diff --git a/codereview-test b/codereview-test
new file mode 100644
index 0000000..8fb732a
--- /dev/null
+++ b/codereview-test
@@ -0,0 +1,79 @@
+#!/usr/bin/env python3
+"""
+A simple calculator script with various errors for testing code review tools.
+"""
+
+import os
+import sys
+import json  # unused import
+
+def calculate_average(numbers):
+    # Missing input validation
+    total = 0
+    for num in numbers:
+        total += num
+    # Division by zero potential
+    return total / len(numbers)
+
+def process_data(data):
+    # Undefined variable error
+    result = []
+    for item in data:
+        if item > threshold:  # threshold is not defined
+            result.append(item * 2)
+    return result
+
+class Calculator:
+    def __init__(self):
+        self.history = []
+    
+    def add(self, a, b):
+        # Missing type hints and validation
+        result = a + b
+        self.history.append(result)
+        return result
+    
+    def divide(self, a, b):
+        # No zero division check
+        return a / b
+    
+    def get_history(self):
+        # Returning mutable reference
+        return self.history
+
+def main():
+    # Syntax error - missing closing bracket
+    numbers = [1, 2, 3, 4, 5
+    
+    # Logic error - wrong function name
+    avg = calculate_mean(numbers)  # function is called calculate_average
+    print(f"Average: {avg}")
+    
+    # Unused variable
+    unused_var = "this is never used"
+    
+    # Inefficient loop
+    large_list = list(range(10000))
+    squared = []
+    for i in range(len(large_list)):  # should use enumerate or direct iteration
+        squared.append(large_list[i] ** 2)
+    
+    # String concatenation in loop (inefficient)
+    message = ""
+    for i in range(100):
+        message += f"Item {i} "
+    
+    # Security issue - using eval
+    user_input = "2 + 2"
+    result = eval(user_input)
+    
+    # Missing exception handling
+    with open("nonexistent_file.txt", "r") as f:
+        content = f.read()
+    
+    calc = Calculator()
+    # Potential error - passing string to add method
+    calc.add("5", 3)
+
+if __name__ == "__main__":
+    main()