Bottom Up Approach

What is bottom up approach in testing?

For software testing using integration, the functionality of a software is divided into small independent modules. In this method, testing is carried out starting from the lowermost sub modules and gradually moves upwards towards the main module.

Performing bottom up testing approach with an example

A prominent feature of the bottom up approach is the use of small temporary programmes called DRIVERS to simulate the higher sub modules or the main module. Let us suppose that a software functionality needs to be tested with one main module 1 having sub modules 2&3 using the bottom up approach. The main module can be replaced by a driver and the testing is carried out on sub modules 2 and 3. The same strategy is utilised for other branches and drivers are used to simulate modules place higher in the hierarchy while testing is carried out on the lower sub modules. This approach proceeds upwards from the lowest of sub modules to the chief most module.

Advantages of bottom up approach

  • Development and testing can be taken care of side by side, enabling the end product to be fairly in sync with customer's requirement.
  • Test cases are simple to create.
  • The approach comes handy when trying to detect major flaws existing in the lower hierarchy of the program.

Disadvantages of bottom up approach

  • Since the main module is tested last, the key defects in interfaces related to the main module are tested in the end.
  • Test drivers are required to be created at all levels.
  • The product is not complete or ready for launch until the last addition of a module.
  • The test drivers themselves need to be tested before their deployment for bottom up approach. This increases the overall testing effort.