added isJWKMetadata test

Author: Code-Hex

src/jwk-fetcher.ts

@@ -10,7 +10,7 @@ interface JWKMetadata {
   keys: Array<JsonWebKeyWithKid>;
 }
 
-const isJWKMetadata = (value: any): value is JWKMetadata =>
+export const isJWKMetadata = (value: any): value is JWKMetadata => 
   isNonNullObject(value) && !!value.keys && isArray(value.keys);
 
 /**

tests/jwk-fetcher.test.ts

@@ -1,7 +1,7 @@
 import { Miniflare } from 'miniflare';
 import { describe, it, expect, vi } from 'vitest';
 import type { Fetcher } from '../src/jwk-fetcher';
-import { parseMaxAge, UrlKeyFetcher } from '../src/jwk-fetcher';
+import { isJWKMetadata, parseMaxAge, UrlKeyFetcher } from '../src/jwk-fetcher';
 import { WorkersKVStore } from '../src/key-store';
 
 class HTTPMockFetcher implements Fetcher {
@@ -158,3 +158,38 @@ describe('parseMaxAge', () => {
     expect(maxAge).toStrictEqual(want);
   });
 });
+
+describe('isJWKMetadata', () => {
+  it('should return true for valid JWKMetadata', () => {
+    const valid = JSON.parse(validResponseJSON)
+    expect(isJWKMetadata(valid)).toBe(true);
+  });
+
+  it('should return false for null', () => {
+    expect(isJWKMetadata(null)).toBe(false);
+  });
+
+  it('should return false for undefined', () => {
+    expect(isJWKMetadata(undefined)).toBe(false);
+  });
+
+  it('should return false for non-object', () => {
+    expect(isJWKMetadata('string')).toBe(false);
+    expect(isJWKMetadata(123)).toBe(false);
+    expect(isJWKMetadata(true)).toBe(false);
+  });
+
+  it('should return false for object without keys property', () => {
+    const invalidJWKMetadata = {
+      notKeys: [],
+    };
+    expect(isJWKMetadata(invalidJWKMetadata)).toBe(false);
+  });
+
+  it('should return false for object with non-array keys property', () => {
+    const invalidJWKMetadata = {
+      keys: 'notArray',
+    };
+    expect(isJWKMetadata(invalidJWKMetadata)).toBe(false);
+  });
+});