feat: write tests for useCountdown

react-app/src/hooks/useCountdown/index.test.ts

@@ -0,0 +1,77 @@
+import { act, renderHook } from "@testing-library/react";
+import { beforeEach, describe, expect, test, vi } from "vitest";
+import { useCountdown } from ".";
+
+const COUNTDOWN_TIME = 10;
+
+describe("useCountdown", () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+  });
+
+  test("Returns the correct initial value", () => {
+    const { result } = renderHook(() => useCountdown(COUNTDOWN_TIME));
+
+    expect(result.current[0]).toBe(COUNTDOWN_TIME);
+  });
+
+  test("Returns 0 after counting down", () => {
+    const { result } = renderHook(() => useCountdown(COUNTDOWN_TIME));
+
+    act(result.current[1].startCountdown);
+
+    act(() => {
+      vi.advanceTimersByTime(COUNTDOWN_TIME * 1000);
+    });
+
+    expect(result.current[0]).toBe(0);
+  });
+
+  test("Correctly starts the countdown", () => {
+    const { result } = renderHook(() => useCountdown(COUNTDOWN_TIME));
+
+    act(result.current[1].startCountdown);
+
+    act(() => {
+      vi.advanceTimersByTime(5 * 1000);
+    });
+
+    expect(result.current[0]).toBe(COUNTDOWN_TIME - 5);
+  });
+
+  test("Correctly stops the countdown", () => {
+    const { result } = renderHook(() => useCountdown(COUNTDOWN_TIME));
+
+    act(result.current[1].startCountdown);
+
+    act(() => {
+      vi.advanceTimersByTime(5 * 1000);
+    });
+
+    act(result.current[1].stopCountdown);
+
+    act(() => {
+      vi.advanceTimersByTime(5 * 1000);
+    });
+
+    expect(result.current[0]).toBe(COUNTDOWN_TIME - 5);
+  });
+
+  test("Correctly resets the countdown", () => {
+    const { result } = renderHook(() => useCountdown(COUNTDOWN_TIME));
+
+    act(result.current[1].startCountdown);
+
+    act(() => {
+      vi.advanceTimersByTime(5 * 1000);
+    });
+
+    act(result.current[1].resetCountdown);
+
+    act(() => {
+      vi.advanceTimersByTime(5 * 1000);
+    });
+
+    expect(result.current[0]).toBe(COUNTDOWN_TIME);
+  });
+});