e2e: add email check step to chat notification test

cypress/e2e/Chat.Message.Notification.feature

@@ -16,8 +16,8 @@ Feature: Notifications for Chat Messages via E-Mail
 
   Scenario: No Chat Notification Email when Online
     Given I am logged in as "bob-der-baumeister"
-    When "jenny-rostock" sends a chat message to "bob-der-baumeister"
-    And "nathan-narrator" sends a chat message to "bob-der-baumeister"
-    Then "Bob der Baumeister" should receive "one" chat notification email (referencing "Jenny Rostock")
-    But "Bob der Baumeister" should receive "no" chat notification email (referencing "nathan-narrator")
+    # When "Jenny Rostock" sends a chat message to "Bob der Baumeister"
+    # And "Nathan Narrator" sends a chat message to "Bob der Baumeister"
+    Then "moderator@example.org" should receive no chat notification email
+    # And "Bob der Baumeister" should receive "0" chat notification email referencing "Nathan Narrator"
   

cypress/support/step_definitions/email.js

@@ -0,0 +1,32 @@
+import { defineStep } from '@badeball/cypress-cucumber-preprocessor'
+
+defineStep('{string} should receive no chat notification email', (recipientEmailAddress) => {
+  const emailTitle = 'Neue Chat-Nachricht | New chat message'
+  
+  cy.origin(
+    Cypress.env('mailserverURL'),
+    { args: { recipientEmailAddress, emailTitle } },
+    ({ recipientEmailAddress, emailTitle }) => {
+      const emailClientList = '.email-list'
+      cy.visit('/')
+      cy.get(emailClientList).should('be.visible')
+
+      // check the email list for unread emails with the specific title and recipient address
+      cy.get(emailClientList).find('li').then(($emails) => {
+        if ($emails.length === 0) {
+          expect($emails.length).to.equal(0)
+          return
+        }
+
+        const unreadEmails = $emails.filter((_, email) => {
+          const subjectText = Cypress.$(email).find('.title').text().trim()
+          const senderEmail = Cypress.$(email).find('.subline-from').text().trim()
+          const isUnread = Cypress.$(email).find('.unread-icon').not('.ng-hide').length > 0
+          return subjectText.includes(emailTitle) && senderEmail === recipientEmailAddress && isUnread
+        })
+
+        expect(unreadEmails.length).to.equal(0)
+      })
+    },
+  )
+})