The Make-Buy Decision or Decision Table - Software Engineering

A decision table is a brief visual representation for specifying which actions to perform depending on given conditions. This article focuses on discussing decision tables in detail.

What is a Decision Table?

A decision table is a good way to settle different combination inputs with their corresponding outputs and is also called a cause-effect table.

1. The reason to call the cause-effect table is a related logical diagramming technique called cause-effect graphing that is used to obtain the decision table. 
2. The information represented in decision tables can also be represented as decision trees or in a programming language using if-then-else and switch-case statements. 

Importance of Decision Table

Decision tables are very helpful in test design techniques.

1. Helps testers to search effects of combinations: It helps testers to search the effects of combinations of different inputs and other software states that must correctly implement business rules.
2. Helps to start complex business rules: It provides a regular way of starting complex business rules, that is helpful for developers as well as for testers.
3. Helps in the development process: It assists in the development process with the developer to do a better job. Testing with all combinations might be impractical.
4. Used in testing: A decision table is basically an outstanding technique used in both testing and requirements management.
5. Helps to prepare requirements: It is a structured exercise to prepare requirements when dealing with complex business rules.
6. Helps to model complicated logic: It is also used to model complicated logic.

Decision Table in Test Designing

Blank Decision Table

CONDITIONS STEP 1 STEP 2 STEP 3 STEP 4

Condition 1

Condition 2

Condition 3

Condition 4

Decision Table: Combinations 

CONDITIONS STEP 1 STEP 2 STEP 3 STEP 4

Condition 1 Y Y N N

Condition 2 Y N Y N

Condition 3 Y N N Y

Condition 4 N Y Y N

Advantages of Decision Table

1. Easy conversion of business flow to test case: Any complex business flow can be easily converted into test scenarios and test cases using this technique.
2. Works iteratively: Decision tables work iteratively which means the table created at the first iteration is used as input tables for the next tables. The iteration is done only if the initial table is not satisfactory.
3. Simple to understand: Simple to understand and everyone can use this method to design the test scenarios & test cases.
4. Provides complete test case coverage: It provides complete coverage of test cases which helps to reduce the rework on writing test scenarios & test cases.
5. Guarantees every combination is considered: These tables guarantee that we consider every possible combination of condition values. This is known as its completeness property.