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What is Black Box Testing? Examples and Tips

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What is Black Box Testing? Examples and Tips

Black box testing is a type of testing that examines the functionality of an application without peering into its structures. This type of test can be implemented virtually to every level of testing: unit, integration, system and acceptance. It is sometimes referred to as specification-based testing.

Black box testing is a powerful testing technique because it works with a system end-to-end. Just like end-users, how a system is coded and expect to receive an appropriate answer to their requests, a tester can simulate user activities and see if the system delivers on its promises. Along the way, a black box test evaluates all relevant subsystems, including UI/UX, database, dependencies, and integrated systems.

INPUT  —- Black Box Testing — Output

Black Box Testing Pros and Cons

Pros:

  1. Testers do not require technical knowledge or IT skills.
  2. Testers do not need to learn implementation details of the system.
  3. Tests can be executed by crowdsourced or outsourced testers.
  4. Low probability of false positives

Cons:

  1. Difficult to Automate
  2. Requires prioritization to test all user paths
  3. Difficult to calculate test coverage
  4. If a test didn’t pass, it can be difficult to understand the root cause of the issue.

Types of Black Box Testing

Black box testing can be implemented to: functional, non-functional, and regression testing.

Functional Testing

Black box testing can test special functions or features of the software that are under test. It is possible to log in using correct user credentials, and not possible to log in using wrong inputs.

Functional testing aims on the most critical aspects of the software, on integration between key components or on the whole system (system testing).

Non-Functional Testing

Black box testing can check multiple ways of the software, beyond features and functionality. A non-functional test does not check if the software can perform a specific feature but it checks how it performs that action.

Black box tests software is:

  • Usable and easy to understand for its users
  • Performant under expected
  • Compatible with relevant devices, screen sizes or operating systems
  • Exposed to security vulnerabilities

Regression Testing

Black box testing can be used to check if a new version or build of the software executes a regression or degradation in capabilities from one build to the next. Regression testing can be implemented to functional aspects of the software (a specific feature no longer works as expected in the new version or build) or non-functional aspects.

Test design techniques

Typical black-box test design techniques include:

Equivalence Partition

Testers can separate possible inputs into groups or and test only one input credentials from each group. If a system requires a user’s information and provides the same response for all users that are under the age of 18, and a different response for users over 18, it is sufficient for testers to check one information is in the “under 18” group and one date in the “over 18” group.

Boundary Value Analysis

Testers can identify that a system has a specific response around a special boundary value.

Decision Table Testing

Many systems provide outputs based on a set of preconditions. Testers can then identify “rules” which are a combination of conditions, identify the outcome of each rule and design a test case for each rule.

State Transition Testing

In some system software, significant responses are created when the system transitions from one state to another. A common is a login mechanism which allows users to make the authentication, but after a specific number of attempts, locking the account.

If testers identify a state transition mechanism, they can design test cases that probe the system when it transitions states. For example, for a system that locks the account after 3 failed login attempts, a test case can check what happens at the fourth login attempt.

Error Guessing

This technique involves testing for common mistakes that developers make when building same systems. Testers can check if the developer handled values in a field, text in a numeric field or numbers in a text-only field —However it is possible to submit user inputs that includes executable code, which has security significance.

A specific type of error guessing is testing for known software vulnerabilities that can affect the system under test.

Hacking

In penetration testing, black-box testing refers to a method where a hacker has no knowledge of the system being attacked. The goal of a black-box penetration test is to simulate an external hacking or cyber attack.

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