How are integration tests written for interacting with external API?

问题

First up, where my knowledge is at:

Unit Tests are those which test a small piece of code (single methods, mostly).

Integration Tests are those which test the interaction between multiple areas of code (which hopefully already have their own Unit Tests). Sometimes, parts of the code under test requires other code to act in a particular way. This is where Mocks & Stubs come in. So, we mock/stub out a part of the code to perform very specifically. This allows our Integration Test to run predictably without side effects.

All tests should be able to be run stand-alone without data sharing. If data sharing is necessary, this is a sign the system isn't decoupled enough.

Next up, the situation I am facing:

When interacting with an external API (specifically, a RESTful API that will modify live data with a POST request), I understand we can (should?) mock out the interaction with that API (more eloquently stated in this answer) for an Integration Test. I also understand we can Unit Test the individual components of interacting with that API (constructing the request, parsing the result, throwing errors, etc). What I don't get is how to actually go about this.

So, finally: My question(s).

How do I test my interaction with an external API that has side effects?

A perfect example is Google's Content API for shopping. To be able to perform the task at hand, it requires a decent amount of prep work, then performing the actual request, then analysing the return value. Some of this is without any 'sandbox' environment.

The code to do this generally has quite a few layers of abstraction, something like:

<?php
class Request
{
    public function setUrl(..){ /* ... */ }
    public function setData(..){ /* ... */ }
    public function setHeaders(..){ /* ... */ }
    public function execute(..){
        // Do some CURL request or some-such
    }   
    public function wasSuccessful(){
        // some test to see if the CURL request was successful
    }   
}

class GoogleAPIRequest
{
    private $request;
    abstract protected function getUrl();
    abstract protected function getData();

    public function __construct() {
        $this->request = new Request();
        $this->request->setUrl($this->getUrl());
        $this->request->setData($this->getData());
        $this->request->setHeaders($this->getHeaders());
    }   

    public function doRequest() {
        $this->request->execute();
    }   
    public function wasSuccessful() {
        return ($this->request->wasSuccessful() && $this->parseResult());
    }   
    private function parseResult() {
        // return false when result can't be parsed
    }   

    protected function getHeaders() {
        // return some GoogleAPI specific headers
    }   
}

class CreateSubAccountRequest extends GoogleAPIRequest
{
    private $dataObject;

    public function __construct($dataObject) {
        parent::__construct();
        $this->dataObject = $dataObject;
    }   
    protected function getUrl() {
        return "http://...";
    }
    protected function getData() {
        return $this->dataObject->getSomeValue();
    }
}

class aTest
{
    public function testTheRequest() {
        $dataObject = getSomeDataObject(..);
        $request = new CreateSubAccountRequest($dataObject);
        $request->doRequest();
        $this->assertTrue($request->wasSuccessful());
    }
}
?>

Note: This is a PHP5 / PHPUnit example

Given that testTheRequest is the method called by the test suite, the example will execute a live request.

Now, this live request will (hopefully, provided everything went well) do a POST request that has the side effect of altering live data.

Is this acceptable? What alternatives do I have? I can't see a way to mock out the Request object for the test. And even if I did, it would mean setting up results / entry points for every possible code path that Google's API accepts (which in this case would have to be found by trial and error), but would allow me the use of fixtures.

A further extension is when certain requests rely on certain data being Live already. Using the Google Content API as an example again, to add a Data Feed to a Sub Account, the Sub Account must already exist.

One approach I can think of is the following steps;

In testCreateAccount
1. Create a sub-account
2. Assert the sub-account was created
3. Delete the sub-account
Have testCreateDataFeed depend on testCreateAccount not having any errors
1. In testCreateDataFeed, create a new account
2. Create the data feed
3. Assert the data feed was created
4. Delete the data feed
5. Delete the sub-account

This then raises the further question; how do I test the deletion of accounts / data feeds? testCreateDataFeed feels dirty to me - What if creating the data feed fails? The test fails, therefore the sub-account is never deleted... I can't test deletion without creation, so do I write another test (testDeleteAccount) that relies on testCreateAccount before creating then deleting an account of its own (since data shouldn't be shared between tests).

In Summary

How do I test interacting with an external API that effects live data?
How can I mock / stub objects in an Integration test when they're hidden behind layers of abstraction?
What do I do when a test fails and the live data is left in an inconsistent state?
How in code do I actually go about doing all this?

How can mocking external services improve unit tests?
Writing unit tests for a REST-ful API

回答1:

This is more an additional answer to the one already given:

Looking through your code, the class GoogleAPIRequest has a hard-encoded dependency of class Request. This prevents you from testing it independently from the request class, so you can't mock the request.

You need to make the request injectable, so you can change it to a mock while testing. That done, no real API HTTP requests are send, the live data is not changed and you can test much quicker.

回答2:

I've recently had to update a library because the api it connects to was updated.

My knowledge isn't enough to explain in detail, but i learnt a great deal from looking at the code. https://github.com/gridiron-guru/FantasyDataAPI

You can submit a request as you would normally to the api and then save that response as a json file, you can then use that as a mock.

Have a look at the tests in this library which connects to an api using Guzzle.

It mocks responses from the api, there's a good deal of information in the docs on how the testing works it might give you an idea of how to go about it.

but basically you do a manual call to the api along with any parameters you need, and save the response as a json file.

When you write your test for the api call, send along the same parameters and get it to load in the mock rather than using the live api, you can then test the data in the mock you created contains the expected values.

My Updated version of the api in question can be found here. Updated Repo

回答3:

One of the ways to test out external APIs is as you mentioned, by creating a mock and working against that with the behavior hard coded as you have understood it.

Sometimes people refer to this type of testing as "contract based" testing, where you can write tests against the API based on the behavior you have observed and coded against, and when those tests start failing, the "contract is broken". If they are simple REST based tests using dummy data you can also provide them to the external provider to run so they can discover where/when they might be changing the API enough that it should be a new version or produce a warning about not being backwards compatible.

Ref: https://www.thoughtworks.com/radar/techniques/consumer-driven-contract-testing

回答4:

Building on top of what the high voted answer says.... Here's how I've done it and works quiet well.

Created a mock curl object
Tell the mock what parameters it would be expecting
Mock out what the response of the curl call within your function will be

Let your code do it's thing

$curlMock = $this->getMockBuilder('\Curl\Curl')
                 ->setMethods(['get'])
                 ->getMock();

$curlMock
    ->expects($this->once())
    ->method('get')
    ->with($URL .  '/users/' . urlencode($userId));

$rawResponse = <<<EOL
{
     "success": true,
     "result": {
     ....
     }
}
EOL;

$curlMock->rawResponse = $rawResponse;
$curlMock->error = null;

$apiService->curl = $curlMock;

// call the function that inherently consumes the API via curl
$result = $apiService->getUser($userId);

$this->assertTrue($result);

来源：https://stackoverflow.com/questions/7564038/how-are-integration-tests-written-for-interacting-with-external-api

标签

unit-testing

api

rest

phpunit

integration-testing