# Black Box Testing

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Black box testing is also referred to as specification-based testing. It involves performing testing based on the specification of the system under test. Unlike white-box testing, the knowledge of the internal architecture and the application code is not required in black-box testing.

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## Black Box Testing Definition

Black box testing is the type of testing in which an application is tested based on its requirements specifications without the need for knowledge of its internal architecture.

## Features of Black Box Testing

• It tests both functional as well as non-functional requirements of the application.
• Knowledge/access to the coding/design/internal architecture of the software is not required.
• Testers can work independently from developers thus ensuring unbiased and end-user centric testing.

## Black Box Testing Techniques

Following are some of the most common types of black-box testing techniques.

### Equivalence class partitioning

Equivalence class partitioning involves partitioning the input data into logical groups or equivalence classes. All the data items lying in an equivalence class are assumed to be processed in the same way by the application when passed as input.

E.g. for software that finds the square of a number, we can have different equivalence classes like – all positive numbers, negative numbers, decimal numbers, negative decimal numbers, etc.

Its advantage is – the overall test execution time reduces as the number of test data greatly reduces.

### Boundary value analysis

Boundary value analysis, is a black-box testing technique, closely associated with equivalence class partitioning. In this technique, we analyze the behavior of the application with test data residing at the boundaries of the equivalence classes.

E.g. for equivalence classes with an input between 0 to 100, the test data using boundary value analysis would be 0 and 100.

Its advantage is – it is easier and faster to find defects as the density of defects at boundaries is more.

### Decision tables

Decision tables testing is used to test the application’s behavior based on a different combination of input values. A decision table has a different set of input combinations and their corresponding expected outcomes on each row.

### Cause-effect graph

A cause-effect graph testing is carried out using a graphical representation of input i.e. cause and output i.e. effect. We can find the coverage of cause-effect graphs based on the percentage of combinations of inputs tested out of the total possible combinations.

### State transition testing

The state transition testing is based on a state machine model. In this technique, we test the application by graphically representing the transition between the different states of the application based on the different events and actions.

### Use case testing

Use case testing is a type of testing that is carried out using use cases. In this technique, we test the application using use-cases, representing the interaction of the application with the different actors.

## How to do black-box testing?

After learning black box testing techniques, let us learn the different steps involved in a typical black-box test.

• The first step is to check the requirement specifications provided by the application. The requirements should be provided in a properly documented SRS file.

• Tester collects the different positive test scenarios and negative test scenarios to verify if the system under test processes them correctly. This ensures good test coverage.

• The test cases are executed and the output is validated against the expected results. This process is to mark the pass or fail of the test result.

• The failed test cases are sent back to the development team to fix the bugs.

• After the fix, a retest is conducted to check and ensure all the test cases run successfully.

1. Tests are performed from the user’s point of view. So, there is higher chance of meeting customer’s expectations.

2. There is unbiased testing as both the tester and the developer work independently.

3. It is suitable for the testing of very large systems.

4. There is no need for any technical knowledge or language specification.

5. Test cases can be designed as soon as the requirements are finalized.

## Black box vs White box testing

The difference between black-box testing and white-box testing is one of the most common testing interview questions. Both are equally important and performed according to the situation. Here are a few differences to bring clarity to both techniques.

With this, we have come to the end of this tutorial. If you have any questions, please ask in the comment section. Also, check out our complete software testing tutorial below.

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