What is Incremental testing in software?

The incremental testing approach has the advantage that the defects are found early in a smaller assembly when it is relatively easy to detect the cause.

• Another advantage is that all programmers are integrated one by one, and a test is carried out after each step. 
• A disadvantage is that it can be time-consuming since stubs and drivers have to be developed and used in the test.
• Within incremental integration testing a range of possibilities exist, partly depending on the system architecture:
  • Top down: Testing takes place from top to bottom, following the control flow or architectural structure (e.g. starting from the GUI or main menu). Components or systems are substituted by stubs.
  • Bottom up: Testing takes place from the bottom of the control flow upwards. Components or systems are substituted by drivers.
  • Functional incremental: Integration and testing  takes place on the basis of the functions and functionalities, as documented in the functional specification.