How to make plugin native "testable"?

I discovered that notifications plugin, which I wrote are dose not have button for send test message on settings page. In the same time this plugin looks like “testable” in Sentry’s terminology.

Class of plugin inherited from sentry.plugins.bases.notify.NotificationPlugin. Therefore it has native test_configuration method, which looks like required to be “testable” in code of IPlugin class:

def is_testable(self, **kwargs):
    Returns True if this plugin is able to be tested.
    return hasattr(self, 'test_configuration')

When I open Settings page of my plugin in web-browser, I see request to: And response looks like:

{“name”: “Telegram Notifications”, “isTestable”: true, “config”: […], “enabled”: true, “canDisable”: true, “assets”: [], “type”: “notification”, “id”: “sentry_telegram”, “metadata”: {}}

But button for send test message yet not appear :frowning:

Only one place in code of Sentry, where I found related template: /sentry/templates/sentry/partial/_form.html not help me to solve it. Looks like it template not quite actual.

If all it is result of my mistake - please, point me to source of problem.
If it some bug in Sentry - can anyone point to way for fix it and I will try to solve it (with pull request or other way).

Sentry version - 8.14.0.

Code of plugin.