diff --git a/src/util/deferred.ts b/src/util/deferred.ts
index c530d552..3f2413d2 100644
--- a/src/util/deferred.ts
+++ b/src/util/deferred.ts
@@ -3,8 +3,8 @@ export type MaybePromise<T> = T | PromiseLike<T>;
 /**
  * Represents the completion of an asynchronous operation that can be completed later.
  */
-export class Deferred<T> implements PromiseLike<T> {
-  readonly promise: Promise<T>;
+export class Deferred<T = any> implements PromiseLike<T> {
+  private readonly promise: Promise<T>;
   private _resolve: (value: MaybePromise<T>) => void = () => {};
   private _reject: (reason?: any) => void = () => {};
 
diff --git a/test/util/deferred.test.ts b/test/util/deferred.test.ts
new file mode 100644
index 00000000..a5474d4b
--- /dev/null
+++ b/test/util/deferred.test.ts
@@ -0,0 +1,52 @@
+import { Deferred } from '../../src/util/deferred';
+
+describe('Tests cached status code', () => {
+  it('test resolve method', () => {
+    const deferred = new Deferred();
+
+    expect(deferred).resolves.toBe(1);
+    deferred.resolve(1);
+  });
+
+  it('test reject method', () => {
+    const deferred = new Deferred();
+
+    expect(deferred).rejects.toBe(1);
+    deferred.reject(1);
+  });
+
+  it('test then method', () => {
+    const deferred = new Deferred();
+
+    deferred.then((data) => {
+      expect(data).toBe(1);
+    });
+
+    deferred.resolve(1);
+  });
+
+  it('test catch method', () => {
+    const deferred = new Deferred();
+
+    deferred.catch((data) => {
+      expect(data).toBe(1);
+    });
+
+    deferred.resolve(1);
+  });
+
+  it('test finally method', () => {
+    const deferred = new Deferred<number>();
+
+    let data: number;
+    deferred.then((d) => {
+      data = d;
+    });
+
+    deferred.finally(() => {
+      expect(data).toBe(1);
+    });
+
+    deferred.resolve(1);
+  });
+});