diff --git a/doble.exe b/doble.exe
index f8de930..2db1f8d 100644
Binary files a/doble.exe and b/doble.exe differ
diff --git a/highscores.txt b/highscores.txt
index 3fe3727..d3dc2cb 100644
--- a/highscores.txt
+++ b/highscores.txt
@@ -3,6 +3,7 @@ Regis;18924
 player_name;9929
 Kamto;7946
 player_name;5987
+player_1;4989
 Warren;4986
 player_name;4983
 player1;3999
diff --git a/makefile b/makefile
index 1f15f75..ec1390d 100644
--- a/makefile
+++ b/makefile
@@ -35,8 +35,20 @@ $(program_obj_filesobj_files): %.o: %.c
 # --------------------------
 # Unit Tests
 # --------------------------
-unitTests:
-	echo "needs to be implemented"
+
+unitTests: test_numbers test_stack
+
+test_numbers: test_numbers.o stack.o bintree.o numbers.o
+	$(CC) $(FLAGS) $^ -o test_numbers
+
+test_numbers.o: test_numbers.c
+	$(CC) -c $(FLAGS) $< -o $@
+
+test_stack: test_stack.o stack.o
+	$(CC) $(FLAGS) $^ -o test_stack
+
+test_stack.o:  test_stack.c
+	$(CC) -c $(FLAGS) $< -o $@
 
 # --------------------------
 # Clean
diff --git a/numbers.c b/numbers.c
index bde8485..71541b9 100644
--- a/numbers.c
+++ b/numbers.c
@@ -15,6 +15,7 @@
 // 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;
 
@@ -52,6 +53,7 @@ unsigned int *createNumbers(unsigned int len) {
 
 // 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;
 
     // Kopie erstellen, damit Original nicht verändert wird
diff --git a/test_numbers.exe b/test_numbers.exe
index f648461..088659d 100644
Binary files a/test_numbers.exe and b/test_numbers.exe differ
diff --git a/ test_stack.c b/test_stack.c
similarity index 100%
rename from  test_stack.c
rename to test_stack.c
diff --git a/test_stack.exe b/test_stack.exe
new file mode 100644
index 0000000..7f47629
Binary files /dev/null and b/test_stack.exe differ