
import unittest
import user_code
import ast
import re   
import unittest
import importlib
import io
from contextlib import redirect_stdout

class TestTask(unittest.TestCase):
    def test_add(self):
        import user_code
        importlib.reload(user_code)
        result = user_code.safe_calculator("add", 7, 5)
        _dynamic_test(
            self,
            result == 12,
            "Addition returns correct sum",
            f"Expected 12, got {result}",
        )

    def test_subtract(self):
        import user_code
        importlib.reload(user_code)
        result = user_code.safe_calculator("subtract", 10, 3)
        _dynamic_test(
            self,
            result == 7,
            "Subtraction returns correct difference",
            f"Expected 7, got {result}",
        )

    def test_multiply(self):
        import user_code
        importlib.reload(user_code)
        result = user_code.safe_calculator("multiply", 4, 6)
        _dynamic_test(
            self,
            result == 24,
            "Multiplication returns correct product",
            f"Expected 24, got {result}",
        )

    def test_divide(self):
        import user_code
        importlib.reload(user_code)
        result = user_code.safe_calculator("divide", 20, 5)
        _dynamic_test(
            self,
            result == 4,
            "Division returns correct quotient",
            f"Expected 4, got {result}",
        )

    def test_divide_by_zero(self):
        import user_code
        importlib.reload(user_code)
        result = user_code.safe_calculator("divide", 20, 0)
        _dynamic_test(
            self,
            result is None,
            "Division by zero returns None",
            f"Expected None for division by zero, got {result}",
        )

    def test_unsupported_operation(self):
        import user_code
        importlib.reload(user_code)
        result = user_code.safe_calculator("power", 2, 3)
        _dynamic_test(
            self,
            result is None,
            "Unsupported operation returns None",
            f"Expected None for unsupported operation, got {result}",
        )

def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)

def normalize_text(text):
    text = text.lower()
    text = re.sub(r"\\s{2,}", " ", text)
    text = re.sub(r"\\s*([,:?])\\s*", r"\\1 ", text)
    return text.strip()

def change_var(code: str, var_name: str, value: str) -> str:
    tree = ast.parse(code)
    lines = code.splitlines()
    changed = False
    # Collect all assignment nodes to modify
    assign_nodes = [
        (i, node)
        for i, node in enumerate(tree.body)
        if isinstance(node, ast.Assign)
        and any(isinstance(target, ast.Name) and target.id == var_name for target in node.targets)
    ]

    # If nothing to change, return unmodified code
    if not assign_nodes:
        return code

    # Perform replacements for all matching assignments (from last to first to not break line offsets)
    for i, node in reversed(assign_nodes):
        start_line = node.lineno - 1
        line = lines[start_line]
        indent = ' ' * (len(line) - len(line.lstrip()))
        lines[start_line] = f"{indent}{var_name} = {value}"
        next_line = len(lines)
        for next_node in tree.body[i+1:]:
            if hasattr(next_node, 'lineno'):
                next_line = next_node.lineno - 1
                break
        if next_line > start_line + 1:
            lines[start_line+1:next_line] = []
        changed = True

    return '\\n'.join(lines) if changed else code

if __name__ == "__main__":
    unittest.main()


test_main.py

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Explore the most common security pitfalls in Python, how vulnerabilities arise, and the foundational principles for writing secure code.

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Challenge: Preventing Code Injection

Solution

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Challenge: Preventing Code Injection

Solution