Add some auth tests

src/__tests__/pages/auth/signin.test.jsx

@@ -0,0 +1,72 @@
+// @vitest-environment jsdom
+
+import { render, screen, waitFor } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+
+const { getSettingsMock } = vi.hoisted(() => ({
+  getSettingsMock: vi.fn(),
+}));
+
+vi.mock("utils/config/config", () => ({
+  getSettings: getSettingsMock,
+}));
+
+import { getProviders } from "next-auth/react";
+import SignInPage, { getServerSideProps } from "pages/auth/signin";
+
+describe("pages/auth/signin", () => {
+  it("renders an error state when no providers are configured", async () => {
+    render(
+      <SignInPage
+        providers={{}}
+        settings={{
+          theme: "dark",
+          color: "slate",
+          title: "Homepage",
+        }}
+      />,
+    );
+
+    expect(screen.getByText("Authentication not configured")).toBeInTheDocument();
+
+    await waitFor(() => {
+      expect(document.documentElement.classList.contains("dark")).toBe(true);
+      expect(document.documentElement.classList.contains("scheme-dark")).toBe(true);
+      expect(document.documentElement.classList.contains("theme-slate")).toBe(true);
+    });
+  });
+
+  it("renders provider buttons when providers are available", () => {
+    render(
+      <SignInPage
+        providers={{
+          oidc: { id: "oidc", name: "OIDC" },
+        }}
+        settings={{
+          theme: "light",
+          color: "emerald",
+          title: "My Dashboard",
+        }}
+      />,
+    );
+
+    expect(screen.getByText("Sign in")).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: /login via oidc/i })).toBeInTheDocument();
+  });
+
+  it("getServerSideProps returns providers and settings", async () => {
+    getProviders.mockResolvedValueOnce({ foo: { id: "foo", name: "Foo" } });
+    getSettingsMock.mockReturnValueOnce({ theme: "dark" });
+
+    const res = await getServerSideProps({});
+
+    expect(getProviders).toHaveBeenCalled();
+    expect(getSettingsMock).toHaveBeenCalled();
+    expect(res).toEqual({
+      props: {
+        providers: { foo: { id: "foo", name: "Foo" } },
+        settings: { theme: "dark" },
+      },
+    });
+  });
+});