add utils tests

Author: nicknisi

src/utils.spec.ts

@@ -0,0 +1,60 @@
+import { isDataWithResponseInit, isRedirect, isResponse, lazy } from './utils.js';
+
+describe('utils', () => {
+  describe('lazy', () => {
+    it('should call the function only once', () => {
+      const fn = jest.fn(() => 'test');
+      const lazyFn = lazy(fn);
+
+      expect(fn).not.toHaveBeenCalled();
+
+      expect(lazyFn()).toBe('test');
+      expect(fn).toHaveBeenCalledTimes(1);
+
+      expect(lazyFn()).toBe('test');
+      expect(fn).toHaveBeenCalledTimes(1);
+    });
+  });
+
+  describe('isRedirect', () => {
+    it('should return true for a redirect response', () => {
+      const res = new Response(null, { status: 302 });
+
+      expect(isRedirect(res)).toBe(true);
+    });
+
+    it('should return false for a non-redirect response', () => {
+      const res = new Response(null, { status: 200 });
+
+      expect(isRedirect(res)).toBe(false);
+    });
+  });
+
+  describe('isResponse', () => {
+    it('should return true for a Response object', () => {
+      const res = new Response();
+
+      expect(isResponse(res)).toBe(true);
+    });
+
+    it('should return false for a non-Response object', () => {
+      expect(isResponse({})).toBe(false);
+    });
+  });
+
+  describe('isDataWithResponseInit', () => {
+    it('should return true for a DataWithResponseInit object', () => {
+      const data = {
+        type: 'DataWithResponseInit',
+        data: {},
+        init: {},
+      };
+
+      expect(isDataWithResponseInit(data)).toBe(true);
+    });
+
+    it('should return false for a non-DataWithResponseInit object', () => {
+      expect(isDataWithResponseInit({})).toBe(false);
+    });
+  });
+});

src/utils.ts

@@ -38,7 +38,9 @@ export function isResponse(response: unknown): response is Response {
 }
 
 /**
- * Returns true if the data is a DataWithResponseInit object.
+ * Checks if the data is a DataWithResponseInit object.
+ * @param data - The data to check.
+ * @returns True if the data is a DataWithResponseInit object.
  */
 export function isDataWithResponseInit(data: unknown): data is DataWithResponseInit<unknown> {
   return (