Snapshot testing

What is snapshot testing?

Snapshot testing is a type of “output comparison” or “golden master” testing. These tests prevent regressions by comparing the current characteristics of an application or component with stored “good” values for those characteristics.

How Snapshot Testing Works

As the name suggests, Snapshot testing records take a snap of the system. In Jest, this would be a render tree. Then it compares the recorded snapshot in future executions.

Benefits of Snapshot testing

  • It introduces a clear pattern for testing the component render trees.
  • Easier to view code changes.
  • Easier to update when the component changes.
  • Allows conditional rendering tests.
  • Allows checking how components behave once you pass various combinations of props to them

Difference with functional/unit test

The main difference between snapshot testing and functional/unit tests is, snapshot tests never assert the correct behavior of the application functionality but does an output comparison instead.

My conclusion

Snapshot tests are easy to create and they are a great way to check that your application’s behavior isn’t changing unexpectedly during development. I’ve tested snapshot tests , but I still prefer functional/unit tests, because they bring me more security.

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