Set up unit testing infrastructure

Extract slot generation from book.ts into pure utility for unit testing.
Add 8 API unit tests and 4 web component tests with coverage thresholds.

Closes #39

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/src/__tests__/App.test.tsx

@@ -0,0 +1,58 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen, within, act } from "@testing-library/react";
+import { MemoryRouter } from "react-router-dom";
+import { App } from "../App.js";
+
+// Prevent fetch errors from page components loading data on mount
+beforeEach(() => {
+  global.fetch = vi.fn().mockResolvedValue({
+    ok: true,
+    json: async () => [],
+  } as unknown as Response);
+});
+
+async function renderApp(route = "/") {
+  await act(async () => {
+    render(
+      <MemoryRouter initialEntries={[route]}>
+        <App />
+      </MemoryRouter>
+    );
+  });
+  return screen.getByRole("navigation");
+}
+
+describe("App navigation", () => {
+  it("renders the Groom Book brand", async () => {
+    const nav = await renderApp();
+    expect(within(nav).getByText("Groom Book")).toBeInTheDocument();
+  });
+
+  it("renders the Book CTA button", async () => {
+    const nav = await renderApp();
+    expect(within(nav).getByText("Book")).toBeInTheDocument();
+  });
+
+  it("renders all primary nav links", async () => {
+    const nav = await renderApp();
+    const expectedLinks = [
+      "Appointments",
+      "Clients",
+      "Services",
+      "Staff",
+      "Invoices",
+      "Group Bookings",
+      "Reports",
+    ];
+    expectedLinks.forEach((label) => {
+      expect(within(nav).getByText(label)).toBeInTheDocument();
+    });
+  });
+
+  it("highlights the active route link", async () => {
+    const nav = await renderApp("/clients");
+    const clientsLink = within(nav).getByText("Clients");
+    // Active links use fontWeight 600
+    expect(clientsLink).toHaveStyle({ fontWeight: "600" });
+  });
+});

apps/web/src/test/setup.ts

@@ -0,0 +1 @@
+import "@testing-library/jest-dom";