Decision Table Testing: A Complete Guide

Testing software, especially complex systems, can be a daunting task. But what if there was a way to systematically test every possible input combination without getting overwhelmed? That’s where Decision Table Testing comes in!

As a black-box testing technique, Decision Table Testing helps testers map various combinations of inputs (conditions) to their corresponding outputs (actions), ensuring comprehensive test coverage without redundancy. Let’s dive into how this technique can make your testing process smarter and more efficient.

What is Decision Table Testing?

Decision Table Testing is a black-box testing method that represents different combinations of inputs and their corresponding outcomes in a structured tabular format. It consists of three primary elements:

1. Conditions: The input variables that impact the system’s behavior.
2. Actions: The outcomes or system responses based on combinations of conditions.
3. Rules: Specific combinations of conditions and their corresponding actions.

This method allows testers to cover multiple scenarios systematically by defining and organizing the rules that guide the system’s behavior. Each rule represents a unique combination of inputs that yield a specific output, simplifying the testing process.

Decision Table Layout

A decision table consists of rows for conditions and actions, with each column representing a specific rule—a unique combination of conditions and the corresponding action(s).

Let’s look at a simple loan approval system to see how Decision Table Testing works in practice. The system evaluates a loan application based on two conditions:

1. Credit Score (High, Medium, Low)
2. Income (High, Low)

Based on these factors, the system decides whether to approve the loan and, if approved, the applicable interest rate. For example:

• Rule 1: High Credit Score, High Income – Loan is approved with a low interest rate.
• Rule 4: Medium Credit Score, Low Income – Loan is not approved, so interest rate is not applicable (N/A).

Each column in the decision table represents a specific test case. In this example, you have six test cases that comprehensively cover all possible scenarios the loan approval system may face.

How Decision Table Testing Works

Here’s how you can create your own decision table in four simple steps:

1. Identify the conditions and actions your system uses.
2. Create all possible combinations of these conditions.
3. Define the corresponding action(s) for each combination.
4. Populate the decision table and convert each rule (column) into a test case.

By following these steps, testers can create a decision table that simplifies the system’s decision-making process into an organized, testable format.

Benefits of Decision Table Testing

Why should you choose Decision Table Testing? 

For starters, it ensures you don’t miss any potential input combinations. Plus, it simplifies your testing process by organizing all the conditions and outcomes into one easily digestible format.

This method also improves communication between teams. When you consolidate business requirements into a single table, everyone (including developers, testers, and business analysts) can all stay on the same page. And, because the decision table format is reusable, you can easily modify it for different testing scenarios.

Best Practices for Decision Table Testing

To get the most out of Decision Table Testing, here are some best practices:

1. Start Simple: Begin with the most straightforward conditions and actions, then gradually add complexity as needed.
2. Use Equivalence Partitioning: If a condition involves a range of values (e.g., age 18-60), use equivalence partitioning to reduce the number of test cases. Test at both the low and high ends of the range to cover all scenarios efficiently.
3. Test Boundaries: Always test boundary conditions to ensure the system behaves correctly at the edges of acceptable input ranges.

When to Use Decision Table Testing

Decision Table Testing is ideal for systems with complex business rules that rely on multiple input combinations. It’s particularly useful for systems where combinations of conditions need to be tested to ensure the correct action is taken every time.

Common Use Cases for Decision Table Testing:

• Loan approval systems
• Insurance claim approvals
• E-commerce product recommendations
• User access control based on role and permissions
• Configurable settings in software applications

Wherever multiple conditions and actions must be evaluated, Decision Table Testing offers a practical, organized way to cover all scenarios.

Conclusion

Decision Table Testing is a powerful tool for simplifying your test cases while ensuring nothing is missed. By mapping conditions to actions in a decision table, testers can ensure comprehensive test coverage, identify potential gaps, and streamline their testing process.