Mocking
node:test
模块支持通过顶级 mock
对象在测试期间进行模拟。
以下示例创建了一个对将两个数字相加的函数的监视。
间谍随后被用来断言该函数已按预期调用。
import assert from 'node:assert';
import { mock, test } from 'node:test';
test('spies on a function', () => {
const sum = mock.fn((a, b) => {
return a + b;
});
assert.strictEqual(sum.mock.calls.length, 0);
assert.strictEqual(sum(3, 4), 7);
assert.strictEqual(sum.mock.calls.length, 1);
const call = sum.mock.calls[0];
assert.deepStrictEqual(call.arguments, [3, 4]);
assert.strictEqual(call.result, 7);
assert.strictEqual(call.error, undefined);
// 重置全局跟踪的模拟。
mock.reset();
});
'use strict';
const assert = require('node:assert');
const { mock, test } = require('node:test');
test('spies on a function', () => {
const sum = mock.fn((a, b) => {
return a + b;
});
assert.strictEqual(sum.mock.calls.length, 0);
assert.strictEqual(sum(3, 4), 7);
assert.strictEqual(sum.mock.calls.length, 1);
const call = sum.mock.calls[0];
assert.deepStrictEqual(call.arguments, [3, 4]);
assert.strictEqual(call.result, 7);
assert.strictEqual(call.error, undefined);
// 重置全局跟踪的模拟。
mock.reset();
});
相同的模拟功能也暴露在每个测试的 TestContext
对象上。
以下示例使用 TestContext
上公开的 API 创建对象方法的侦听器。
通过测试上下文进行模拟的好处是,测试运行器将在测试完成后自动恢复所有模拟功能。
test('spies on an object method', (t) => {
const number = {
value: 5,
add(a) {
return this.value + a;
},
};
t.mock.method(number, 'add');
assert.strictEqual(number.add.mock.calls.length, 0);
assert.strictEqual(number.add(3), 8);
assert.strictEqual(number.add.mock.calls.length, 1);
const call = number.add.mock.calls[0];
assert.deepStrictEqual(call.arguments, [3]);
assert.strictEqual(call.result, 8);
assert.strictEqual(call.target, undefined);
assert.strictEqual(call.this, number);
});
The node:test
module supports mocking during testing via a top-level mock
object. The following example creates a spy on a function that adds two numbers
together. The spy is then used to assert that the function was called as
expected.
import assert from 'node:assert';
import { mock, test } from 'node:test';
test('spies on a function', () => {
const sum = mock.fn((a, b) => {
return a + b;
});
assert.strictEqual(sum.mock.calls.length, 0);
assert.strictEqual(sum(3, 4), 7);
assert.strictEqual(sum.mock.calls.length, 1);
const call = sum.mock.calls[0];
assert.deepStrictEqual(call.arguments, [3, 4]);
assert.strictEqual(call.result, 7);
assert.strictEqual(call.error, undefined);
// Reset the globally tracked mocks.
mock.reset();
});
'use strict';
const assert = require('node:assert');
const { mock, test } = require('node:test');
test('spies on a function', () => {
const sum = mock.fn((a, b) => {
return a + b;
});
assert.strictEqual(sum.mock.calls.length, 0);
assert.strictEqual(sum(3, 4), 7);
assert.strictEqual(sum.mock.calls.length, 1);
const call = sum.mock.calls[0];
assert.deepStrictEqual(call.arguments, [3, 4]);
assert.strictEqual(call.result, 7);
assert.strictEqual(call.error, undefined);
// Reset the globally tracked mocks.
mock.reset();
});
The same mocking functionality is also exposed on the TestContext
object
of each test. The following example creates a spy on an object method using the
API exposed on the TestContext
. The benefit of mocking via the test context is
that the test runner will automatically restore all mocked functionality once
the test finishes.
test('spies on an object method', (t) => {
const number = {
value: 5,
add(a) {
return this.value + a;
},
};
t.mock.method(number, 'add');
assert.strictEqual(number.add.mock.calls.length, 0);
assert.strictEqual(number.add(3), 8);
assert.strictEqual(number.add.mock.calls.length, 1);
const call = number.add.mock.calls[0];
assert.deepStrictEqual(call.arguments, [3]);
assert.strictEqual(call.result, 8);
assert.strictEqual(call.target, undefined);
assert.strictEqual(call.this, number);
});