Question

我正在写一些expect.js匹配器，我想亲自测试匹配器。所以我想写积极和消极的测试。假设我写了

toContainItem(name);

像这样使用;

expect(femaleNames).toContainItem('Brad'); // test fails
expect(femaleNames).toContainItem('Angelina'); // test passes

我想做的是为负面案例写一个测试，就像这样;

 it('should fail if the item is not in the list', function() {
     expect(function() {
         expect(femaleNames).toContainItem('Brad'); 
     }).toFailTest('Could not find "Brad" in the array');
 });

我不确定如何在不会使包含测试失败的环境中运行我的失败测试代码。这可能吗？

编辑：根据Carl Manaster的回答，我想出了一个期望的扩展，允许上面的代码工作;

expect.extend({
    toFailTest(msg) {
        let failed = false;
        let actualMessage = "";
        try
        {
            this.actual();
        } 
        catch(ex)
        {
            actualMessage = ex.message;
            failed = true;
        }

        expect.assert(failed, 'function should have failed exception');

        if(msg) {
            expect.assert(actualMessage === msg, `failed test: expected "${msg}" but was "${actualMessage}"`);
        }
    }
});

Answer 1

我认为你可以在try / catch块中包含内部expect，你可以在catch子句中清除失败变量，然后对变量的值进行实际断言。

let failed = true;
try {
  expect(femaleNames).toContainItem('Brad');
} catch (e) {
  failed = false;
}
expected(failed).toBe(false);

测试expect.js的扩展

1 个答案: