---
id: 587d824c367417b2b2512c4f
title: 测试某个值是否在特定范围内
challengeType: 2
forumTopicId: 301598
dashedName: test-if-a-value-falls-within-a-specific-range
---

# --description--

请注意，本项目在 [这个 Repl.it 项目](https://repl.it/github/freeCodeCamp/boilerplate-mochachai) 的基础上进行开发。 你也可以从 [GitHub](https://repl.it/github/freeCodeCamp/boilerplate-mochachai) 上克隆。

```javascript
.approximately(actual, expected, delta, [message])
```

断言 `actual` 等于 `expected`，在 +/- `delta` 的范围内。

# --instructions--

在 `tests/1_unit-tests.js` 中，在 `Comparisons` 套件里标有 `#10` 的测试中，将每个 `assert` 改成 `assert.approximately`，让测试通过（结果应该返回 `true`）。

选择最小范围（第三个参数）来通过所有测试。 它应该小于 1。

# --hints--

不应有未通过的测试

```js
(getUserInput) =>
  $.get(getUserInput('url') + '/_api/get-tests?type=unit&n=9').then(
    (data) => {
      assert.equal(data.state, 'passed');
    },
    (xhr) => {
      throw new Error(xhr.responseText);
    }
  );
```

应该为第一个断言选择正确的范围——`approximately(actual, expected, range)`。

```js
(getUserInput) =>
  $.get(getUserInput('url') + '/_api/get-tests?type=unit&n=9').then(
    (data) => {
      assert.equal(data.assertions[0].method, 'approximately');
      assert.equal(
        data.assertions[0].args[2],
        0.5,
        "weirdNumbers(0.5) is in the range (0.5, 1.5]. It's within 1 +/- 0.5"
      );
    },
    (xhr) => {
      throw new Error(xhr.responseText);
    }
  );
```

应该为第二个断言选择正确的范围——`approximately(actual, expected, range)`。

```js
(getUserInput) =>
  $.get(getUserInput('url') + '/_api/get-tests?type=unit&n=9').then(
    (data) => {
      assert.equal(data.assertions[1].method, 'approximately');
      assert.equal(
        data.assertions[1].args[2],
        0.8,
        "weirdNumbers(0.2) is in the range (0.2, 1.2]. It's within 1 +/- 0.8"
      );
    },
    (xhr) => {
      throw new Error(xhr.responseText);
    }
  );
```

# --solutions--

```js
/**
  Backend challenges don't need solutions, 
  because they would need to be tested against a full working project. 
  Please check our contributing guidelines to learn more.
*/
```
