Mutation Testing

Techopedia explains Mutation Testing

Mutation testing is a simple but ingenious method used to validate source code correctness and the testing process. The concept was first coined by Richard Lipton in 1971, and there has been a surge of interest since that time.

Mutation testing's working mechanism is simple and straightforward. A piece of source code encompassing all unit tests is selected. After verifying all positive testing for a given source code, a mutation is introduced into the program.

The degree of mutation applied to a given code block may vary. A common mutation testing implementation involves replacing a logical operator with its inverse. For example, operator "! =" is used in place of "= =." In some cases, mutation involves rearranging lines to change the execution order or even deleting a few lines of code. Complex mutation testing levels may result in compilation errors.

Once a program is modified, a suite of unit tests are executed against the mutated code. The mutated code passes or fails the unit test, depending on the testing quality. A well-written unit test must detect mutated code errors, resulting in failure. A unit test that fails to detect code errors may require a rewrite.

Mutation testing facilitates the following advantages:

• Program code fault identification
• Effective test case development
• Detection of loopholes in test data
• Improved software program quality
• Elimination of code ambiguity

Disadvantages of mutation testing include:

• Difficult implementation of complex mutations
• Expensive and time-consuming
• Requires skilled testers with programming knowledge