ISTQB CHAPTER 4: Test Design Techniques – Black-box test design

Tram Ho

1. What is the Black-box testing?

  • Black-box testing is the performance of testing the functionality of an application without regard to its internal structure, design or coding.
  • The main purpose is to confirm whether the software works in response to the customer’s specification or expectations.
  • Usually performed by testers.
  • Applicable for stages:
    • Unit test
    • Integration test
    • System test
    • Acceptance test
    • Regression testing.

2. Black Box test design

2.1 Equivalence partitioning (EP) – Equivalent Partitioning (EP)

  • The technique of partitioning inputs and outputs into regions of similar behavior to be treated in the same way
  • One value in the active equivalence region -> means that the remaining values ​​in the region will work as well
  • When design tests will include all valid and invalid partitions

Example: At a vegetable shopping site. This page only allows you to submit orders when you purchase a minimum of 0.5 kg and a maximum of 25 kg.

From there we can divide into 3 equivalent partitions as follows:

Zone 1: x <0.5 kg

Zone 2: 0.5 kg <= x <= 25 kg

Area 3: x> 25 kg

Since the system only accepts the value “0.5 gram <= x <= 25 kg”, this is called a valid partition. The remaining 2 partitions are invalid.

2.2 Boundary value analysis (BVA) – Marginal value analysis (BVA)

  • Boundary: The value at the edge of each equivalent partition
  • This value is often not as accurate as the values ​​inside the equivalence range, so it is the place where errors are most common
  • Two-point boundary: the maximum and minimum value of the equivalent partition
  • Three boundary values: values ​​before, at and immediately above the boundary value
  • Design tests should include all valid and invalid boundary values

As in the above example, we have 2 marginal values ​​0.5 and 25

When referring to an equivalent partition, it will be given priority to pick the middle values ​​to test (eg 0.2, 15, 35) while with “Two-point boundary” it will be the boundary values: 04, 0, 5, 25, 25.1

Similarly three boundary values: 0.4, 0.5, 0.6, 24.9, 25, 25.1

2.3 Decision tables – decision table

  • Discover combinations of inputs, outputs, actions: Determines input values, possible actions, and possible output. From there create a table to keep track of possible cases.
  • The values ​​for conditions and actions are usually displayed as Boolean (True or False) values.

A simple example for the login form


Combining the true / false conditions of the input will give different results. Corresponding to the possible circumstances.

From there, you can pick the appropriate test case to ensure coverage.

2.4 State transition testing – Test transitions

  • Using the state transition graph to see possible software states, passing different Input values ​​produces different state results. From there, have an overview and understand the handling of the system

For example: ATM station allows access to the account when the user enters the wrong pin number not more than 3 times, if more than 3 times, the card will be swallowed.

From the request above we have a state diagram table as shown below

To cover 100% state transition coverage, make sure all state is passed => like this example we have 2 tcs as below:

TC1: Start ==> Access to account

TC2: Start ==> Eat Card

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Source : Viblo