Code Smell 276 - Untested Regular Expressions

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Code Smell 276 - Untested Regular Expressions

Tags: google testing

Author: DATE POSTED:October 27, 2024

Feed: Hacker Noon - Medium

View: Original article

Regex Without Tests is Asking for Trouble - Don't be lazy. It is free with AI!

TL;DR: Use clear and concise regular expressions, and test them thoroughly.

Problems

Readability
No test cases
Missed edge cases
Debugging challenges
Unclear failures
Hidden defects

Solutions

Ask your favorite AI to write test cases
Break down complex regular expressions into smaller, more readable parts.
Check edge cases
Validate outputs
Refactor regex once you created the tests
Improve the Error Messages

Context

Regular expressions are powerful but tricky.

\ If you write a regex without tests, you're asking for unexpected errors.

\ If you write a cryptic regex and skip automated testing, you could miss important cases, causing security issues or user frustration.

Sample Code Wrong public class PasswordValidator { public static boolean isValidPassword(String password) { return password.matches( "^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)[a-zA-Z\\d]{8,}$"); // This is a cryptic Regular Expression } } Right import java.util.ArrayList; import java.util.List; public class PasswordValidator { public static List validatePassword(String password) { List errors = new ArrayList<>(); if (password.length() < 8) { errors.add( "Password must be at least 8 characters long."); } if (!password.matches(".*[A-Z].*")) { errors.add( "Password must contain at least one uppercase letter."); } if (!password.matches(".*[a-z].*")) { errors.add( "Password must contain at least one lowercase letter."); } if (!password.matches(".*\\d.*")) { errors.add( "Password must contain at least one digit."); } if (errors.isEmpty()) { errors.add( "Password is valid."); } return errors; // You no longer need a Regular Expression!! } } import static org.junit.Assert.*; import org.junit.Test; public class PasswordValidatorTest { // Now you have a lot of tests // You can use a Regular Expression, // a String Validator // an External Library // Whatever you want as long as it passes the tests! @Test public void testValidPassword() { List result = PasswordValidator.validatePassword( "StrongPass1"); assertEquals("Password is valid.", result.get(0)); } @Test public void testTooShortPassword() { List result = PasswordValidator.validatePassword( "Short1"); assertTrue(result.contains( "Password must be at least 8 characters long.")); } @Test public void testNoUppercase() { List result = PasswordValidator.validatePassword( "nouppercase1"); assertTrue( result.contains( "Password must contain at least one uppercase letter.")); } @Test public void testNoLowercase() { List result = PasswordValidator.validatePassword( "NOLOWERCASE1"); assertTrue(result.contains( "Password must contain at least one lowercase letter.")); } @Test public void testNoNumber() { List result = PasswordValidator.validatePassword( "NoNumberPass"); assertTrue(result.contains( "Password must contain at least one digit.")); } } Detection

[x] Automatic

You can detect when your regex is uncovered by changing it to fail and running all your tests.

\ If your validation returns "false" without user-friendly explanations, it's a clear sign you need to refactor it and improve the feedback.