mock.method(object, methodName[, implementation][, options])

• object <Object> 其方法被模拟的对象。
• methodName <string> | <symbol> 要模拟的 object 上的方法的标识符。 如果 object[methodName] 不是函数，则会抛出错误。
• implementation <Function> | <AsyncFunction> 用作 object[methodName] 的模拟实现的可选函数。 默认值: object[methodName] 指定的原始方法。
• options <Object> 模拟方法的可选配置选项。 支持以下属性：
  • getter <boolean> 如果为 true，object[methodName] 被当作获取器。 此选项不能与 setter 选项一起使用。 默认值： false。
  • setter <boolean> 如果为 true，object[methodName] 被视为设置器。 此选项不能与 getter 选项一起使用。 默认值： false。
  • times <integer> 模拟将使用 implementation 的行为的次数。 一旦被模拟的方法被调用了 times 次，它会自动恢复原来的行为。 此值必须是大于零的整数。 默认值: Infinity。
• 返回: <Proxy> 被模拟的方法。 模拟方法包含一个特殊的 mock 属性，它是 MockFunctionContext 的实例，可用于检查和更改模拟方法的行为。

此函数用于在现有对象方法上创建模拟。 以下示例演示了如何在现有对象方法上创建模拟。

test('spies on an object method', (t) => {
  const number = {
    value: 5,
    subtract(a) {
      return this.value - a;
    },
  };

  t.mock.method(number, 'subtract');
  assert.strictEqual(number.subtract.mock.calls.length, 0);
  assert.strictEqual(number.subtract(3), 2);
  assert.strictEqual(number.subtract.mock.calls.length, 1);

  const call = number.subtract.mock.calls[0];

  assert.deepStrictEqual(call.arguments, [3]);
  assert.strictEqual(call.result, 2);
  assert.strictEqual(call.error, undefined);
  assert.strictEqual(call.target, undefined);
  assert.strictEqual(call.this, number);
});

• object <Object> The object whose method is being mocked.
• methodName <string> | <symbol> The identifier of the method on object to mock. If object[methodName] is not a function, an error is thrown.
• implementation <Function> | <AsyncFunction> An optional function used as the mock implementation for object[methodName]. Default: The original method specified by object[methodName].
• options <Object> Optional configuration options for the mock method. The following properties are supported:
  • getter <boolean> If true, object[methodName] is treated as a getter. This option cannot be used with the setter option. Default: false.
  • setter <boolean> If true, object[methodName] is treated as a setter. This option cannot be used with the getter option. Default: false.
  • times <integer> The number of times that the mock will use the behavior of implementation. Once the mocked method has been called times times, it will automatically restore the original behavior. This value must be an integer greater than zero. Default: Infinity.
• Returns: <Proxy> The mocked method. The mocked method contains a special mock property, which is an instance of MockFunctionContext, and can be used for inspecting and changing the behavior of the mocked method.

This function is used to create a mock on an existing object method. The following example demonstrates how a mock is created on an existing object method.

test('spies on an object method', (t) => {
  const number = {
    value: 5,
    subtract(a) {
      return this.value - a;
    },
  };

  t.mock.method(number, 'subtract');
  assert.strictEqual(number.subtract.mock.calls.length, 0);
  assert.strictEqual(number.subtract(3), 2);
  assert.strictEqual(number.subtract.mock.calls.length, 1);

  const call = number.subtract.mock.calls[0];

  assert.deepStrictEqual(call.arguments, [3]);
  assert.strictEqual(call.result, 2);
  assert.strictEqual(call.error, undefined);
  assert.strictEqual(call.target, undefined);
  assert.strictEqual(call.this, number);
});