PHP Matcher with Behat to assert unpredictable Json

PHP Matcher is an awesome library to do assertion against unpredictable data. Combined with Behat and the Behatch contexts it’s the perfect tool to test for non-deterministic JSON payload.

Here is an example where I override a method of Behatch JsonContext to add PHP Matcher features:

<?php

use Behat\Gherkin\Node\PyStringNode;
use Behat\Mink\Exception\ExpectationException;
use Behatch\Context\JsonContext as BehatchJsonContext;
use Coduo\PHPMatcher\PHPMatcher;

class JsonContext extends BehatchJsonContext
{
    public function theJsonShouldBeEqualTo(PyStringNode $content)
    {
        $actual = $this->getJson();

        // Replace all useless whitespace
        // You can use the \Behatch\Json\Json class to have the same behavior
        // but it checks JSON syntax which could be problematic if you want to get rid
        // of double quote in field value
        $expected = preg_replace('/\s(?=([^"]*"[^"]*")*[^"]*$)/', '', $content->getRaw());

        if (!PHPMatcher::match((string) $actual, (string) $expected, $error)) {
            throw new ExpectationException($error, $this->getSession());
        }
    }
}

Then you need to use this context in your behat.yml.dist instead of the one provided by Behatch:

default:
    suites:
        default:
            contexts:
                - JsonContext

Now, all your feature files can use PHP Matcher features like the following:

Feature:
  Scenario: Client credentials authentication
    When I send a "GET" request to "/foo"
    Then the response should be in JSON
    And the header "Content-Type" should be equal to "application/json"
    And the response status code should be 200
    And the JSON should be equal to:
    """
    {
      "bar":"@uuid@"
    }
    """

Let me know in the comment section below if you know any other alternative ;-)

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