You can easily test an API Key you’ve created. First navigate to Application Settings:
Then choose the API Access tab. Any keys you have already created will be listed here. To be redirected to a pre-authorized testing environment, all you need to do is click the API Doc link located within the Key entry.
As stated, this link will redirect you to a pre-authorized testing environment. It will be authorized using specifically the API Key you clicked the link for. This means you can test things such as which specific endpoints are available from the given key’s permissions.