set up pages in UI

ui/src/tbd/ui/db.cljs

@@ -2,7 +2,9 @@
   (:require [tbd.ui.tictactoe :as tictactoe]))
 
 (def default-db
-  {:calc {:x "" :y ""
+  {;; The page being shown (see tbd.ui.pages); it follows the URL's fragment.
+   :page :games
+   :calc {:x "" :y ""
           ;; {:status :idle}
           ;; {:status :loading}
           ;; {:status :ok :x "2" :y "3" :sum 5}
@@ -19,7 +21,7 @@
            :items []
            :new-title ""
            :error nil}
-   ;; The "Add this MCP server to Claude Code" section: :copied? is true right after the
+   ;; The "Add this MCP server to Claude Code" page: :copied? is true right after the
    ;; command was copied to the clipboard.
    :mcp {:copied? false}
    ;; Tic-tac-toe, entirely client side: the board (see tbd.ui.tictactoe) and whose turn it is.

ui/src/tbd/ui/events.cljs

@@ -3,6 +3,7 @@
             [clojure.string :as str]
             [re-frame.core :as rf]
             [tbd.ui.db :as db]
+            [tbd.ui.pages :as pages]
             [tbd.ui.tictactoe :as tictactoe]))
 
 ;; Effect: request `uri` (GET unless `method` is given), then dispatch
@@ -21,12 +22,54 @@
                                                          :body %})))))
         (.catch #(rf/dispatch (conj on-response {:ok? false :status nil :body (.-message %)}))))))
 
+;; Coeffect: the URL's fragment, which says which page to start on.
+(rf/reg-cofx
+  ::hash
+  (fn [cofx _]
+    (assoc cofx :hash js/location.hash)))
+
+;; Effect: show the page the URL names whenever it changes (a link was followed, or Back and
+;; Forward were pressed). Only one listener is ever installed, however often this runs.
+(defonce ^:private hash-listener (atom nil))
+
+(rf/reg-fx
+  ::listen-for-hash
+  (fn [_]
+    (when-let [old @hash-listener]
+      (.removeEventListener js/window "hashchange" old))
+    (reset! hash-listener #(rf/dispatch [::hash-changed js/location.hash]))
+    (.addEventListener js/window "hashchange" @hash-listener)))
+
+;; Effect: put `hash` in the URL, which is how a page gets its own address (and a Back button).
+(rf/reg-fx
+  ::set-hash
+  (fn [hash]
+    (set! js/location.hash hash)))
+
 (rf/reg-event-fx
   ::initialize
-  (fn [_ _]
-    {:db db/default-db
+  [(rf/inject-cofx ::hash)]
+  (fn [{:keys [hash]} _]
+    {:db (assoc db/default-db :page (pages/hash->page hash))
+     ::listen-for-hash true
      :dispatch [::load-user]}))
 
+;; --- Pages ---
+
+;; The URL changed (a link was followed, or Back was pressed): show the page it names.
+(rf/reg-event-db
+  ::hash-changed
+  (fn [db [_ hash]]
+    (assoc db :page (pages/hash->page hash))))
+
+;; Go to a page without a link, as the browser tools do. The page changes right away; the URL
+;; follows, and its change event finds the page already shown.
+(rf/reg-event-fx
+  ::navigate
+  (fn [{:keys [db]} [_ page]]
+    {:db (assoc db :page page)
+     ::set-hash (pages/page->hash page)}))
+
 (rf/reg-event-db
   ::set-operand
   (fn [db [_ k value]]
@@ -169,7 +212,7 @@
       {:db (update-in db [:todos :items] (fn [items] (filterv #(not= id (:id %)) items)))}
       {:dispatch [::todo-failed resp]})))
 
-;; --- MCP setup section ---
+;; --- MCP setup page ---
 
 ;; Effect: put `text` on the clipboard. The Clipboard API only exists on secure origins (https
 ;; or localhost), so the view doesn't offer the button without it; failures are ignored.

ui/src/tbd/ui/pages.cljs

@@ -0,0 +1,27 @@
+(ns tbd.ui.pages
+  "The pages of the app, and how they map to the URL. The server only serves the shell at `/`,
+  so a page lives in the fragment (`/#/todos`): following a link between pages never asks the
+  server for anything, and a page can still be bookmarked or reloaded.")
+
+(def pages
+  "The pages in the order of the tabs: {:id :title :login?}. :login? pages are only offered
+  (and only show anything) to someone who is logged in."
+  [{:id :games :title "Games"}
+   {:id :todos :title "Todos" :login? true}
+   {:id :ai-setup :title "AI setup"}])
+
+(def default-page (:id (first pages)))
+
+(def ^:private ids (into #{} (map :id) pages))
+
+(defn page->hash
+  "The fragment that opens `page`: \"#/todos\"."
+  [page]
+  (str "#/" (name page)))
+
+(defn hash->page
+  "The page a fragment (with or without its leading #) opens; the default page when it is empty
+  or names no page."
+  [hash]
+  (let [id (keyword (second (re-find #"^#?/?([^/?]*)" (or hash ""))))]
+    (if (contains? ids id) id default-page)))

ui/src/tbd/ui/subs.cljs

@@ -2,6 +2,7 @@
   (:require [re-frame.core :as rf]
             [tbd.ui.tictactoe :as tictactoe]))
 
+(rf/reg-sub ::page (fn [db _] (:page db)))
 (rf/reg-sub ::operand (fn [db [_ k]] (get-in db [:calc k])))
 (rf/reg-sub ::result (fn [db _] (get-in db [:calc :result])))
 (rf/reg-sub ::user (fn [db _] (:user db)))

ui/src/tbd/ui/views.cljs

@@ -2,6 +2,7 @@
   (:require [clojure.string :as str]
             [re-frame.core :as rf]
             [tbd.ui.events :as events]
+            [tbd.ui.pages :as pages]
             [tbd.ui.subs :as subs]
             [tbd.ui.webmcp :as webmcp]))
 
@@ -23,15 +24,17 @@
   "Sends GET /api/add?x=..&y=.. on submit and shows the sum the server returns."
   []
   (let [result @(rf/subscribe [::subs/result])]
-    [:form {:on-submit (fn [e]
-                         (.preventDefault e)
-                         (rf/dispatch [::events/add]))}
-     [:div {:style {:display "flex" :gap "1rem" :align-items "center"}}
-      [operand-input :x "x"]
-      "+"
-      [operand-input :y "y"]
-      [:button {:type "submit" :disabled (= :loading (:status result))} "Add"]]
-     [result-line result]]))
+    [:section
+     [:h2 "Calculator"]
+     [:form {:on-submit (fn [e]
+                          (.preventDefault e)
+                          (rf/dispatch [::events/add]))}
+      [:div {:style {:display "flex" :gap "1rem" :align-items "center"}}
+       [operand-input :x "x"]
+       "+"
+       [operand-input :y "y"]
+       [:button {:type "submit" :disabled (= :loading (:status result))} "Add"]]
+      [result-line result]]]))
 
 (defn- todo-item [{:keys [id title done]}]
   [:li {:style {:display "flex" :gap "0.5rem" :align-items "center" :margin "0.25rem 0"}}
@@ -52,7 +55,7 @@
              ^{:key (:id todo)} [todo-item todo])]))
 
 (defn todos
-  "Your todos (GET/POST /api/todos, PATCH/DELETE /api/todos/:id). Only shown when logged in."
+  "Your todos (GET/POST /api/todos, PATCH/DELETE /api/todos/:id)."
   []
   (let [{:keys [new-title error] :as state} @(rf/subscribe [::subs/todos])]
     [:section
@@ -105,20 +108,13 @@
   []
   (str "claude mcp add --transport http tbd " js/location.origin "/mcp"))
 
-(defn- collapsible
-  "A section the reader can fold away by its heading (a native <details>, closed to start with)."
-  [title & body]
-  (into [:details {:style {:margin-top "2rem"}}
-         [:summary {:style {:cursor "pointer"}}
-          [:h2 {:style {:display "inline"}} title]]]
-        body))
-
 (defn mcp-setup
   "How to add this server to Claude Code: a command to copy, then signing in once."
   []
   (let [command (mcp-command)
         copied? @(rf/subscribe [::subs/mcp-copied?])]
-    [collapsible "Add this MCP server to Claude Code"
+    [:section
+     [:h2 "Add this MCP server to Claude Code"]
      [:p "Run this in your terminal:"]
      [:div {:style {:display "flex" :gap "0.5rem" :align-items "flex-start"}}
       [:pre {:style {:flex 1 :margin 0 :padding "0.75rem" :overflow-x "auto"
@@ -139,7 +135,8 @@
   "The page's own tools for a browser agent (WebMCP, see tbd.ui.webmcp): how to connect an MCP
   client to them. The token is pasted into the WebMCP widget in the corner of the page."
   []
-  [collapsible "Browser tools (WebMCP)"
+  [:section
+   [:h2 "Browser tools (WebMCP)"]
    [:p "This page offers " [:strong (count webmcp/tools)] " tools of its own (the calculator, the todos and the tic-tac-toe game) to "
     "your MCP client, over " [:a {:href "https://webmcp.dev" :target "_blank" :rel "noreferrer"} "WebMCP"]
     ", and you see them work on the page. To connect:"]
@@ -168,16 +165,42 @@
                 "Log out"]
     nil))
 
+(defn- login-prompt
+  "What the todos page says to someone who isn't logged in (nothing while we don't know yet)."
+  [{:keys [status message]}]
+  (case status
+    :anonymous [:section
+                [:h2 "Todos"]
+                [:p [:a {:href "/auth/login"} "Log in"] " to see your todos."]]
+    :error [:p {:role "alert" :style {:color "crimson"}} message]
+    nil))
+
+(defn- current-page [page user]
+  (case page
+    :games [:<> [tic-tac-toe] [calculator]]
+    :todos (if (= :logged-in (:status user)) [todos] [login-prompt user])
+    :ai-setup [:<> [mcp-setup] [browser-tools]]))
+
+(defn- tabs
+  "One link per page, the current one marked. The todos are only offered when logged in."
+  [current user]
+  [:nav {:aria-label "Pages" :style {:display "flex" :flex-wrap "wrap" :gap "1rem"
+                                     :border-bottom "1px solid GrayText" :padding-bottom "0.5rem"}}
+   (for [{:keys [id title login?]} pages/pages
+         :when (or (not login?) (= :logged-in (:status user)))]
+     ^{:key id}
+     [:a (cond-> {:href (pages/page->hash id)}
+           (= id current) (assoc :aria-current "page" :style {:font-weight "bold"}))
+      title])])
+
 (defn app []
-  (let [user @(rf/subscribe [::subs/user])]
+  (let [page @(rf/subscribe [::subs/page])
+        user @(rf/subscribe [::subs/user])]
     [:main {:style {:font-family "system-ui, sans-serif" :max-width "40rem" :margin "2rem auto"}}
      [:h1 "tbd"]
-     [calculator]
-     (when (= :logged-in (:status user))
-       [todos])
-     [tic-tac-toe]
-     [mcp-setup]
-     [browser-tools]
-     [:p [:a {:href "/api-docs"} "API docs"] " · " [:a {:href "/swagger.json"} "swagger.json"]
+     [tabs page user]
+     [current-page page user]
+     [:p {:style {:margin-top "2rem"}}
+      [:a {:href "/api-docs"} "API docs"] " · " [:a {:href "/swagger.json"} "swagger.json"]
       (when-let [link (auth-link user)]
         [:<> " · " link])]]))

ui/src/tbd/ui/webmcp.cljs

@@ -26,6 +26,12 @@
 
 (defn- fail! [message] (throw (js/Error. message)))
 
+(defn- show!
+  "Opens `page` (see tbd.ui.pages), the way a user would click its tab, so a tool that acts on
+  the page does it where it can be seen."
+  [page]
+  (rf/dispatch-sync [::events/navigate page]))
+
 (defn- settled
   "A promise of the app-db as soon as `(pred db)` holds (right away if it already does), or a
   rejection after `timeout-ms`. Requests made by events finish some time after the event is
@@ -117,6 +123,7 @@
     (fail! "invalid arguments: x and y must be numbers"))
   (when (= :loading (get-in (db) [:calc :result :status]))
     (fail! "an addition is already in progress"))
+  (show! :games)
   (rf/dispatch-sync [::events/set-operand :x (str x)])
   (rf/dispatch-sync [::events/set-operand :y (str y)])
   (rf/dispatch-sync [::events/add])
@@ -142,6 +149,7 @@
     (fail! "invalid arguments: title must be a non-empty string"))
   (-> (logged-in-todos)
       (.then (fn [_]
+               (show! :todos)
                (rf/dispatch-sync [::events/set-new-title title])
                ;; The field is emptied when the todo was added; a failure leaves it as it is.
                (change-todos [::events/add-todo] #(= "" (get-in % [:todos :new-title])) "the new todo")))
@@ -156,6 +164,7 @@
   (-> (logged-in-todos)
       (.then (fn [items]
                (let [todo (find-todo! items id)]
+                 (show! :todos)
                  (if (= done (boolean (:done todo)))
                    todo
                    (-> (change-todos [::events/set-done id done]
@@ -170,6 +179,7 @@
   (-> (logged-in-todos)
       (.then (fn [items]
                (find-todo! items id)
+               (show! :todos)
                (change-todos [::events/delete-todo id]
                              #(nil? (find-todo (get-in % [:todos :items]) id))
                              "the todo to go")))
@@ -208,12 +218,14 @@
       (fail! (str "it is " (name turn) "'s turn, not " player "'s")))
     (when (board cell)
       (fail! (str "cell " cell " is taken")))
+    (show! :games)
     (rf/dispatch-sync [::events/ttt-move cell])
     (tic-tac-toe-state)))
 
 (defn- new-tic-tac-toe-game
   "Presses New game."
   [_]
+  (show! :games)
   (rf/dispatch-sync [::events/ttt-reset])
   (tic-tac-toe-state))
 

ui/test/tbd/ui/core_test.cljs

@@ -21,6 +21,7 @@
 
 (use-fixtures :each
   tu/fake-server-fixture
+  tu/url-fixture
   {:before (fn []
              (reset! @#'webmcp/widget nil)
              ;; The widget logs every tool it registers. (Not console.log as a whole: that is
@@ -57,7 +58,7 @@
             (-> (ping #js {})
                 (.then (fn [result] (is (= "pong" (.. result -content (at 0) -text))))))))
         (fn []
-          (tu/shows "it found out who is logged in, and shows the todos" "section h2" "Todos"))
+          (tu/eventually (fn [] (some #(= "Todos" (.-textContent %)) (tu/q-all "nav a")))))
         (fn []
           (is (= :logged-in (get-in @rf-db/app-db [:user :status])))
           ;; The hot-reload hook redraws and registers the tools again, without starting over.

ui/test/tbd/ui/events_test.cljs

@@ -18,6 +18,7 @@
   (fn [value] (swap! effects conj [id value])))
 
 (use-fixtures :each
+  tu/url-fixture
   {:before (fn [] (reset! effects []) (reset! queued []))}
   (tu/stub-effects-fixture {::events/fetch (record ::events/fetch)
                             ::events/copy-to-clipboard (record ::events/copy-to-clipboard)
@@ -75,6 +76,28 @@
   (testing "it asks who is logged in"
     (is (= [{:uri "/auth/me" :on-response [::events/user-response]}] (requests)))))
 
+;; --- Pages ---
+
+(deftest initialize-opens-the-page-in-the-url-test
+  (set! js/location.hash "#/ai-setup")
+  (dispatch! [::events/initialize])
+  (is (= :ai-setup (:page (app-db)))))
+
+(deftest hash-changed-test
+  (start!)
+  (reset! effects [])
+  (dispatch! [::events/hash-changed "#/todos"])
+  (is (= :todos (:page (app-db))))
+  (dispatch! [::events/hash-changed "#/nowhere"])
+  (is (= :games (:page (app-db))) "an unknown address shows the first page")
+  (is (= [] (requests)) "changing the page asks the server for nothing"))
+
+(deftest navigate-test
+  (start!)
+  (dispatch! [::events/navigate :ai-setup])
+  (is (= :ai-setup (:page (app-db))) "the page changes at once")
+  (is (= "#/ai-setup" js/location.hash) "and gets its address"))
+
 ;; --- Calculator ---
 
 (deftest set-operand-test

ui/test/tbd/ui/pages_test.cljs

@@ -0,0 +1,26 @@
+(ns tbd.ui.pages-test
+  (:require [cljs.test :refer [deftest is testing]]
+            [tbd.ui.pages :as pages]))
+
+(deftest page->hash-test
+  (is (= "#/games" (pages/page->hash :games)))
+  (is (= "#/ai-setup" (pages/page->hash :ai-setup))))
+
+(deftest hash->page-test
+  (testing "every page has an address that opens it"
+    (doseq [{:keys [id]} pages/pages]
+      (is (= id (pages/hash->page (pages/page->hash id))))))
+  (testing "with or without the #"
+    (is (= :todos (pages/hash->page "#/todos")))
+    (is (= :todos (pages/hash->page "/todos")))
+    (is (= :todos (pages/hash->page "todos"))))
+  (testing "what follows the page's name is ignored"
+    (is (= :todos (pages/hash->page "#/todos/1?a=b"))))
+  (testing "no page, or an unknown one, is the first page"
+    (is (= :games pages/default-page))
+    (doseq [hash [nil "" "#" "#/" "#/nowhere" "#/Todos"]]
+      (is (= :games (pages/hash->page hash)) (pr-str hash)))))
+
+(deftest pages-test
+  (is (= [:games :todos :ai-setup] (mapv :id pages/pages)) "the order of the tabs")
+  (is (= [:todos] (mapv :id (filter :login? pages/pages)))))

ui/test/tbd/ui/subs_test.cljs

@@ -23,16 +23,19 @@
 (deftest plain-subs-test
   (testing "a new page"
     (is (= "" (sub [::subs/operand :x])))
+    (is (= :games (sub [::subs/page])))
     (is (= {:status :idle} (sub [::subs/result])))
     (is (= {:status :unknown} (sub [::subs/user])))
     (is (= (:todos db/default-db) (sub [::subs/todos])))
     (is (false? (sub [::subs/mcp-copied?]))))
   (testing "they follow the db"
+    (db! assoc :page :todos)
     (db! assoc-in [:calc :x] "4")
     (db! assoc-in [:calc :result] {:status :ok :x "4" :y "1" :sum 5})
     (db! assoc :user {:status :logged-in :login "alice"})
     (db! assoc-in [:todos :items] [{:id 1 :title "a"}])
     (db! assoc-in [:mcp :copied?] true)
+    (is (= :todos (sub [::subs/page])))
     (is (= "4" (sub [::subs/operand :x])))
     (is (= 5 (:sum (sub [::subs/result]))))
     (is (= "alice" (:login (sub [::subs/user]))))

ui/test/tbd/ui/test_util.cljs

@@ -76,6 +76,12 @@
    :after (fn []
             (aset js/globalThis "fetch" real-fetch))})
 
+(def url-fixture
+  "Each test starts on the page's own address, with no fragment (the page shown is the first)."
+  (let [reset-hash! #(set! js/location.hash "")]
+    {:before reset-hash!
+     :after reset-hash!}))
+
 (defn log-in! [] (swap! server assoc :user {:login "alice" :id 7}))
 
 ;; --- Stubbing re-frame effects ---

ui/test/tbd/ui/views_test.cljs

@@ -7,21 +7,29 @@
             [re-frame.db :as rf-db]
             [tbd.ui.db :as db]
             [tbd.ui.events :as events]
+            [tbd.ui.pages :as pages]
             [tbd.ui.test-util :as tu :refer [q q-all text shows steps click! type! submit!]]
             [tbd.ui.views :as views]
             [tbd.ui.webmcp :as webmcp]))
 
 (use-fixtures :each
   tu/fake-server-fixture
+  tu/url-fixture
   tu/page-fixture
   ;; The Copy button's 2 seconds are up when the test says so (see mcp-copy-button-test).
   (tu/stub-effects-fixture {:dispatch-later (fn [_])}))
 
 (defn- open-page!
-  "Starts the app as core/init does, minus the WebMCP widget."
-  []
-  (rf/dispatch-sync [::events/initialize])
-  (tu/mount! [views/app]))
+  "Starts the app as core/init does, minus the WebMCP widget, on the page whose address is
+  `page` (the first, when there is none)."
+  ([] (open-page! nil))
+  ([page]
+   (when page (set! js/location.hash (pages/page->hash page)))
+   (rf/dispatch-sync [::events/initialize])
+   (tu/mount! [views/app])))
+
+(defn- tab-titles []
+  (mapv #(.-textContent %) (q-all "nav a")))
 
 (defn- todos-section
   "The todos, which are only on the page when someone is logged in."
@@ -39,7 +47,7 @@
   [todos]
   (tu/log-in!)
   (swap! tu/server assoc :todos todos :next-id (inc (count todos)))
-  (steps open-page!
+  (steps #(open-page! :todos)
          #(tu/eventually todos-section)
          #(tu/eventually (fn [] (or (q "ul li") (= "Nothing to do." (text "section > p")))))))
 
@@ -59,8 +67,8 @@
           (is (= ["API docs" "swagger.json" "Log in"] (nav-links)))
           (is (= "/auth/login" (.getAttribute (q "a[href=\"/auth/login\"]") "href")))
           (is (nil? (todos-section)) "no todos without a login")
-          (is (= ["Tic-tac-toe" "Add this MCP server to Claude Code" "Browser tools (WebMCP)"]
-                 (mapv #(.-textContent %) (q-all "h2"))))))
+          (is (= ["Games" "AI setup"] (tab-titles)) "no Todos tab without a login")
+          (is (= ["Tic-tac-toe" "Calculator"] (mapv #(.-textContent %) (q-all "h2"))) "the first page is Games")))
       done)))
 
 (deftest login-state-error-test
@@ -206,6 +214,7 @@
   (async done
     (reset! rf-db/app-db (-> db/default-db
                              (assoc :user {:status :logged-in :login "alice"})
+                             (assoc :page :todos)
                              (assoc-in [:todos :status] :loading)))
     (tu/finish
       (steps
@@ -308,7 +317,9 @@
           (is (empty? (filter #(= "gold" (.. % -style -background)) (q-all "section button[aria-label^=Cell]"))))))
       done)))
 
-;; --- The setup sections ---
+;; --- The AI setup page ---
+
+(defn- open-ai-setup! [] (open-page! :ai-setup))
 
 (defn- with-clipboard
   "Runs `f` with navigator.clipboard set to `clipboard`, and takes it away afterwards."
@@ -321,16 +332,15 @@
   (async done
     (tu/finish
       (steps
-        open-page!
-        #(tu/eventually (fn [] (q "details")))
+        open-ai-setup!
+        #(tu/eventually (fn [] (q "section pre")))
         (fn []
-          (let [details (first (q-all "details"))]
-            (is (nil? (.getAttribute details "open")) "folded away to start with")
-            (is (= "Add this MCP server to Claude Code" (text "details summary")))
-            (is (= "claude mcp add --transport http tbd http://localhost:3000/mcp" (text "details pre code"))
+          (let [section (first (q-all "section"))]
+            (is (= "Add this MCP server to Claude Code" (text "section h2")))
+            (is (= "claude mcp add --transport http tbd http://localhost:3000/mcp" (text "section pre code"))
                 "the command names the address the page was loaded from")
             (is (= ["claude" "/mcp" "tbd"]
-                   (mapv #(.-textContent %) (.querySelectorAll details "ol code")))))))
+                   (mapv #(.-textContent %) (.querySelectorAll section "ol code")))))))
       done)))
 
 (deftest mcp-no-copy-button-without-clipboard-test
@@ -338,10 +348,10 @@
   (async done
     (tu/finish
       (steps
-        open-page!
-        #(tu/eventually (fn [] (q "details")))
+        open-ai-setup!
+        #(tu/eventually (fn [] (q "section pre")))
         (fn []
-          (is (nil? (q "details pre + button")))))
+          (is (nil? (q "section pre + button")))))
       done)))
 
 (deftest mcp-copy-button-test
@@ -352,30 +362,108 @@
           #js {:writeText (fn [s] (swap! copied conj s) (js/Promise.resolve))}
           (fn []
             (steps
-              open-page!
-              #(tu/eventually (fn [] (q "details pre + button")))
+              open-ai-setup!
+              #(tu/eventually (fn [] (q "section pre + button")))
               (fn []
-                (is (= "Copy" (text "details pre + button")))
-                (click! (q "details pre + button")))
-              #(shows "the button says so" "details pre + button" "Copied")
+                (is (= "Copy" (text "section pre + button")))
+                (click! (q "section pre + button")))
+              #(shows "the button says so" "section pre + button" "Copied")
               (fn []
                 (is (= ["claude mcp add --transport http tbd http://localhost:3000/mcp"] @copied))
                 ;; The 2 seconds are up.
                 (rf/dispatch-sync [::events/mcp-copied-timeout]))
-              #(shows "the button is back" "details pre + button" "Copy"))))
+              #(shows "the button is back" "section pre + button" "Copy"))))
         done))))
 
 (deftest browser-tools-test
   (async done
     (tu/finish
       (steps
-        open-page!
-        #(tu/eventually (fn [] (second (q-all "details"))))
+        open-ai-setup!
+        #(tu/eventually (fn [] (second (q-all "section"))))
         (fn []
-          (let [section (second (q-all "details"))]
-            (is (= "Browser tools (WebMCP)" (.-textContent (.querySelector section "summary"))))
+          (let [section (second (q-all "section"))]
+            (is (= "Browser tools (WebMCP)" (.-textContent (.querySelector section "h2"))))
             (is (= (str (count webmcp/tools)) (.-textContent (.querySelector section "p strong")))
                 "it counts the tools the page really offers")
             (is (= "https://webmcp.dev" (.getAttribute (.querySelector section "p a") "href")))
             (is (= 4 (.-length (.querySelectorAll section "ol li")))))))
       done)))
+
+;; --- The tabs ---
+
+(defn- current-tab []
+  (some-> (q "nav a[aria-current=page]") .-textContent))
+
+(deftest tabs-test
+  (async done
+    (tu/finish
+      (steps
+        open-page!
+        #(tu/eventually (fn [] (q "nav a")))
+        (fn []
+          (is (= "Games" (current-tab)) "it starts on the first tab")
+          (is (= "#/games" (.getAttribute (q "nav a") "href")))
+          (is (some? (q "[role=status]")) "the game is on the page")
+          (is (nil? (q "details")) "nothing is folded away")
+          (click! (second (q-all "nav a"))))
+        #(tu/eventually (fn [] (= "AI setup" (current-tab))))
+        (fn []
+          (is (= "#/ai-setup" js/location.hash) "a page has an address of its own")
+          (is (nil? (q "[role=status]")) "the game is gone")
+          (is (= ["Add this MCP server to Claude Code" "Browser tools (WebMCP)"]
+                 (mapv #(.-textContent %) (q-all "h2"))))
+          ;; Back.
+          (set! js/location.hash "#/games"))
+        #(tu/eventually (fn [] (= "Games" (current-tab))))
+        (fn [shown]
+          (is shown "following the address (Back, Forward, a typed one) shows that page")
+          (is (some? (q "[role=status]")))))
+      done)))
+
+(deftest page-address-test
+  (async done
+    (tu/finish
+      (steps
+        #(open-page! :ai-setup)
+        #(tu/eventually (fn [] (q "nav a")))
+        (fn []
+          (is (= "AI setup" (current-tab)) "a page can be opened by its address")
+          (set! js/location.hash "#/nowhere"))
+        #(tu/eventually (fn [] (= "Games" (current-tab))))
+        (fn [shown]
+          (is shown "an address that names no page shows the first one")))
+      done)))
+
+(deftest todos-tab-test
+  (async done
+    (tu/finish
+      (steps
+        #(log-in-page! [])
+        (fn []
+          (is (= ["Games" "Todos" "AI setup"] (tab-titles)))
+          (is (= "Todos" (current-tab)))
+          (click! (q "nav a"))
+          (tu/eventually (fn [] (= "Games" (current-tab)))))
+        (fn [_]
+          (is (nil? (todos-section)) "the todos are on their own page")
+          (click! (second (q-all "nav a"))))
+        #(tu/eventually (fn [] (todos-section)))
+        (fn [shown]
+          (is shown "and back")))
+      done)))
+
+(deftest todos-page-without-login-test
+  ;; Its address can be opened (a bookmark) without a login: the page says why it is empty.
+  (async done
+    (tu/finish
+      (steps
+        #(open-page! :todos)
+        #(tu/eventually (fn [] (some #{"Log in"} (nav-links))))
+        (fn []
+          (is (= ["Games" "AI setup"] (tab-titles)))
+          (is (nil? (todos-section)))
+          (is (= "Todos" (text "section h2")))
+          (is (= "Log in" (text "section p a")))
+          (is (= "/auth/login" (.getAttribute (q "section p a") "href")))))
+      done)))

ui/test/tbd/ui/webmcp_test.cljs

@@ -20,6 +20,7 @@
                                                      :execute execute}))})
 
 (use-fixtures :each
+  tu/url-fixture
   {:before (fn []
              (reset! registered {})
              ((:before tu/fake-server-fixture)))
@@ -147,6 +148,59 @@
                  (is (empty? (:todos @tu/server)) "nothing was sent")
                  (done))))))
 
+;; A tool that acts on the page opens the page it acts on, as a click on its tab would.
+
+(defn- page [] (:page @rf-db/app-db))
+
+(deftest tools-open-the-page-they-act-on
+  (tu/log-in!)
+  (swap! tu/server assoc :todos [{:id 1 :owner-id 7 :title "old" :done false :created-at 1 :updated-at 1}]
+         :next-id 2)
+  (open-page!)
+  (async done
+    (-> (page-loaded)
+        (.then (fn [_]
+                 (rf/dispatch-sync [::events/navigate :ai-setup])
+                 (call "get_tic_tac_toe" {})))
+        (.then (fn [_]
+                 (is (= :ai-setup (page)) "reading changes nothing")
+                 (call "move_tic_tac_toe" {:cell 4})))
+        (.then (fn [_]
+                 (is (= :games (page)))
+                 (rf/dispatch-sync [::events/navigate :ai-setup])
+                 (call "new_tic_tac_toe_game" {})))
+        (.then (fn [_]
+                 (is (= :games (page)))
+                 (rf/dispatch-sync [::events/navigate :ai-setup])
+                 (call "add" {:x 1 :y 2})))
+        (.then (fn [_]
+                 (is (= :games (page)) "the calculator is on the games page")
+                 (call "list_todos" {})))
+        (.then (fn [_]
+                 (is (= :games (page)))
+                 (call "create_todo" {:title "buy milk"})))
+        (.then (fn [_]
+                 (is (= :todos (page)))
+                 (rf/dispatch-sync [::events/navigate :games])
+                 (call "set_todo_done" {:id 1 :done true})))
+        (.then (fn [_]
+                 (is (= :todos (page)))
+                 (rf/dispatch-sync [::events/navigate :games])
+                 (call "delete_todo" {:id 1})))
+        (.then (fn [_]
+                 (is (= :todos (page)))
+                 (done))))))
+
+(deftest a-tool-that-fails-leaves-the-page-alone
+  (open-page!)
+  (async done
+    (-> (page-loaded)
+        (.then (fn [_] (call "create_todo" {:title "buy milk"})))
+        (.then (fn [r]
+                 (is (:error? r) "not logged in")
+                 (is (= :games (page)) "so there is no todos page to go to")
+                 (done))))))
+
 (deftest todos
   (tu/log-in!)
   (swap! tu/server assoc :todos [{:id 1 :owner-id 7 :title "old" :done false :created-at 1 :updated-at 1}]