diff --git a/testStack.c b/testStack.c
index 25f89d0..88f6c82 100644
--- a/testStack.c
+++ b/testStack.c
@@ -55,12 +55,9 @@ int main(void) {
     stack = push(stack, e);
 
     clearStack(stack);
-    // stack pointer still points to old top; we must reset manually
     stack = NULL;
 
-    // no crash = success
-
-    // free remaining data
+    // free allocated ints
     free(a);
     free(b);
     free(c);
diff --git a/test_number.c b/test_number.c
index d92535b..25f89d0 100644
--- a/test_number.c
+++ b/test_number.c
@@ -1,3 +1,73 @@
-//
-// Created by kamtewil on 02.12.2025.
-//
\ No newline at end of file
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include "stack.h"
+
+// Helper: create int on heap
+static int *make_int(int value) {
+    int *p = malloc(sizeof(int));
+    if (!p) {
+        fprintf(stderr, "Memory allocation failed\n");
+        exit(1);
+    }
+    *p = value;
+    return p;
+}
+
+int main(void) {
+
+    printf("Running stack unit tests...\n");
+
+    StackNode *stack = NULL;
+
+    // --- Test 1: push() on empty stack ---
+    int *a = make_int(10);
+    stack = push(stack, a);
+    assert(stack != NULL);
+    assert(top(stack) == a);
+    assert(*(int*)top(stack) == 10);
+
+    // --- Test 2: push() on non-empty stack ---
+    int *b = make_int(20);
+    stack = push(stack, b);
+    assert(top(stack) == b);
+    assert(*(int*)top(stack) == 20);
+
+    // --- Test 3: pop() returns previous element ---
+    stack = pop(stack);  // removes 20
+    assert(top(stack) == a);
+    assert(*(int*)top(stack) == 10);
+
+    // --- Test 4: pop() on single element returns NULL ---
+    stack = pop(stack);  // removes 10
+    assert(stack == NULL);
+
+    // --- Test 5: pop() on empty stack returns NULL ---
+    stack = pop(stack);
+    assert(stack == NULL);
+
+    // --- Test 6: clearStack() empties a multi-element stack ---
+    int *c = make_int(1);
+    int *d = make_int(2);
+    int *e = make_int(3);
+    stack = push(stack, c);
+    stack = push(stack, d);
+    stack = push(stack, e);
+
+    clearStack(stack);
+    // stack pointer still points to old top; we must reset manually
+    stack = NULL;
+
+    // no crash = success
+
+    // free remaining data
+    free(a);
+    free(b);
+    free(c);
+    free(d);
+    free(e);
+
+    printf("All tests passed successfully.\n");
+
+    return 0;
+}