def METHOD_NAME(self):
    monitor = self._create_monitor()
    monitor_environment = self._create_monitor_environment(monitor)
    checkin = MonitorCheckIn.objects.create(
        monitor=monitor,
        monitor_environment=monitor_environment,
        project_id=self.project.id,
        date_added=monitor.date_added,
        status=CheckInStatus.IN_PROGRESS,
    )
    path = self.get_path(monitor, checkin)
    resp = self.client.post(
        path,
        {
            "file": SimpleUploadedFile(
                "log.txt", b"test log data", content_type="application/text"
            ),
        },
        format="multipart",
        **self.token_auth_headers,
    )
    assert resp.status_code == 200, resp.content
    checkin = MonitorCheckIn.objects.get(id=checkin.id)
    assert checkin.status == CheckInStatus.IN_PROGRESS
    file = File.objects.get(id=checkin.attachment_id)
    assert file.name == "log.txt"
    assert file.getfile().read() == b"test log data"
    resp = self.client.post(
        path,
        {
            "file": SimpleUploadedFile(
                "log.txt", b"test log data", content_type="application/text"
            ),
        },
        format="multipart",
        **self.token_auth_headers,
    )
    assert resp.status_code == 400
    assert resp.data["detail"] == "Check-in already has an attachment"