Custom matchers

[deyceg]

Hey guys,

Great little tool and was wondering whether or not you had any plans to support custom matchers to only diff a subset of the snapshot tree?

My use case is pretty much https://www.npmjs.com/package/jest-cdk-snapshot.

[jackmatt2]

Yes - we do support this. It's called a snapshot comparator

see: https://github.com/origin-energy/java-snapshot-testing#supplying-a-custom-snapshotcomparator

[deyceg]

@jackmatt2 Thanks I ended up writing my own comparator, serializer and reporter in the end to get it working. I think it would have been a little easier if these interfaces were generic as I had to do a bit of massaging of types to get it to behave the way I wanted it to (compare a subsection of the actual against the snapshot based on a predicate).

[jackmatt2]

I'm doing quite a bit of refactoring in this area. Can you give some examples of API changes that may have made this easier for you?

[jackmatt2]

@deyceg In 4.0.0, I have changed the interface to make it more usable (... I think). It now accepts a "Snapshot" class.

You can also add headers to inject metadata around your snapshot - this may make your logic in your comparator/serializer much simpler. For example you might like to store the class name of the object before serializing it .header('className', obj.getClass().getName()), then in your comparator load based on the header value.