feat: Unleash feature flags via src/lib/flags.tsx, hello-banner on home page

src/lib/flags.test.tsx

@@ -0,0 +1,93 @@
+import { render, screen } from "@testing-library/react";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+// Mock the Unleash React SDK: capture provider props, control flag state.
+const sdk = vi.hoisted(() => ({
+  on: new Set<string>(),
+  providerProps: [] as Record<string, unknown>[],
+}));
+vi.mock("@unleash/proxy-client-react", () => ({
+  FlagProvider: (props: { children: React.ReactNode }) => {
+    sdk.providerProps.push(props);
+    return props.children;
+  },
+  useFlag: (name: string) => sdk.on.has(name),
+  useVariant: () => ({ name: "disabled", enabled: false }),
+}));
+
+import { FlagsProvider, unleashConfig, useFlag } from "./flags";
+
+function Probe() {
+  return <p>{useFlag("hello-banner") ? "on" : "off"}</p>;
+}
+
+beforeEach(() => {
+  sdk.on.clear();
+  sdk.providerProps.length = 0;
+});
+
+describe("unleashConfig", () => {
+  const base = { API_BASE_URL: "/api", APP_NAME: "web" };
+  it("is null when UNLEASH_URL or token is unset", () => {
+    expect(
+      unleashConfig({ ...base, UNLEASH_URL: "", UNLEASH_FRONTEND_TOKEN: "" }),
+    ).toBeNull();
+    expect(
+      unleashConfig({
+        ...base,
+        UNLEASH_URL: "http://u",
+        UNLEASH_FRONTEND_TOKEN: "",
+      }),
+    ).toBeNull();
+  });
+  it("points at the Frontend API", () => {
+    expect(
+      unleashConfig({
+        ...base,
+        UNLEASH_URL: "http://unleash.test/",
+        UNLEASH_FRONTEND_TOKEN: "*:development.x",
+      }),
+    ).toMatchObject({
+      url: "http://unleash.test/api/frontend",
+      clientKey: "*:development.x",
+      appName: "web",
+    });
+  });
+});
+
+describe("FlagsProvider", () => {
+  it("starts the client when configured", () => {
+    window.__APP_CONFIG__ = {
+      APP_NAME: "web",
+      UNLEASH_URL: "http://unleash.test",
+      UNLEASH_FRONTEND_TOKEN: "tok",
+    };
+    sdk.on.add("hello-banner");
+    render(
+      <FlagsProvider>
+        <Probe />
+      </FlagsProvider>,
+    );
+    expect(screen.getByText("on")).toBeInTheDocument();
+    expect(sdk.providerProps[0]).toMatchObject({
+      startClient: true,
+      config: { url: "http://unleash.test/api/frontend", clientKey: "tok" },
+    });
+  });
+
+  it("stays offline when UNLEASH_URL is unset", () => {
+    window.__APP_CONFIG__ = { APP_NAME: "web" };
+    const info = vi.spyOn(console, "info").mockImplementation(() => {});
+    render(
+      <FlagsProvider>
+        <Probe />
+      </FlagsProvider>,
+    );
+    expect(screen.getByText("off")).toBeInTheDocument();
+    expect(sdk.providerProps[0]).toMatchObject({
+      startClient: false,
+      config: { disableRefresh: true, disableMetrics: true },
+    });
+    expect(info).toHaveBeenCalledTimes(1);
+  });
+});