Pact Foundation

Hi there, I'm trying to run a test scenario where a parameter is passed in an invalid format (and it should throw a 400), but it fails with the error message `with 30000 ms timeout for Pact`. I've tried to increase the timeout (quite significantly but it still fails with the same message).

Is there any way to check why it times out? It seems due to a promise that doesn't resolve...

Also it seems to be specifically when looking to get the provider to respond with status 400 :thinking_face:

Code snippet in :thread:

```it('should return an error when an invalid UPRN is passed', async () =&gt; {
            await provider.addInteraction({
                uponReceiving: 'an invalid UPRN',
                withRequest: {
                    method: 'GET',
                    path: '/property/m1xf%d5/sales'
                },
                willRespondWith: {
                    status: 400,
                    headers: default_headers,
                    body: {
                        error: 'BadRequest',
                        message: 'Invalid UPRN format',
                        statusCode: 400
                    }
                }
            });

            process.env.API_PROPERTY_TRANSACTIONS_URL =
                provider.mockService.baseUrl;

            const response = await api().transactionalHistoryByUprn('m1xf%d5');
            expect(response).toThrow('400: Bad Request');
        });```


```const response = await api().transactionalHistoryByUprn('m1xf%d5'); &lt;- throws
expect(response).toThrow('400: Bad Request'); &lt;- to late, already thrown!```


You can actually see the error in your terminal

You might need to wrap it like this:

```expect(() =&gt; {
  throw Error();
}).toThrow();```


```expect(() =&gt; api().transactionalHistoryByUprn('m1xf%d5')).toThrow('400: Bad Request');```

I could be wrong about the jest syntax, so best to check the `toThrow` docs. You might be able to just hand it a promise. But you are `await` ing the promise, so that will always throw before the `expect`

<https://jestjs.io/docs/asynchronous|https://jestjs.io/docs/asynchronous>

await expect(fetchData()).rejects.toMatch('error');

Thanks Matt, I wrapped it as suggested and it worked :slightly_smiling_face:

I’ve just added an example to the JS troubleshooting guide for others (this exact problem came up in hte very next post :laughing: <https://github.com/pact-foundation/pact-js/blob/master/docs/troubleshooting.md#how-do-i-test-negative-scenarios-such-as-400>