[HOTE-871] fix: prevent revisiting check-your-answers via browser back

ui/src/__tests__/components/FormBackLink.test.tsx

@@ -1,5 +1,4 @@
 import "@testing-library/jest-dom";
-
 import { fireEvent, render, screen } from "@testing-library/react";
 
 import { FormBackLink } from "@/components/FormBackLink";
@@ -12,6 +11,9 @@ const mockNavigationContext = {
   goBack: jest.fn(),
   canGoBack: jest.fn(() => true),
   clearHistory: jest.fn(),
+  resetNavigation: jest.fn(),
+  returnToStep: null,
+  setReturnToStep: jest.fn(),
 };
 
 jest.mock("@/state", () => ({
@@ -109,7 +111,7 @@ describe("FormBackLink", () => {
 
       // BackLink should still be rendered but with empty text
       // Check for the back link container class
-      expect(document.querySelector('.nhsuk-back-link')).toBeInTheDocument();
+      expect(document.querySelector(".nhsuk-back-link")).toBeInTheDocument();
     });
   });
 

ui/src/__tests__/routes/get-self-test-kit-for-HIV-journey/CannotUseServiceUnder18Page.test.tsx

@@ -46,6 +46,7 @@ jest.mock("@/hooks", () => ({
 
 const goBackMock = jest.fn();
 const goToStepMock = jest.fn();
+const resetNavigationMock = jest.fn();
 
 const TestProvider = ({
   children,
@@ -77,6 +78,7 @@ const TestProvider = ({
           goToStep: goToStepMock,
           canGoBack: () => history.length > 1,
           clearHistory: jest.fn(),
+          resetNavigation: resetNavigationMock,
           setReturnToStep: jest.fn(),
         }}
       >

ui/src/__tests__/routes/get-self-test-kit-for-HIV-journey/CheckYourAnswersPage.test.tsx

@@ -1,21 +1,37 @@
+import { fireEvent, render, screen, waitFor } from "@testing-library/react";
+import { useEffect } from "react";
+import { MemoryRouter } from "react-router-dom";
+
+import { RoutePath } from "@/lib/models/route-paths";
+import orderService from "@/lib/services/order-service";
 import { TestErrorBoundary } from "@/lib/test-utils/TestErrorBoundary";
+import CheckYourAnswersPage from "@/routes/get-self-test-kit-for-HIV-journey/CheckYourAnswersPage";
 import {
   AuthProvider,
   AuthUser,
   CreateOrderProvider,
   useAuth,
   useCreateOrderContext,
 } from "@/state";
-import { fireEvent, render, screen, waitFor } from "@testing-library/react";
 
-import CheckYourAnswersPage from "@/routes/get-self-test-kit-for-HIV-journey/CheckYourAnswersPage";
-import { MemoryRouter } from "react-router-dom";
-import orderService from "@/lib/services/order-service";
-import { useEffect } from "react";
+const mockNavigate = jest.fn();
+const mockClearAddresses = jest.fn();
+let mockNavigationType = "PUSH";
+
+jest.mock("react-router-dom", () => {
+  const actual = jest.requireActual("react-router-dom");
+
+  return {
+    ...actual,
+    useNavigate: () => mockNavigate,
+    useNavigationType: () => mockNavigationType,
+  };
+});
 
 const mockGoToStep = jest.fn();
 const mockSetReturnToStep = jest.fn();
 const mockGoBack = jest.fn();
+const mockResetNavigation = jest.fn();
 
 jest.mock("@/state", () => {
   const actual = jest.requireActual("@/state");
@@ -29,8 +45,20 @@ jest.mock("@/state", () => {
       goBack: mockGoBack,
       canGoBack: () => true,
       clearHistory: jest.fn(),
+      resetNavigation: mockResetNavigation,
       setReturnToStep: mockSetReturnToStep,
     }),
+    usePostcodeLookup: () => ({
+      postcode: "",
+      addresses: [],
+      selectedAddress: null,
+      isLoading: false,
+      lookupResultsStatus: "idle",
+      error: null,
+      lookupPostcode: jest.fn(),
+      setSelectedAddress: jest.fn(),
+      clearAddresses: mockClearAddresses,
+    }),
   };
 });
 
@@ -79,10 +107,10 @@ function StateSeeder({
 function AuthSeeder({
   children,
   user = defaultAuthUser,
-}: {
+}: Readonly<{
   children: React.ReactNode;
   user?: AuthUser;
-}) {
+}>) {
   const { setUser } = useAuth();
 
   useEffect(() => {
@@ -139,6 +167,7 @@ describe("CheckYourAnswersPage", () => {
 
   beforeEach(() => {
     jest.clearAllMocks();
+    mockNavigationType = "PUSH";
   });
 
   describe("Component Rendering", () => {
@@ -308,6 +337,36 @@ describe("CheckYourAnswersPage", () => {
   });
 
   describe("Submit Order", () => {
+    it("clears state and redirects to start when revisited via browser back after submission", async () => {
+      mockNavigationType = "POP";
+
+      render(
+        <>
+          <CheckYourAnswersPage />
+          <OrderReferenceObserver />
+        </>,
+        {
+          wrapper: (props) => (
+            <TestWrapper
+              orderData={{
+                ...defaultOrderData,
+                orderReferenceNumber: 123,
+              }}
+              {...props}
+            />
+          ),
+        },
+      );
+
+      await waitFor(() => {
+        expect(mockClearAddresses).toHaveBeenCalled();
+        expect(mockResetNavigation).toHaveBeenCalledWith(RoutePath.GetSelfTestKitPage, {
+          replace: true,
+        });
+        expect(screen.getByTestId("order-reference")).toHaveTextContent("");
+      });
+    });
+
     it("shows error when submitting without consent", async () => {
       render(<CheckYourAnswersPage />, { wrapper: TestWrapper });
 

ui/src/__tests__/routes/get-self-test-kit-for-HIV-journey/OrderSubmittedPage.test.tsx

@@ -1,13 +1,14 @@
-import { CreateOrderProvider, JourneyNavigationProvider, useCreateOrderContext } from "@/state";
 import { render, screen } from "@testing-library/react";
-
+import { useEffect } from "react";
 import { MemoryRouter } from "react-router-dom";
+
 import OrderSubmittedPage from "@/routes/get-self-test-kit-for-HIV-journey/OrderSubmittedPage";
-import { useEffect } from "react";
+import { CreateOrderProvider, JourneyNavigationProvider, useCreateOrderContext } from "@/state";
 
 const mockGoToStep = jest.fn();
 const mockSetReturnToStep = jest.fn();
 const mockGoBack = jest.fn();
+const mockResetNavigation = jest.fn();
 
 jest.mock("@/state", () => {
   const actual = jest.requireActual("@/state");
@@ -21,6 +22,7 @@ jest.mock("@/state", () => {
       goBack: mockGoBack,
       canGoBack: () => false,
       clearHistory: jest.fn(),
+      resetNavigation: mockResetNavigation,
       setReturnToStep: mockSetReturnToStep,
     }),
   };

ui/src/__tests__/routes/get-self-test-kit-for-HIV-journey/SelectDeliveryAddressPage.test.tsx

@@ -1,4 +1,11 @@
 import "@testing-library/jest-dom";
+import { fireEvent, render, screen, waitFor } from "@testing-library/react";
+import { useEffect } from "react";
+import { MemoryRouter } from "react-router-dom";
+
+import { JourneyStepNames } from "@/lib/models/route-paths";
+import laLookupService from "@/lib/services/la-lookup-service";
+import SelectDeliveryAddressPage from "@/routes/get-self-test-kit-for-HIV-journey/SelectDeliveryAddressPage";
 import {
   AuthContext,
   AuthUser,
@@ -7,12 +14,6 @@ import {
   PostcodeLookupProvider,
   useCreateOrderContext,
 } from "@/state";
-import { fireEvent, render, screen, waitFor } from "@testing-library/react";
-import { JourneyStepNames } from "@/lib/models/route-paths";
-import { MemoryRouter } from "react-router-dom";
-import SelectDeliveryAddressPage from "@/routes/get-self-test-kit-for-HIV-journey/SelectDeliveryAddressPage";
-import laLookupService from "@/lib/services/la-lookup-service";
-import { useEffect } from "react";
 
 const FIXED_TODAY = new Date(2026, 2, 4); // March 4, 2026
 
@@ -26,6 +27,7 @@ const mockNavigationContext: {
   goBack: jest.Mock;
   canGoBack: jest.Mock;
   clearHistory: jest.Mock;
+  resetNavigation: jest.Mock;
   stepHistory: string[];
   returnToStep: string | null;
   setReturnToStep: jest.Mock;
@@ -35,6 +37,7 @@ const mockNavigationContext: {
   goBack: jest.fn(),
   canGoBack: jest.fn(() => true),
   clearHistory: jest.fn(),
+  resetNavigation: jest.fn(),
   stepHistory: ["enter-delivery-address", "select-delivery-address"],
   returnToStep: null,
   setReturnToStep: jest.fn(),

ui/src/__tests__/state/NavigationContext.test.tsx

@@ -0,0 +1,91 @@
+import "@testing-library/jest-dom";
+import { act, renderHook, waitFor } from "@testing-library/react";
+import { MemoryRouter } from "react-router-dom";
+
+import { JourneyStepNames, RoutePath } from "@/lib/models/route-paths";
+import { SESSION_STORAGE_KEYS } from "@/lib/services/session-service";
+import { JourneyNavigationProvider, useJourneyNavigationContext } from "@/state/NavigationContext";
+
+function TestWrapper({ children }: Readonly<{ children: React.ReactNode }>) {
+  return (
+    <MemoryRouter
+      initialEntries={[`${RoutePath.GetSelfTestKitPage}/${JourneyStepNames.CheckYourAnswers}`]}
+    >
+      <JourneyNavigationProvider>{children}</JourneyNavigationProvider>
+    </MemoryRouter>
+  );
+}
+
+describe("NavigationContext", () => {
+  beforeEach(() => {
+    globalThis.sessionStorage.clear();
+  });
+
+  describe("JourneyNavigationProvider", () => {
+    it("provides the current step as the initial history", () => {
+      const { result } = renderHook(() => useJourneyNavigationContext(), {
+        wrapper: TestWrapper,
+      });
+
+      expect(result.current.currentStep).toBe(JourneyStepNames.CheckYourAnswers);
+      expect(result.current.stepHistory).toEqual([JourneyStepNames.CheckYourAnswers]);
+      expect(result.current.returnToStep).toBeNull();
+    });
+
+    it("rehydrates persisted navigation and appends the current step when needed", () => {
+      globalThis.sessionStorage.setItem(
+        SESSION_STORAGE_KEYS.journeyNavigation,
+        JSON.stringify({
+          stepHistory: [JourneyStepNames.EnterMobileNumber],
+          returnToStep: JourneyStepNames.CheckYourAnswers,
+        }),
+      );
+
+      const { result } = renderHook(() => useJourneyNavigationContext(), {
+        wrapper: TestWrapper,
+      });
+
+      expect(result.current.stepHistory).toEqual([
+        JourneyStepNames.EnterMobileNumber,
+        JourneyStepNames.CheckYourAnswers,
+      ]);
+      expect(result.current.returnToStep).toBe(JourneyStepNames.CheckYourAnswers);
+    });
+
+    it("resetNavigation clears in-memory navigation and storage for a redirect target", async () => {
+      const { result } = renderHook(() => useJourneyNavigationContext(), {
+        wrapper: TestWrapper,
+      });
+
+      act(() => {
+        result.current.setReturnToStep(JourneyStepNames.CheckYourAnswers);
+      });
+
+      await waitFor(() => {
+        expect(
+          globalThis.sessionStorage.getItem(SESSION_STORAGE_KEYS.journeyNavigation),
+        ).not.toBeNull();
+      });
+
+      act(() => {
+        result.current.resetNavigation(RoutePath.GetSelfTestKitPage);
+      });
+
+      await waitFor(() => {
+        expect(result.current.currentStep).toBe(RoutePath.GetSelfTestKitPage);
+      });
+
+      expect(result.current.returnToStep).toBeNull();
+      expect(result.current.stepHistory).toEqual([RoutePath.GetSelfTestKitPage]);
+      expect(globalThis.sessionStorage.getItem(SESSION_STORAGE_KEYS.journeyNavigation)).toBeNull();
+    });
+  });
+
+  describe("useJourneyNavigationContext", () => {
+    it("throws when used outside provider", () => {
+      expect(() => {
+        renderHook(() => useJourneyNavigationContext());
+      }).toThrow("useJourneyNavigationContext must be used within a JourneyNavigationProvider");
+    });
+  });
+});

ui/src/app.tsx

@@ -1,12 +1,11 @@
 import * as React from "react";
-import { RouterProvider, createBrowserRouter } from "react-router-dom";
+import { Navigate, RouterProvider, createBrowserRouter } from "react-router-dom";
 
 import ErrorRedirect from "./components/ErrorRedirect";
 import JourneyLayout from "./layouts/JourneyLayout";
 import MainLayout from "./layouts/MainLayout";
 import { JourneyStepNames, RoutePath } from "./lib/models/route-paths";
 import CallbackPage from "./routes/CallbackPage";
-import HomePage from "./routes/HomePage";
 import HomeTestPrivacyPolicyPage from "./routes/HomeTestPrivacyPolicyPage";
 import HomeTestTermsOfUsePage from "./routes/HomeTestTermsOfUsePage";
 import LoginPage from "./routes/LoginPage";
@@ -75,7 +74,7 @@ const router = createBrowserRouter([
     children: [
       {
         path: RoutePath.HomePage,
-        element: <HomePage />,
+        element: <Navigate to={RoutePath.GetSelfTestKitPage} replace />,
       },
       {
         path: RoutePath.OrderTrackingPage,