I have a function as follows:
async foo() : Promise<Object> {
if(...) throw new Error
}
How am I supposed to test that the error is thrown? Currently I'm doing this:
it("testing for error thrown", async function () {
expect(async() => await foo()).to.throw(Error)
})
You can do something like this and if the error is thrown, the test will fail.
const foo = async (): Promise<Object> => {
// If you want the test to fail increase x to 11
const x = 0
if (x > 10) {
throw Error('Test will fail')
}
// Add meaningful code this is just an example
return { some: 'object' }
}
it('testing for error thrown', async () => {
const object = await foo()
expect(object).toEqual({ some: 'object' })
})
Try this:
it("testing for error thrown", async function () {
await expect(foo()).rejects.toThrow(Error)
})
Since you mentioned chai-as-promised, you would use either:
expect(promise).to.eventually.be.rejected
or:
promise.should.be.rejected
There's also rejectedWith() which lets you specify the Error class/constructor.
Here's a demo:
mocha.setup('bdd');
mocha.checkLeaks();
let { expect } = chai;
chai.should();
let chaiAsPromised = module.exports; /* hack due to lack of UMD file, only for SO */
chai.use(chaiAsPromised);
async function foo(){
throw new Error();
}
describe('Asynchronous Function', function(){
it('Expect and Eventually', function(){
return expect(foo()).to.eventually.be.rejected;
})
it('With Should', function(){
return foo().should.be.rejected;
});
});
mocha.run();.as-console {
display: none !important;
}<script>
window.module = {}; function require(){ return {} }; /* hack due to lack of UMD file, only for SO */
</script>
<script src="https://cdn.jsdelivr.net/npm/chai-as-promised@7.1.1/lib/chai-as-promised.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/mocha/9.1.1/mocha.min.js"></script>
<script src="https://unpkg.com/chai@4.3.4/chai.js"></script>
<link rel="stylesheet" href="https://unpkg.com/mocha/mocha.css" />
<div id="mocha"></div>