Persistence testing checks whether durable data survives beyond the immediate interface state. It can cover browser refreshes, application restarts, new sessions and synchronization between different views.
A page may appear to save a change even when only temporary local state was updated. Refreshing and re-reading the record helps confirm that the intended storage layer actually retained it.
ELI5
Persistence testing checks whether an application really remembers what was saved. Information should not vanish when the page closes or reloads.
For example, after changing a profile name, the tester refreshes the browser and confirms that the new name still appears.
