diff --git a/test/build/deferred.spec.ts b/test/build/deferred.spec.ts
new file mode 100644
index 0000000..dee0270
--- /dev/null
+++ b/test/build/deferred.spec.ts
@@ -0,0 +1,8 @@
+import { describe, expect, it } from "vitest";
+import { deferred } from '../../dist/index.js'
+
+describe("deferred", () => {
+  it("must be a function", () => {
+    expect(typeof deferred).toBe("function");
+  });
+});
\ No newline at end of file
diff --git a/test/src/deferred.spec.ts b/test/src/deferred.spec.ts
new file mode 100644
index 0000000..f537dce
--- /dev/null
+++ b/test/src/deferred.spec.ts
@@ -0,0 +1,29 @@
+import { describe, expect, it } from "vitest";
+import { deferred } from '../../src/deferred.js'
+
+describe('deferred', () => {
+  it('should be a function', () => {
+    expect(typeof deferred).toBe('function')
+  })
+
+  it('should return an object', () => {
+    const deferredObject = deferred()
+    expect(deferredObject.promise instanceof Promise).toBe(true)
+    expect(deferredObject.resolve instanceof Function).toBe(true)
+    expect(deferredObject.reject instanceof Function).toBe(true)
+  })
+
+  it('should resolve the promise after calling resolve', async () => {
+    const { promise, resolve } = deferred<string>()
+    setTimeout(() => resolve('test'), 10)
+
+    expect(await promise).toBe('test')
+  })
+
+  it('should reject the promise after calling reject', async () => {
+    const { promise, reject } = deferred<string>()
+    setTimeout(() => reject('test'), 10)
+
+    await expect(promise).rejects.toBe('test')
+  })
+})
\ No newline at end of file