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@std/testing

Overview Jump to heading

This package provides utilities for testing.

import { assertSpyCalls, spy } from "@std/testing/mock";
import { FakeTime } from "@std/testing/time";

function secondInterval(cb: () => void): number {
  return setInterval(cb, 1000);
}

Deno.test("secondInterval calls callback every second and stops after being cleared", () => {
  using time = new FakeTime();

  const cb = spy();
  const intervalId = secondInterval(cb);
  assertSpyCalls(cb, 0);
  time.tick(500);
  assertSpyCalls(cb, 0);
  time.tick(500);
  assertSpyCalls(cb, 1);
  time.tick(3500);
  assertSpyCalls(cb, 4);

  clearInterval(intervalId);
  time.tick(1000);
  assertSpyCalls(cb, 4);
});

Add to your project Jump to heading

deno add jsr:@std/testing

See all symbols in @std/testing on

测试 Jump to heading

测试是一种验证代码行为符合预期的实践。它帮助及早发现错误，确保代码质量，并在进行修改时提供信心。

查看Deno 测试示例了解实际用法。

为什么使用 @std/testing Jump to heading

结合 Deno 内置的 Deno.test，使用这些工具编写更清晰的规范，模拟依赖，伪造定时器，创建快照。

示例 Jump to heading

import { afterEach, beforeEach, describe, it } from "@std/testing/bdd";
import { assertSpyCalls, spy } from "@std/testing/mock";
import { FakeTime } from "@std/testing/time";

describe("interval", () => {
  let time: FakeTime;
  beforeEach(() => (time = new FakeTime()));
  afterEach(() => time.restore());

  it("ticks", () => {
    const cb = spy();
    const id = setInterval(cb, 1000);
    time.tick(3000);
    assertSpyCalls(cb, 3);
    clearInterval(id);
  });
});

快照测试 Jump to heading

import { assertSnapshot } from "@std/testing/snapshot";

Deno.test("user json snapshot", async (t) => {
  const user = { id: 1, name: "Ada", tags: ["admin", "ops"] };
  await assertSnapshot(t, user);
});

Stub 全局方法 Jump to heading

import { stub } from "@std/testing/mock";
import { assertEquals } from "@std/assert";

Deno.test("stub Math.random", () => {
  const s = stub(Math, "random", () => 0.5);
  try {
    assertEquals(Math.random(), 0.5);
  } finally {
    s.restore();
  }
});

使用 returnsNext 编排序列 Jump to heading

import { returnsNext } from "@std/testing/mock";
import { assertEquals, assertThrows } from "@std/assert";

Deno.test("returnsNext sequences values and errors", () => {
  const next = returnsNext([1, 2, new Error("boom"), 3]);
  assertEquals(next(), 1);
  assertEquals(next(), 2);
  assertThrows(() => next(), Error, "boom");
  assertEquals(next(), 3);
});

监听并断言调用参数 Jump to heading

import { assertSpyCallArgs, assertSpyCalls, spy } from "@std/testing/mock";

Deno.test("spy captures calls and args", () => {
  const sum = spy((a: number, b: number) => a + b);
  sum(3, 4);
  sum(5, 6);
  assertSpyCalls(sum, 2);
  assertSpyCallArgs(sum, 0, [3, 4]);
});

小贴士 Jump to heading

  • 结合 @std/assert 或 @std/expect 使用断言。
  • 使用 FakeTime 有确定性地测试定时器和 Date.now()。
  • 在 afterEach 或 finally 块中恢复 stub/spy，避免状态泄露。
  • 将快照文件提交到版本控制，以捕获意外更改。

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