ui/doc: add cypress test for the documentation link

Refs: #2149

ui/cypress/integration/AccessDocumentation.feature

@@ -0,0 +1,4 @@
+Feature: AccessDocumentation
+ Scenario: Access documentation from the Navbar
+     Given I log in
+     Then I can access the documentation from the navbar

ui/cypress/integration/common/accessDocumentation.js

@@ -0,0 +1,21 @@
+import { Then } from 'cypress-cucumber-preprocessor/steps';
+
+Then('I can access the documentation from the navbar', () => {
+  const target_url = Cypress.env('target_url');
+
+  cy.visit(target_url, {
+    onBeforeLoad(win) {
+      // win is the the remote page's window object
+      // `cy.stub()` stubs the window.open method
+      cy.stub(win, 'open', url => {
+        expect(url).to.have.string('/docs/index.html');
+      });
+    },
+  });
+
+  cy.get('.sc-dropdown')
+    .eq(1)
+    .click();
+
+  cy.get('[data-cy = documentation]').click();
+});

ui/src/containers/Layout.js

@@ -63,6 +63,7 @@ const Layout = props => {
       onClick: () => {
         window.open(`${api.url_doc}/index.html`);
       },
+      'data-cy': 'documentation',
     },
   ];