5.6. Summary of Techniques

Boundary Value Analysis

• Best For: Edge conditions and numeric ranges
• Example Scenario: Age limits, input ranges

Boundary Value Analysis (BVA) focuses on testing the extreme boundaries of input ranges. This is because a significant number of errors occur at the edges rather than in the middle of the input range. For example, if a field accepts ages from 18 to 60, BVA would also test the values at 17 (just below the minimum), 18 (minimum), 59 (just below the maximum), and 60 (maximum), alongside 61 (just above the maximum). Such testing helps ensure that these boundary conditions are properly handled by the software.

Think of BVA like testing the height requirement at an amusement park ride. If the ride requires you to be between 42 and 60 inches tall, you'd want to measure just below 42 inches (41), right at 42 (the minimum), just below 60 inches (59), and right at 60 (the maximum) to make sure everyone within those bounds is handled correctly.

Equivalence Partitioning

• Best For: Grouping valid/invalid inputs
• Example Scenario: Form fields, password strength

Equivalence Partitioning (EP) is a technique used to minimize the number of test cases by grouping similar inputs into equivalence classes. Each class is treated as if it’s the same as any other member of that class. For instance, if a form validates age between 18 and 60, you perform tests only with one valid age (e.g., 25) and one invalid age from each class (e.g., 10 for below range and 70 for above range). This way, you efficiently check if the system correctly handles valid and invalid inputs without testing every single value.

Consider testing a customer service response system. Instead of sending individual emails to test how long it takes to respond for every client inquiry, you could group inquiries into simple classes like 'general questions,' 'billing issues,' and 'technical support.' By sending one example from each group, you can swiftly evaluate the system without needing to test every single possible inquiry.

Decision Table Testing

• Best For: Complex rule-based logic
• Example Scenario: Loan approval, discount rules

Decision Table Testing involves creating a table that maps different combinations of inputs to expected outputs. This is particularly useful for scenarios involving multiple conditions or rules. For example, in a loan approval process, combinations of income and credit score can lead to different outcomes: approve, review, or reject. By laying these combinations out in a table, it becomes easier to visualize and test all possible scenarios to ensure that the system responds correctly in each case.

Imagine you are at a restaurant that has various conditions for discounts based on the total bill and time of day. By using a decision table, you could outline different scenarios like 'total 50 during lunch,' 'total 80 during dinner,' etc. Each combination might trigger a different discount. By organizing these combinations in a table, you can simplify the way you check if the proper discounts are applied.

State Transition Testing

• Best For: Systems with different states
• Example Scenario: ATM, login/logout, cart flow

State Transition Testing is a method used to analyze the behavior of systems based on changes in state caused by user actions or inputs. This is particularly relevant for systems that have distinct states and transitions between them, such as logging in and out of an account. For example, if a user is logged into an ATM system, various scenarios can occur based on their actions, like inserting a card, entering a PIN, or withdrawing cash. Testing the transitions ensures that all valid and erroneous paths through the system are handled appropriately.

Think of State Transition Testing like a video game where your character can switch between different modes, such as 'running,' 'jumping,' and 'crouching.' Each mode can trigger different actions and outcomes. If you tested only one mode without checking how transitions between running and jumping affect gameplay, you might miss crucial bugs that only appear at the boundaries of those modes.

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