Put the system in the desired state and store an output of that state, then output the state of the system and compare with the initial "verified" state output, if these match then the test pass, if not the test fails.
This method simplifies testing by eliminating the need to manually specify expected results for each test, instead relying on approved snapshots stored in source control.
## Sources
https://www.danclarke.com/snapshot-testing-with-verify