Black box testing
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Black box testing takes an external perspective of the test object to derive test cases. These tests can be functional or non-functional, though usually functional. The test designer selects valid and invalid input and determines the correct output. There is no knowledge of the test object's internal structure.
This method of test design is applicable to all levels of development - unit, integration, system and acceptance. The higher the level, and hence the bigger and more complex the box, the more we're forced to use black box testing to simplify. While this method can uncover unimplemented parts of the specification, you can't be sure that all existent paths are tested.
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[edit] Test Design Techniques
Typical black box test design techniques include:
- Equivalence partitioning
- Boundary value analysis
- Decision table testing
- Pairwise testing
- State transition tables
- Domain analysis
- Use case testing
[edit] User Input Validation
User input must be validated to conform to expected values. For example, if the software program is requesting input on the price of an item, and is expecting a value such as 3.99, the software must check to make sure all invalid cases are handled. A user could enter the price as "-1" and achieve results contrary to the design of the program. Other examples of entries that be entered and cause a failure in the software include: "1.20.35", "Abc", "0.000001", and "999999999". These are possible test scenarios that should be entered for each point of user input.
Other domains, such as text input, need to restrict the length of the characters that can be entered. If a program allocates 30 characters of memory space for a name, and the user enters 50 characters, a buffer overflow condition can occur.
Typically when invalid user input occurs, the program will either correct it automatically, or display a message to the user that their input needs to be corrected before proceeding.
[edit] Hardware
Functional testing devices like power supplies, amplifiers, and many other simple function electrical devices is common in the electronics industry. Automated functional testing of specified characteristics is used for production testing, and part of design validation.
