Difference Between Top-Down and Bottom-Up Integration Testing

In this post, we will understand the difference between top-down integration testing and bottom-up integration testing −

Top-down Integration Testing

• It is also known as incremental integration testing.

• The higher level modules are first tested after which the lower level modules are tested.

• Once it is done, they are integrated.

• The higher level modules are the main modules and the lower level modules are the submodules.

• It uses stubs to simulate the sub-modules.

• If the sub-module hasn’t been fully developed, the stub acts like a replacement to it.

• It is useful in cases where significant defect occurs at the top of the program.

• The main module is designed first and then the submodules or subroutines are called from it.

• It is implemented on structure or procedure-oriented programming languages.

• It is a simple testing technique.

• It works on big to small components.

• Stub modules need to be produced.

Here’s the flow diagram for stub −

Bottom-up Integration Testing

• The lower level modules are tested first after which the higher level modules are tested.

• The lower level modules are the sub-modules and higher level modules are the main modules.

• It uses test drivers to initiate and pass the required data to the sub-modules.

• The test drivers are used to simulate the main module.

• If the main module hasn’t been developed yet, the driver works as a replacement to it.

• It is useful in cases where the crucial flaws are identified at the bottom of the program.

• It is generally implemented on object-oriented programming languages.

• It is highly complex and data intensive.

• It works on small to big components.

• The driver modules need to be produced.

Here’s the flow diagram −