit drei Elementen, oberestes Element mit data 30
+    stack = push(stack, &testInts[i]);
+  }
+
+  TEST_ASSERT_EQUAL_PTR(&testInts[2], stack->data); // oberstes Element ist 30
+
+  stack = pop(stack); // oberstes Element löschen
+  TEST_ASSERT_EQUAL_PTR(&testInts[1], stack->data);
+  TEST_ASSERT_NULL(
+      stack->prev); // pointer zum alten head wurde auf NULL gesetzt
+
+  stack = pop(stack);
+  TEST_ASSERT_EQUAL_PTR(&testInts[0], stack->data);
+  TEST_ASSERT_NULL(stack->prev);
+
+  stack = pop(stack); // bei leerem Stack wird NULL zurückgegeben
+  TEST_ASSERT_NULL(stack);
+}
+
+void test_returnData(void) {
+
+  int testInts[] = {10, 20, 30};
+  StackNode *stack = NULL;
+
+  for (int i = 0; i < 3; i++) {
+    stack = push(stack, &testInts[i]);
+  }
+
+  TEST_ASSERT_EQUAL_PTR(&testInts[2],
+                        top(stack)); // top gibt richtige Adresse zurück
+  stack = pop(stack);                // oberstes Element löschen
+  TEST_ASSERT_EQUAL_PTR(&testInts[1], top(stack));
+
+  stack = pop(stack);
+  TEST_ASSERT_EQUAL_PTR(&testInts[0], top(stack));
+
+  stack = pop(stack); // bei leerem Stack wird NULL zurückgegeben
+  TEST_ASSERT_NULL(stack);
+}
 
 void test_clearStack(void) {
-
   int testInts[] = {1, 2, 3, 4, 5};
-  StackNode *testStack = NULL;
+  StackNode *stack = NULL;
 
   for (int i = 0; i < 5; i++) {
-
-    testStack = push(testStack, &testInts[i]);
+    stack = push(stack, &testInts[i]);
   }
   //printf("testints: %d,%d,%d,%d,%d",testInts[0],testInts[1],testInts[2],testInts[3],testInts[4]);
 
-  clearStack(&testStack);
-  TEST_ASSERT_NULL(testStack);
+  clearStack(&stack);
+
+  TEST_ASSERT_NULL(stack);
 }
 
 void setUp(void) {}
@@ -48,13 +132,13 @@ int main(void) {
 
   UNITY_BEGIN();
 
-  printf("------------------------stack test------------------------\n");
+  printf("\n------------------------stack test------------------------\n\n");
+
   RUN_TEST(test_createNode);
   RUN_TEST(test_pushDataToStack);
   RUN_TEST(test_deleteTopElement);
   RUN_TEST(test_returnData);
   RUN_TEST(test_clearStack);
-  RUN_TEST(test_clearStack);
 
   return UNITY_END();
 }