Enable `maildev` SMTP server in CI for Cypress tests (#15665)

* Add SMTP server for testing

* Try running maildev in the default executor for Cypress

* Add first email-based Cypress test

* Try different ports

* Stop using ENVs for maildev

* Use camelCase for `const`

Co-authored-by: Luis Paolini <paoliniluis@gmail.com>

.circleci/config.yml

@@ -12,10 +12,12 @@ executors:
       - image: metabase/ci:lein-2.9.5-clojure-1.10.3.814
 
   # CircleCI base (Lein 2.9.5) + Node + Headless browsers + Clojure CLI - big one
+  # Maildev runs by default with all Cypress tests
   clojure-and-node-and-browsers:
     working_directory: /home/circleci/metabase/metabase/
     docker:
       - image: circleci/clojure:lein-2.9.5-node-browsers
+      - image: maildev/maildev
 
   # Java 11 tests also test Metabase with the at-rest encryption enabled. See
   # https://metabase.com/docs/latest/operations-guide/encrypting-database-details-at-rest.html for an explanation of

frontend/test/metabase/scenarios/admin/settings/settings.cy.spec.js

@@ -371,6 +371,26 @@ describe("scenarios > admin > settings", () => {
       cy.findByText("Sorry, something went wrong. Please try again.");
     });
 
+    it("should send a test email for a valid SMTP configuration", () => {
+      // We must clear maildev inbox before each run - this will be extracted and automated
+      cy.request("DELETE", "http://localhost:80/email/all");
+      cy.request("PUT", "/api/setting", {
+        "email-smtp-host": "localhost",
+        "email-smtp-port": "25",
+        "email-smtp-username": "admin",
+        "email-smtp-password": "admin",
+        "email-smtp-security": "none",
+        "email-from-address": "mailer@metabase.test",
+      });
+      cy.visit("/admin/settings/email");
+      cy.findByText("Send test email").click();
+      cy.findByText("Sent!");
+      cy.request("GET", "http://localhost:80/email").then(({ body }) => {
+        const emailBody = body[0].text;
+        expect(emailBody).to.include("Your Metabase emails are working");
+      });
+    });
+
     it("should be able to clear email settings", () => {
       cy.visit("/admin/settings/email");
       cy.findByText("Clear").click();