Why integration testing is harder than unit testing?

Before jumping right into understanding as to why integration testing is harder than unit testing, it is much better to first understand the differences between integration tests vs unit tests. Once the differences between integration tests vs unit tests are known, then it will be quite easy to know as to why integration testing is harder than unit testing.

Differences between unit testing vs Integration testing:

Unit testing:

• A single component of an application is checked

• It is narrow in scope as only small pieces of code known as units are tested

• It has no dependencies

• It cannot be divided into further types

• The testing process starts with the module specification

Integration testing:

• Two or more modules are integrated and then their behavior is analyzed

• It is wider in scope and the whole application under test is covered  and upon that much more effort is required to carry out testing

• It is dependent on other outside systems like hardware allocated for them, databases etc.

• It is divided into further types such as bottom-up integration, top-down integration, hybrid integration etc.

• The testing process starts with the interface specification
  
  

The information provided below will help a reader understand as to why integration testing is harder than unit testing:

The nature of the functionality being tested is one of the primary reasons that depicts as to why integration testing is more complex than unit testing. As the interface accuracy of several parts of an application is being checked, hence, there is a requirement for extensive setup to create and run the tests.

More defects than unit tests are revealed by integration tests and upon that the tester is required to build real-world user scenarios into their testing protocol.

Following are a few points that depict as to why integration testing is harder than unit testing:

• A variety of factors such as environment, platforms, database, etc., need to be managed accordingly

• The integration of a new system with a legacy system is being tested or two legacy systems are integrated which requires multiple changes.

There will be scenarios where too many permutations and paths are required for integration testing.