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<String> validatePassword(String password) {
        List<String> 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<String> result = 
            PasswordValidator.validatePassword(
            "StrongPass1");
        assertEquals("Password is valid.", result.get(0));
    }

    @Test
    public void testTooShortPassword() {
        List<String> result = PasswordValidator.validatePassword(
            "Short1");
        assertTrue(result.contains(
            "Password must be at least 8 characters long."));
    }

    @Test
    public void testNoUppercase() {
        List<String> result = PasswordValidator.validatePassword(
            "nouppercase1");
        assertTrue(
            result.contains(
                "Password must contain at least one uppercase letter."));
    }

    @Test
    public void testNoLowercase() {
        List<String> result = PasswordValidator.validatePassword(
            "NOLOWERCASE1");
        assertTrue(result.contains(
            "Password must contain at least one lowercase letter."));
    }

    @Test
    public void testNoNumber() {
        List<String> 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. Tags Testing Level [x]Beginner AI Generation AI can generate regular expressions but often fails to provide helpful error messages. Without proper instructions, AI-generated validators may fail to guide users through fixing their inputs. AI Detection AI can detect basic regular expression patterns and missing feedback with clear prompting. it might not automatically create detailed test cases or descriptions unless asked specifically. Try Them! Remember: AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini Conclusion A regular expression without clear feedback is user-unfriendly and prone to errors. It would help if you described why they failed and wrote thorough tests to ensure your regex works as expected. Relations https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-ix-7rr33ol?embedable=true Code Smell 185 - Evil Regular Expressions https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xx-we-have-reached-100?embedable=true Disclaimer Code Smells are my opinion. Credits Photo by rc.xyz NFT gallery on Unsplash Feedback is the breakfast of champions. Ken Blanchard https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true This article is part of the CodeSmell Series. https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-i-xqz3evd?embedable=true Regex Without Tests is Asking for Trouble - Don't be lazy. It is free with AI! 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. 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 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 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 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,}$");
        // This is a cryptic Regular Expression
    }
} public class PasswordValidator {
    public static boolean isValidPassword(String password) {
        return password.matches(
            "^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)[a-zA-Z\\d]{8,}$");
        // This is a cryptic Regular Expression
    }
} Right import java.util.ArrayList;
import java.util.List;

public class PasswordValidator {
    public static List<String> validatePassword(String password) {
        List<String> 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<String> result = 
            PasswordValidator.validatePassword(
            "StrongPass1");
        assertEquals("Password is valid.", result.get(0));
    }

    @Test
    public void testTooShortPassword() {
        List<String> result = PasswordValidator.validatePassword(
            "Short1");
        assertTrue(result.contains(
            "Password must be at least 8 characters long."));
    }

    @Test
    public void testNoUppercase() {
        List<String> result = PasswordValidator.validatePassword(
            "nouppercase1");
        assertTrue(
            result.contains(
                "Password must contain at least one uppercase letter."));
    }

    @Test
    public void testNoLowercase() {
        List<String> result = PasswordValidator.validatePassword(
            "NOLOWERCASE1");
        assertTrue(result.contains(
            "Password must contain at least one lowercase letter."));
    }

    @Test
    public void testNoNumber() {
        List<String> result = PasswordValidator.validatePassword(
            "NoNumberPass");
        assertTrue(result.contains(
            "Password must contain at least one digit."));
    }
} import java.util.ArrayList;
import java.util.List;

public class PasswordValidator {
    public static List<String> validatePassword(String password) {
        List<String> 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<String> result = 
            PasswordValidator.validatePassword(
            "StrongPass1");
        assertEquals("Password is valid.", result.get(0));
    }

    @Test
    public void testTooShortPassword() {
        List<String> result = PasswordValidator.validatePassword(
            "Short1");
        assertTrue(result.contains(
            "Password must be at least 8 characters long."));
    }

    @Test
    public void testNoUppercase() {
        List<String> result = PasswordValidator.validatePassword(
            "nouppercase1");
        assertTrue(
            result.contains(
                "Password must contain at least one uppercase letter."));
    }

    @Test
    public void testNoLowercase() {
        List<String> result = PasswordValidator.validatePassword(
            "NOLOWERCASE1");
        assertTrue(result.contains(
            "Password must contain at least one lowercase letter."));
    }

    @Test
    public void testNoNumber() {
        List<String> result = PasswordValidator.validatePassword(
            "NoNumberPass");
        assertTrue(result.contains(
            "Password must contain at least one digit."));
    }
} Detection [x]Automatic [x] Automatic [x] 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. Tags Testing Testing Level [x]Beginner [x] Beginner [x] AI Generation AI can generate regular expressions but often fails to provide helpful error messages. Without proper instructions, AI-generated validators may fail to guide users through fixing their inputs. AI Detection AI can detect basic regular expression patterns and missing feedback with clear prompting. it might not automatically create detailed test cases or descriptions unless asked specifically. Try Them! Remember: AI Assistants make lots of mistakes Remember: AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini Without Proper Instructions

With Specific Instructions ChatGPT

ChatGPT Claude

Claude Perplexity

Perplexity Copilot

Copilot Gemini

Gemini Without Proper Instructions With Specific Instructions Without Proper Instructions Without Proper Instructions With Specific Instructions With Specific Instructions ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT Claude Claude Claude Claude Claude Claude Claude Claude Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Copilot Copilot Copilot Copilot Copilot Copilot Copilot Copilot Gemini Gemini Gemini Gemini Gemini Gemini Gemini Gemini Conclusion A regular expression without clear feedback is user-unfriendly and prone to errors. It would help if you described why they failed and wrote thorough tests to ensure your regex works as expected. Relations https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-ix-7rr33ol?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-ix-7rr33ol?embedable=true Code Smell 185 - Evil Regular Expressions Code Smell 185 - Evil Regular Expressions https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xx-we-have-reached-100?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xx-we-have-reached-100?embedable=true Disclaimer Code Smells are my opinion . opinion Credits Photo by rc.xyz NFT gallery on Unsplash rc.xyz NFT gallery Unsplash Feedback is the breakfast of champions. Feedback is the breakfast of champions. Ken Blanchard Ken Blanchard https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true This article is part of the CodeSmell Series. https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-i-xqz3evd?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-i-xqz3evd?embedable=true

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