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How is snapshot testing different from unit 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. Snapshot tests are fundamentally different from unit and functional tests.
What is snapshot testing and what does it do?
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.
What happens when a snapshot doesn’t pass?
On subsequent test runs Jest will simply compare the rendered output with the previous snapshot. If they match, the test will pass. If they don’t match, either the test runner found a bug in your code that should be fixed, or the implementation has changed and the snapshot needs to be updated.
How does end to end snapshot testing work?
Next time the test runner executes the test, it will load the value from the snapshot and compare it with the received value. If they are equal (deep equality is used), the assertion passes. If they are different, the assertion throws an error.
How are inline snapshots similar to.snap files?
Inline snapshots behave identically to external snapshots ( .snap files), except the snapshot values are written automatically back into the source code. This means you can get the benefits of automatically generated snapshots without having to switch to an external file to make sure the correct value was written.
Do you have to test all snapshots in CI?
It is expected that all snapshots are part of the code that is run on CI and since new snapshots automatically pass, they should not pass a test run on a CI system. It is recommended to always commit all snapshots and to keep them in version control. Should snapshot files be committed?