Software Testing Methods

We discussed black box and white box testing in the earlier chapter. Here we explore three more testing methods:

• Gray Box Testing
• Incremental Testing
• Thread Testing

Gray Box Testing

Gray box testing, also spelled grey box testing, combines black box and white box techniques. It examines both the functional behavior and internal logic of the software. The tester has some knowledge of the code, rather than a complete understanding. Ideally, this includes knowledge of internal data structures and algorithms.

Gray box testing examines functional behavior and internal operation together. The tester should write thorough test cases using data that checks all possible internal logic.

Gray box testing requires you to understand the software’s functionality, architecture, data flow and exception handling. On large projects, automated tests can check functionality and the user interface, saving time and reducing pressure on testers.

Incremental Testing

Incremental testing follows unit testing and checks how independent modules interact during integration. Developers integrate modules systematically, using stubs or drivers where needed. This approach to integration testing has three main forms:

1. Top-down integration: Integrate modules from the top down, replacing unavailable lower-level modules with stubs.
2. Bottom-up integration: Integrate modules from the bottom up, using drivers in place of unavailable higher-level modules.
3. Functional incremental integration: Integrate and test modules according to the functional specification documents.

Incremental testing helps uncover defects early. Its drawback is the time needed to develop stubs and drivers.

Thread Testing

Thread testing is used for applications with a client-server architecture. Here, a thread means a small sequence of work that performs a required functional task or transaction. Early in integration, check that these tasks and transactions work as required. Integrate and test threads incrementally at the subsystem level, then at the system level.