test edge case

test/spec/KeyStore.ts

@@ -79,6 +79,14 @@ describe ('key store', () => {
       .toEqual (keys[1].key);
   });
 
+  it ('should reject key generation of expired keys', () => {
+    const iat = ((new Date)
+      .getTime () / 1000) - 10;
+    const duration = 5;
+    expect (() => ks.get_key (iat, duration))
+      .toThrowError ('cannot create already expired keys');
+  });
+
   afterAll (() => {
     jasmine.clock ()
       .uninstall ();