What is blackbox testing?

Blackbox testing, also called behavioral testing, is a software testing method in which the internal structure, design, and implementation of the item being tested are not known to the tester.

This method is named as it is​ because the software program (in the eyes of the tester) is like a black box whose internal contents are not visible to the tester.

This method attempts to find errors in the following categories:

• Incorrect and missing functions.
• Interface errors.
• Errors in data structures and external database access.
• Behavioral and performance errors.
• Initialization and termination errors.

Steps

1. The requirements and specifications of the system are examined.

2. The tester chooses a variety of inputs to check whether or not the executable program processes them correctly. The various inputs include valid inputs, invalid inputs, ​and extreme inputs.

3. The tester determines expected outputs for all of those inputs.

4. The tester constructs test cases with the selected inputs.

5. The test cases are executed.

6. The tester compares the actual outputs with the expected outputs.

7. Defects, if any, are fixed and the system is re-tested.