diff --git a/numbers.c b/numbers.c
index f59d9a2..61fa7cc 100644
--- a/numbers.c
+++ b/numbers.c
@@ -14,7 +14,7 @@
 // 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)
+unsigned int* createNumbers(unsigned int len)
 {
 
 }
diff --git a/stackTests b/stackTests
index be175e3..b799152 100644
Binary files a/stackTests and b/stackTests differ
diff --git a/test_stack.c b/test_stack.c
index 9b77f35..90bf120 100644
--- a/test_stack.c
+++ b/test_stack.c
@@ -37,6 +37,18 @@ void test_topReturnsCorrectValue(void) {
     clearStack(startNode);
 }
 
+void test_topReturnsNullOnNotExistingStack(void) {
+    // 1. Arrange
+    StackNode* startNode = NULL;
+    int* data;
+
+    // 2. Act
+    data = top(startNode);
+
+    //3. Assert
+    TEST_ASSERT_NULL(data);
+}
+
 void test_popRemovesElements(void) {
    // 1. Arrange
    StackNode* startNode = NULL;
@@ -70,6 +82,7 @@ int main(void) {
 
     printf("\n============================\nStack tests\n============================\n");
 
+    RUN_TEST(test_topReturnsNullOnNotExistingStack);
     RUN_TEST(test_topReturnsCorrectValue);
     RUN_TEST(test_popRemovesElements);