Functional Testing in Software Development: What It Is and Why It Matters

In the world of software development, ensuring that an application behaves as expected is crucial. One of the most common ways to verify this is through functional testing. This method focuses on testing the software against the defined specifications and requirements. It answers the fundamental question: Does this software do what it's supposed to do?

Functional testing plays a pivotal role in validating that each feature of the software functions in accordance with the requirement documents. It is often conducted using black-box testing techniques, meaning the tester doesn't need to know the internal workings of the code. Instead, the focus remains on the input and expected output.

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Why Functional Testing Is Important

• Ensures Business Requirements Are Met: Functional testing ensures that the software delivers what the stakeholders expect.

• Identifies Gaps Early: Finding bugs early in the development cycle saves time, money, and resources.

• Improves User Satisfaction: When applications work as intended, users are more likely to trust and continue using them.

• Regulatory and Compliance Standards: Many industries require rigorous testing for safety and compliance.

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Core Areas of Functional Testing

Functional testing usually revolves around several key areas:

1. User Interface Testing: Verifies that UI elements function as expected.

2. API Testing: Ensures APIs return correct responses for different requests.

3. Database Testing: Confirms data is correctly stored and retrieved.

4. Security Testing: Checks for vulnerabilities and proper user access.

5. Boundary Testing: Tests the system's response to boundary input conditions.

6. Error Handling Testing: Verifies appropriate error messages and behaviors.

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Types of Functional Testing

There are multiple types of functional tests. These include:

1. Unit Testing

• Typically performed by developers.

• Focuses on individual units or components of the software.

2. Smoke Testing

• A preliminary test to check the basic functionality of the application.

• Often used after a new build is released.

3. Sanity Testing

• Ensures that specific functions work after changes or bug fixes.

4. Regression Testing

• Ensures new code changes do not adversely affect the existing functionality.

5. Integration Testing

• Checks how different components or systems work together.

6. User Acceptance Testing (UAT)

• Done by the client or end-user.

• Ensures the software meets the business needs.

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Manual vs Automated Functional Testing

Manual Testing

Pros:

• More flexibility

• Suitable for exploratory testing

Cons:

• Time-consuming

• Prone to human error

Automated Testing

Pros:

• Fast and efficient for repetitive tasks

• Excellent for regression testing

Cons:

• Requires initial setup time

• Not ideal for all types of tests

Popular tools include Selenium, QTP, TestComplete, and JUnit.

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Steps Involved in Functional Testing

1. Understand Requirements: Analyze requirement specifications.

2. Test Planning: Develop a test strategy and plan.

3. Test Case Design: Create detailed test cases and scenarios.

4. Test Execution: Run tests manually or via automation.

5. Defect Reporting: Log any bugs found.

6. Retesting: Validate fixes.

7. Final Report: Summarize outcomes.

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Real-World Example

Imagine a simple login page for a banking app. Functional testing would cover:

• Entering valid and invalid credentials

• Resetting passwords

• Checking login success and failure messages

• Ensuring redirection after login

These tests make sure users can safely and reliably access their accounts.

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Challenges in Functional Testing

• Changing Requirements: Agile methodologies mean constant change.

• Incomplete Specifications: Lack of clarity in documents can lead to missed test cases.

• Environment Issues: Test environments may not always match production.

• Time Constraints: Deadlines can push for shortcuts.

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Best Practices for Effective Functional Testing

• Start Early: Integrate testing from the requirement phase.

• Use Realistic Test Data: Mimic actual user behavior.

• Automate Wisely: Balance manual and automated testing.

• Keep Tests Reusable and Modular: Makes maintenance easier.

• Review Test Cases: Peer reviews can catch missed scenarios.

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Tools for Functional Testing

Some widely used tools include:

• Selenium (Web testing)

• Postman (API testing)

• JMeter (Load testing)

• JUnit/NUnit (Unit testing)

• Cypress (Modern frontend testing)

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Functional Testing in Agile and DevOps

Functional testing must adapt to continuous integration/continuous deployment (CI/CD) pipelines. Agile teams perform functional testing in short sprints. Tools like Jenkins integrate testing into automated build processes, ensuring early bug detection.

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Final Thoughts

Functional testing is a cornerstone of quality assurance in software development. By ensuring that software behaves as expected, teams can deliver products that are robust, user-friendly, and compliant with business goals.

How to Write Modular and Reusable Code: A Guide for Developers

Writing modular and reusable code is a skill every developer should master. It makes your projects easier to manage, reduces bugs, and saves time when you need to update or scale your software. Whether you’re building a small app or a large-scale system, modular code helps you work smarter, not harder. With the increasing complexity of software projects and the rise of collaborative development, writing modular and reusable code is more important than ever. In this article, we’ll explain what modular and reusable code means, why it matters, and share practical tips to help you write better code. Written for developers with some tech experience, this guide will show you how to create code that’s clean, efficient, and easy to reuse. Let’s dive in and level up your coding skills!

What Is Modular and Reusable Code?

Modular code refers to breaking your program into smaller, independent pieces—or modules—that each handle a specific task. Think of it like building with LEGO bricks: each brick (module) has its own purpose, but you can combine them to create something bigger. Reusable code, on the other hand, means writing those modules in a way that you can use them in other projects or parts of your program without rewriting them. Together, modular and reusable code makes your work more organized, easier to debug, and adaptable to future changes.

For example, imagine you’re building a website with a login feature. Instead of writing all the login logic in one big file, you create a separate module for user authentication. This module handles tasks like verifying passwords and generating tokens. Later, if you build another app that needs a login feature, you can reuse that same module without starting from scratch. That’s the power of modular and reusable code—it saves time and keeps your projects consistent.

Modular and reusable code is a core principle in software development, often used in languages like JavaScript, Python, and Java. It’s also a key part of modern frameworks like React or Django, which encourage breaking code into components or modules for better organization.

Why Write Modular and Reusable Code?

Writing modular and reusable code offers several benefits that can improve your development process. Here’s why it’s worth the effort:

• Easier Maintenance: Smaller modules are simpler to understand and fix. If a bug appears in your login module, you can debug just that piece without touching the rest of your code. This makes maintenance faster and less stressful.
• Better Collaboration: In a team, modular code lets multiple developers work on different parts at the same time. For example, one developer can focus on the payment module while another works on the user profile module, reducing conflicts in shared codebases.
• Scalability: Modular code makes it easier to add new features. If you want to add two-factor authentication to your login system, you can update just the login module without rewriting the entire app.
• Time Savings with Reusability: Reusable code lets you use the same logic across projects. For instance, a utility module for formatting dates can be reused in a blog app, an e-commerce site, or a dashboard, saving you from writing the same code repeatedly.
• Fewer Bugs: Smaller, focused modules are easier to test and less likely to break. If your payment module works perfectly in one project, reusing it in another project means you’re less likely to introduce new bugs.
• Consistency: Reusable code ensures consistency across your projects. If you have a standard module for handling errors, all your apps will handle errors the same way, making them more predictable for users and developers.

In today’s fast-paced tech world, where projects often involve large teams and tight deadlines, modular and reusable code is a must for staying efficient and delivering high-quality software.

How to Write Modular and Reusable Code: Practical Tips

Here are some practical tips to help you write modular and reusable code in your projects. These tips work across most programming languages and frameworks, so you can apply them to your work right away.

• Break Code into Small, Focused Modules: Start by dividing your code into small, single-purpose modules. Each module should do one thing and do it well—a principle called the Single Responsibility Principle (SRP). For example, in a Python app, you might have a database.py module for database connections, a user_auth.py module for authentication, and a utils.py module for helper functions like date formatting. Keeping modules focused makes them easier to understand and reuse.
• Use Functions and Classes Wisely: Functions and classes are great for creating modular code. Write functions that handle specific tasks—like a calculateTax(amount) function in JavaScript—and classes that group related functionality. For example, in a Java app, you might create a User class with methods like login(), logout(), and updateProfile(). This keeps related code together and makes it reusable in other parts of your program.
• Follow Naming Conventions: Use clear, descriptive names for your modules, functions, and variables so their purpose is obvious. For instance, a function named sendEmail(to, subject, body) is easier to understand than se(t, s, b). Good naming makes your code more reusable because other developers (or your future self) can quickly figure out what each module does without digging through the code.
• Avoid Hardcoding Values: Hardcoding values—like API keys, file paths, or specific numbers—makes your code less reusable. Instead, use configuration files or environment variables. For example, in a Node.js app, store your API key in a .env file using a library like dotenv, then access it with process.env.API_KEY. This way, you can reuse the same module in different projects by just changing the config file.
• Write Generic, Flexible Code: Make your modules as generic as possible so they can work in different contexts. For example, instead of writing a function that only formats dates for a blog, create a formatDate(date, format) function that lets you specify the output format. This makes the function reusable for a calendar app, an invoice system, or any project needing date formatting.
• Document Your Code: Good documentation is key for reusable code. Add comments or docstrings to explain what each module does, its inputs, and its outputs. For example, in Python, you might write a docstring like this for a function:
  
  

  def calculate_discount(price, percentage): """ Calculate the discount amount for a given price and percentage. Args: price (float): The original price percentage (float): The discount percentage (0-100) Returns: float: The discount amount """ return price * (percentage / 100)
  Clear documentation makes it easier for others to reuse your code without guessing how it works.
• Use Modules and Packages: Most languages support modules or packages to organize code. In JavaScript, use import and export to create modules—like exporting a sendNotification function from a notifications.js file. In Python, organize related modules into a package, like a utils package with submodules for dates, strings, and emails. This structure makes your code modular and easy to import into other projects.
• Test Your Code Thoroughly: Reusable code needs to be reliable, so write unit tests to ensure it works as expected. For example, in a JavaScript project, use a testing framework like Jest to test a formatCurrency(amount) function, checking that it handles different inputs correctly. Tested code gives you confidence to reuse it in new projects without worrying about hidden bugs.
• Avoid Tight Coupling: Tight coupling happens when modules depend too heavily on each other, making them hard to reuse. Aim for loose coupling by using interfaces or dependency injection. For example, in a Java app, instead of a PaymentService class directly creating a StripeClient, pass the client as a dependency: PaymentService(StripeClient client). This way, you can swap StripeClient for another payment client without changing the PaymentService code, making it more reusable.

A Real-World Example of Modular and Reusable Code

Let’s look at an example to see these tips in action. Imagine you’re building a Node.js app for an online store. You need a module to handle email notifications for order confirmations, password resets, and promotions. Instead of writing separate email logic for each feature, you create a reusable email.js module:

// email.js const nodemailer = require('nodemailer'); require('dotenv').config(); const transporter = nodemailer.createTransport({ service: 'gmail', auth: { user: process.env.EMAIL_USER, pass: process.env.EMAIL_PASS, }, }); async function sendEmail(to, subject, body) { const mailOptions = { from: process.env.EMAIL_USER, to, subject, text: body, }; await transporter.sendMail(mailOptions); console.log(`Email sent to ${to}`); } module.exports = { sendEmail };

Now, in your app, you can reuse this module anywhere you need to send an email:

// order.js const { sendEmail } = require('./email'); async function confirmOrder(userEmail, orderId) { await sendEmail(userEmail, 'Order Confirmation', `Your order ${orderId} has been placed!`); } // password.js const { sendEmail } = require('./email'); async function sendPasswordReset(userEmail, resetLink) { await sendEmail(userEmail, 'Password Reset', `Click here to reset your password: ${resetLink}`); }

This module is modular (it handles one task: sending emails), reusable (you can use it for any email need), and flexible (it works with different subjects and bodies). It also avoids hardcoding by using environment variables for the email credentials, making it easy to reuse in other projects.

Common Mistakes to Avoid When Writing Modular Code

While writing modular and reusable code, watch out for these common mistakes:

• Overcomplicating Modules: Don’t make modules too complex by trying to handle too many tasks. A user.js module shouldn’t handle authentication, payments, and logging—split those into separate modules.
• Ignoring Dependencies: If your module relies on external libraries, make sure they’re widely supported and maintained. A module that depends on an outdated library might not be reusable in future projects.
• Skipping Tests: Untested code can break when reused in a new context. Always write tests to ensure your modules work reliably.
• Poor Documentation: Without clear documentation, other developers won’t know how to use your code. Always include comments or docstrings to explain your modules.

Final Thoughts on Writing Modular and Reusable Code

Writing modular and reusable code is a skill that will make you a better developer and save you time in the long run. By breaking your code into small, focused modules, using clear naming, avoiding hardcoding, and documenting your work, you can create code that’s easy to maintain, reuse, and share with others. Whether you’re working on a solo project or with a team, these practices will help you build cleaner, more efficient software. So, the next time you start coding, think modular—your future self will thank you!

Resources for Further Learning

Want to learn more about writing modular and reusable code? Check out these helpful resources:

Books on Amazon:

Clean Code by Robert C. Martin (Buy book - Affiliate link) – A classic book on writing clean, modular code with practical examples.

Refactoring: Improving the Design of Existing Code by Martin Fowler (Buy book - Affiliate link) – Tips on making code more modular and reusable through refactoring.

Navigating the Labyrinth: A Comprehensive Guide to Different Types of Software Testing for Quality Assurance

In the intricate and demanding world of software development, creating a functional product is only half the battle. Ensuring that the software behaves as expected, is robust under various conditions, meets user needs, and is free of critical defects is equally, if not more, crucial. This is where software testing, a vital and multifaceted discipline within the Software Development Life Cycle (SDLC), takes center stage. For individuals with technical experience—developers, QA engineers, project managers, and even informed stakeholders—understanding the diverse types of testing employed is key to appreciating how software quality is systematically built, verified, and validated.

Software testing isn't a monolithic activity; it's a spectrum of methodologies, each designed to scrutinize different aspects of the software, from the smallest individual code units to the entire integrated system operating in a production-like environment. This exploration will delve into the primary categories and common types of software testing, highlighting their objectives, scope, and their indispensable role in delivering reliable and effective software solutions.

Why So Many Types of Testing? A Multi-Layered Approach to Quality

The sheer variety of testing types stems from the complexity of modern software and the numerous ways it can fail or fall short of expectations. A multi-layered testing strategy is essential because:

1. Different Focus Areas: Some tests look at internal code structure (White Box), while others focus solely on external behavior (Black Box). Some assess functionality, while others evaluate performance, security, or usability.

2. Early Defect Detection: Testing at different stages of the SDLC helps catch defects early, when they are generally cheaper and easier to fix. A bug found during unit testing is far less costly than one discovered by end-users in production.

3. Comprehensive Coverage: No single testing type can cover all possible scenarios or defect types. A combination of approaches provides more comprehensive assurance.

4. Risk Mitigation: Different tests target different types of risks (e.g., functional failures, security vulnerabilities, performance bottlenecks).

5. Meeting Diverse Stakeholder Needs: Different stakeholders have different quality concerns (e.g., users care about usability, business owners about meeting functional requirements, operations about stability).

Categorizing the Testing Landscape: Levels and Approaches

Software testing can be broadly categorized in several ways, often by the level at which testing is performed or the approach taken.

I. Testing Levels (Often Sequential in the SDLC):

These levels typically follow the progression of software development.

1. Unit Testing:

   • Focus: Testing individual, atomic components or modules of the software in isolation (e.g., a single function, method, class, or procedure).

   • Performed By: Primarily developers.

   • Approach: Predominantly White Box Testing, as developers have intimate knowledge of the code they are testing. They write test cases to verify that each unit behaves as expected according to its design.

   • Goal: To ensure each small piece of code works correctly before it's integrated with others. Catches bugs at the earliest possible stage.

   • Tools: xUnit frameworks (e.g., JUnit for Java, NUnit for .NET, PyTest for Python), mocking frameworks.

   • Example: A developer writes a unit test for a function that calculates sales tax to ensure it returns the correct tax amount for various input prices and tax rates.

2. Integration Testing:

   • Focus: Testing the interfaces and interactions between integrated components or modules after unit testing is complete. It verifies that different parts of the system work together correctly.

   • Performed By: Developers and/or dedicated testers.

   • Approach: Can be both White Box (testing API contracts and data flows between modules) and Black Box (testing the combined functionality from an external perspective).

   • Goal: To uncover defects that arise when individual units are combined, such as data communication errors, interface mismatches, or unexpected interactions.

   • Strategies: Big Bang (all at once, less common), Top-Down, Bottom-Up, Sandwich/Hybrid.

   • Example: Testing the interaction between a user registration module and a database module to ensure user data is correctly saved and retrieved.

3. System Testing:

   • Focus: Testing the complete, integrated software system as a whole to verify that it meets all specified requirements (both functional and non-functional).

   • Performed By: Primarily independent QA teams or testers.

   • Approach: Predominantly Black Box Testing, as testers evaluate the system based on requirement specifications, use cases, and user scenarios, without needing to know the internal code structure.

   • Goal: To validate the overall functionality, performance, reliability, security, and usability of the entire application in an environment that closely mimics production.

   • Example: Testing an e-commerce website by simulating a user journey: searching for a product, adding it to the cart, proceeding to checkout, making a payment, and receiving an order confirmation.

4. Acceptance Testing (User Acceptance Testing - UAT):

   • Focus: Validating that the software meets the needs and expectations of the end-users or clients and is fit for purpose in their operational environment.

   • Performed By: End-users, clients, or their representatives. Sometimes product owners in Agile.

   • Approach: Exclusively Black Box Testing. Users test the system based on their real-world scenarios and business processes.

   • Goal: To gain final approval from the stakeholders that the software is acceptable for release. This is often the final testing phase before deployment.

   • Types: Alpha Testing (internal testing by users within the development organization), Beta Testing (external testing by a limited number of real users in their own environment before full release).

   • Example: A client tests a newly developed inventory management system by performing their daily inventory tasks to ensure it functions correctly and efficiently for their business needs.

II. Testing Types (Often Categorized by Objective or Attribute):

These types of testing can be performed at various levels (unit, integration, system, acceptance).

A. Functional Testing Types:
These verify what the system does, ensuring it performs its intended functions.

• Smoke Testing (Build Verification Testing): A quick, preliminary set of tests run on a new software build to ensure its basic critical functionalities are working. If smoke tests fail, the build is often rejected for further, more extensive testing. Its goal is to answer "Is this build stable enough for more testing?"

• Sanity Testing: A very brief set of tests performed after a minor code change or bug fix to ensure the change hasn't broken any core functionality. It's a subset of regression testing.

• Regression Testing: Retesting previously tested functionalities after code changes, bug fixes, or enhancements to ensure that existing features still work correctly and that no new bugs (regressions) have been introduced. This is crucial for maintaining software quality over time.

• Usability Testing: Evaluating how easy and intuitive the software is to use from an end-user's perspective. Involves observing real users performing tasks with the system.

• User Interface (UI) Testing / GUI Testing: Verifying that the graphical user interface elements (buttons, menus, forms, etc.) look correct and function as expected across different devices and screen resolutions.

• API Testing: Testing Application Programming Interfaces (APIs) directly to verify their functionality, reliability, performance, and security, independent of the UI.

• Database Testing: Validating data integrity, accuracy, security, and performance of the database components of an application.

B. Non-Functional Testing Types:
These verify how well the system performs certain quality attributes.

• Performance Testing: Evaluating the responsiveness, stability, and scalability of the software under various load conditions.

  • Load Testing: Simulating expected user load to see how the system performs.

  • Stress Testing: Pushing the system beyond its normal operating limits to see how it behaves and when it breaks.

  • Endurance Testing (Soak Testing): Testing the system under a sustained load for an extended period to check for memory leaks or performance degradation over time.

  • Spike Testing: Testing the system's reaction to sudden, large bursts in load.

  • Volume Testing: Testing with large volumes of data.

• Security Testing: Identifying vulnerabilities, threats, and risks in the software application and ensuring that its data and functionality are protected from malicious attacks and unauthorized access. Includes vulnerability scanning, penetration testing, security audits.

• Compatibility Testing: Verifying that the software works correctly across different hardware platforms, operating systems, browsers, network environments, and device types.

• Reliability Testing: Assessing the software's ability to perform its intended functions without failure for a specified period under stated conditions.

• Scalability Testing: Evaluating the system's ability to handle an increase in load (users, data, transactions) by adding resources (e.g., scaling up servers or adding more instances).

• Maintainability Testing: Assessing how easy it is to maintain, modify, and enhance the software. Often related to code quality, modularity, and documentation.

• Portability Testing: Evaluating the ease with which the software can be transferred from one hardware or software environment to another.

• Installation Testing: Verifying that the software can be installed, uninstalled, and upgraded correctly on various target environments.

III. White Box vs. Black Box Testing (A Fundamental Approach Distinction):

This was covered in a previous discussion but is essential to reiterate:

• Black Box Testing: The tester has no knowledge of the internal code structure or design. Focuses on inputs and outputs, verifying functionality against specifications. (Predominant in System and Acceptance Testing).

• White Box Testing (Clear Box/Glass Box Testing): The tester has full knowledge of the internal code structure, logic, and design. Focuses on testing internal paths, branches, and conditions. (Predominant in Unit Testing, common in Integration Testing).

• Grey Box Testing: A hybrid approach where the tester has partial knowledge of the internal workings, perhaps understanding the architecture or data structures but not the detailed code. Often used in integration or end-to-end testing.

The Agile Context: Continuous Testing

In Agile development methodologies, testing is not a separate phase at the end but an integral, continuous activity throughout each iteration (sprint).

• Test-Driven Development (TDD): Developers write unit tests before writing the actual code.

• Behavior-Driven Development (BDD): Tests are written in a natural language format (e.g., Gherkin) based on user stories, facilitating collaboration between developers, testers, and business stakeholders.

• Continuous Integration/Continuous Testing (CI/CT): Automated tests (unit, integration, API) are run automatically every time new code is committed, providing rapid feedback.

Conclusion: A Symphony of Scrutiny for Software Excellence

The diverse array of software testing types forms a comprehensive quality assurance framework, essential for navigating the complexities of modern software development. From the microscopic examination of individual code units in Unit Testing to the holistic validation of the entire system in System Testing and the crucial end-user validation in Acceptance Testing, each level plays a distinct and vital role. Layered upon these are specific approaches like Functional Testing (ensuring it does what it should) and Non-Functional Testing (ensuring it does it well – performantly, securely, usably).

Understanding this "symphony of scrutiny" allows technical professionals and stakeholders alike to appreciate that software quality isn't an accident; it's the result of a deliberate, systematic, and multi-faceted testing effort. By employing a strategic combination of these testing types, tailored to the specific needs and risks of a project, development teams can confidently identify and rectify defects, validate requirements, and ultimately deliver software that is not only functional but also reliable, robust, and a pleasure for users to interact with. In the quest for software excellence, thorough and diverse testing is the unwavering compass.

Further References & Learning:

Books on Software Testing and Quality Assurance (Available on Amazon and other booksellers):

"Software Testing: A Craftsman's Approach" by Paul C. Jorgensen (Buy book - Affiliate link): A comprehensive and widely respected textbook covering various testing techniques and theories.

"Lessons Learned in Software Testing: A Context-Driven Approach" by Cem Kaner, James Bach, and Bret Pettichord (Buy book - Affiliate link): A classic that offers practical wisdom and insights from experienced testers.

"Foundations of Software Testing ISTQB Certification" by Dorothy Graham, Erik van Veenendaal, Isabel Evans, and Rex Black (Buy book - Affiliate link): A standard guide for those preparing for ISTQB certification, covering fundamental testing concepts and types.

"Agile Testing: A Practical Guide for Testers and Agile Teams" by Lisa Crispin and Janet Gregory (Buy book - Affiliate link) (Buy book - Affiliate link): Focuses on testing practices within Agile methodologies.

"Explore It!: Reduce Risk and Increase Confidence with Exploratory Testing" by Elisabeth Hendrickson (Buy book - Affiliate link): A guide to the powerful technique of exploratory testing.

"The Art of Software Testing (3rd Edition)" by Glenford J. Myers, Corey Sandler, Tom Badgett (Buy book - Affiliate link): Another foundational text in the field.