5.13. Keeping State in Extensions

Usually, an extension is instantiated only once. So the question becomes relevant: How do you keep the state from one invocation of an extension to the next? The ExtensionContext API provides a Store exactly for this purpose. Extensions may put values into a store for later retrieval. See the [TimingExtension](#extensions-lifecycle-callbacks-timing-extension) for an example of using the Store with a method-level scope. It is important to remember that values stored in an ExtensionContext during test execution will not be available in the surrounding ExtensionContext. Since ExtensionContexts may be nested, the scope of inner contexts may also be limited. Consult the corresponding Javadoc for details on the methods available for storing and retrieving values via the [Store](https://junit.org/junit5/docs/current/api/org.junit.jupiter.api/org/junit/jupiter/api/extension/ExtensionContext.Store.html).