Every software tester from independent software testing companies in USA and Europe knows about test levels when developing a software product. There are four of them, and each test level requires its test objectives.

A dedicated testing team should create the appropriate tests which detect defects that are specific to each level. Software testing team also configure the test environment and all the necessary tools.

Basic Test Levels:

• Component/Unit testing.
• Integration testing.
• System testing.
• Acceptance testing.

Component/ Unit Testing

Component/Unit testing is the testing service that validates individual components of the software. Depending on the implementation of the software product, there is a chance to check various parts of the program individually and independently (objects, classes, functions, modules). As a rule, on the given test level testers verify only a particular part of the functionality and for all software emulations they use stubs, drivers, and simulators. Defect detection and their fixing in this program decomposition on the early stages allows avoiding a further influence of the error on another product functionality.

Baseline Testing for Component Testing are:

• Component Requirements.
• Detailed Design.
• Code.

Unit testing is not that formal than other test levels. The primary objective – is the fast feedback about program components being healthy/unhealthy. In the case of malfunctions, programmers should rapidly localizing the problem, correct the defect and provide a new version for testing.