VIA-172 AS Add test for generate-refresh-client-assertion

Author: anoop-surej-nhs

src/utils/auth/generate-refresh-client-assertion.test.ts

@@ -0,0 +1,78 @@
+/**
+ * @jest-environment node
+ */
+
+import { generateClientAssertion } from "@src/utils/auth/generate-refresh-client-assertion";
+import pemToCryptoKey from "@src/utils/auth/pem-to-crypto-key";
+import { AppConfig } from "@src/utils/config";
+
+jest.mock("@src/utils/auth/pem-to-crypto-key");
+
+const mockConfig = {
+  NHS_LOGIN_PRIVATE_KEY: "mock-private-key",
+  NHS_LOGIN_CLIENT_ID: "mock-client-id",
+  NHS_LOGIN_URL: "https://mock.nhs.login",
+} as AppConfig;
+
+describe("generateClientAssertion", () => {
+  let randomUUIDSpy: jest.SpyInstance;
+  let subtleSignSpy: jest.SpyInstance;
+
+  beforeAll(() => {
+    randomUUIDSpy = jest
+      .spyOn(global.crypto, "randomUUID")
+      .mockReturnValue("mock-jti");
+    subtleSignSpy = jest
+      .spyOn(global.crypto.subtle, "sign")
+      .mockResolvedValue(new Uint8Array([1, 2, 3, 4]).buffer);
+  });
+
+  beforeEach(() => {
+    // Reset mocks before each test
+    (pemToCryptoKey as jest.Mock).mockReset();
+    randomUUIDSpy.mockClear();
+    subtleSignSpy.mockClear();
+  });
+
+  afterAll(() => {
+    // Restore original implementations after all tests in this describe block
+    randomUUIDSpy.mockRestore();
+    subtleSignSpy.mockRestore();
+  });
+
+  it("should generate a client assertion JWT string", async () => {
+    (pemToCryptoKey as jest.Mock).mockResolvedValue({} as CryptoKey);
+
+    const token = await generateClientAssertion(mockConfig);
+
+    expect(typeof token).toBe("string");
+    const parts = token.split(".");
+    expect(parts.length).toBe(3);
+
+    expect(pemToCryptoKey).toHaveBeenCalledWith(
+      mockConfig.NHS_LOGIN_PRIVATE_KEY,
+    );
+
+    expect(global.crypto.randomUUID).toHaveBeenCalled();
+
+    expect(global.crypto.subtle.sign).toHaveBeenCalledWith(
+      { name: "RSASSA-PKCS1-v1_5", hash: "SHA-512" },
+      expect.anything(), // privateKey
+      expect.any(Uint8Array),
+    );
+  });
+
+  it("should throw if pemToCryptoKey rejects", async () => {
+    (pemToCryptoKey as jest.Mock).mockRejectedValue(new Error("Invalid key"));
+
+    await expect(generateClientAssertion(mockConfig)).rejects.toThrow(
+      "Invalid key",
+    );
+
+    expect(pemToCryptoKey).toHaveBeenCalledWith(
+      mockConfig.NHS_LOGIN_PRIVATE_KEY,
+    );
+    expect(global.crypto.randomUUID).not.toHaveBeenCalled();
+    expect(global.crypto.subtle.sign).not.toHaveBeenCalled();
+  });
+});