Avoid app crash with no cookie value

.changeset/angry-camels-tie.md

@@ -0,0 +1,5 @@
+---
+"@guardian/pan-domain-node": minor
+---
+
+Fix app crash with no cookie value

src/panda.ts

@@ -146,9 +146,9 @@ export class PanDomainAuthentication {
         });
     }
 
-    verify(requestCookies: string): Promise<AuthenticationResult> {
+    verify(requestCookies: string | undefined): Promise<AuthenticationResult> {
         return this.getPublicKey().then(publicKey => {
-            const cookies = cookie.parse(requestCookies);
+            const cookies = cookie.parse(requestCookies ?? '');
             const pandaCookie = cookies[this.cookieName];
             return verifyUser(pandaCookie, publicKey, new Date(), this.validateUser);
         });

test/panda.test.ts

@@ -349,6 +349,20 @@ describe('panda class', function () {
       };
       expect(authenticationResult).toStrictEqual(expected);
     });
+
+    it('should fail to authenticate with no-cookie reason if no cookie is present at all', async () => {
+      jest.setSystemTime(100);
+
+      const panda = new PanDomainAuthentication('rightcookiename', 'region', 'bucket', 'keyfile', guardianValidation);
+      const noCookie = undefined;
+      const authenticationResult = await panda.verify(noCookie);
+
+      const expected: CookieFailure = {
+        success: false,
+        reason: "no-cookie"
+      };
+      expect(authenticationResult).toStrictEqual(expected);
+    });
   });
 
 });