Integration Testing:

Integration Testing:
Objective
 The primary objective of integration testing is to discover errors in the interfaces between Modules/Sub-Systems (Host & Client Interfaces).
 Minimizing the errors which include internal and external Interface errors
Approach:

Top-Down Approach

The integration process is performed in a series of 5 steps
1. The main control module is used as a test driver, and stubs are substituted for all modules directly subordinate to the main control module.
2. Depending on the integration approach selected (depth or breadth-first) subordinate stubs are replaced at a time with actual modules.
3. Tests are conducted as each module is module is integrated.
4. One completion of each set of tests, another stub is replaced with the real-module.
5. Regression testing may be conducted to ensure that new errors have not been introduced.
Advantages
 We can verify the major controls early in the testing Process
Disadvantage:
 Stubs are required. Very difficult to develop stubs
Bottom-Up Approach.


A bottom-up integration strategy may be implemented with the following steps:
1. Low level modules are combined into clusters (Some times called builds) that perform a specific software sub function.
2. A driver (control program for testing) is written to coordinate test case input and output.
3. The cluster is tested.
4. Drivers are removed and clusters are combined upward in the program structure
Advantages
 Easy to Develop the drivers than stubs
Disadvantage:
 The need of test drivers
 Late detection of interface problems
An integration testing is conducted, the tester should identify critical modules. A critical module has one or more of the following characteristics:

1. Address several software requirements.
2. Has a high-level of control. (resides relatively high in the program structure)
3. Complex & Error-Phone.
4. Have definite performance requirements.
Testing activities in Integration Testing Phase
1. This testing is conducted in parallel with integration of various applications (or components)
2. Testing the product with its external and internal interfaces without using drivers and stubs.
3. Incremental approach while integrating the interfaces.