Given rather unusual nature of this app (core functionality revolving around notifying an external system via HTTP POST requests), it seems that the most reasonable way to automate testing would rely on e2e approach. A draft solution would be to create a separate Node.js server used as a webhook target (performing assertions on received data) with events triggered by simulated frontend user activity automated via Cypress. Such pipeline would allow for quicker delivery of updates for newer Nextcloud versions, as they wouldn't have to be tested manually.
Given rather unusual nature of this app (core functionality revolving around notifying an external system via HTTP POST requests), it seems that the most reasonable way to automate testing would rely on e2e approach. A draft solution would be to create a separate Node.js server used as a webhook target (performing assertions on received data) with events triggered by simulated frontend user activity automated via Cypress. Such pipeline would allow for quicker delivery of updates for newer Nextcloud versions, as they wouldn't have to be tested manually.