add cypress guest-routes spec

frontend/blog_portal/cypress/e2e/guest_routes.cy.ts

@@ -0,0 +1,41 @@
+describe("guest route guards", function () {
+  beforeEach(function () {
+    cy.resetDb();
+    cy.clearMail();
+  });
+
+  it("redirects anonymous visitors away from /users/:displayName/posts/new", function () {
+    cy.visit("/users/alice/posts/new");
+    cy.location("pathname").should("eq", "/login");
+  });
+
+  it("redirects authenticated visitors away from /login", function () {
+    cy.seedConfirmedUser({
+      email: "alice@example.com",
+      displayName: "alice",
+      password: "longenoughpassword",
+    });
+    cy.loginViaApi({
+      email: "alice@example.com",
+      password: "longenoughpassword",
+    });
+
+    cy.visit("/login");
+    cy.location("pathname").should("eq", "/");
+  });
+
+  it("redirects authenticated visitors away from /signup", function () {
+    cy.seedConfirmedUser({
+      email: "alice@example.com",
+      displayName: "alice",
+      password: "longenoughpassword",
+    });
+    cy.loginViaApi({
+      email: "alice@example.com",
+      password: "longenoughpassword",
+    });
+
+    cy.visit("/signup");
+    cy.location("pathname").should("eq", "/");
+  });
+});