Advanced & Flexible JSON Test Assertions

We might also want to test that we get the correct fields in the response for each item. Can we do that with JMESPath? Sure! The assertJsonMatches() method is really handy. And actually, if you hold command or control and click into it, when we call assertJsonMatches(), behind the scenes, it calls $this->json(). This creates a Json object... which has even more useful methods. The Browser instance itself gives us access to assertJsonMatches(). But if we want to use any of its other methods, we need to do a bit more work.

The first way to use the Json object is via Browser's use() method. Pass this a callback with a Json $json argument.

This is a magic feature of browser: it reads the type-hint of the argument, and knows to pass us the Json object. You could also type-hint a CookieJar object, Crawler or a few other things.

The point is: because we type-hinted the argument with Json, it will grab the Json object for the last response and pass it to us. Let's use it to do some experimenting. We want to check what the keys are for the first item inside of hydra:member. To help figure the expression we need, let's use a method called search(). This allows us to use a JMESPath expression and get back the result. Do double quotes then hydra:member to see what it returns. And... remove the other dump.

Ok! Run that test again:

symfony php bin/phpunit

It passes... but more importantly, look at the dump! It's the array of 5 items. Ok... let's grab the 0 index. After the hydra:member double quotes, add [0]. Then surround the entire thing with a keys() function from JMESPath.

Try that now.

symfony php bin/phpunit

Oh that's lovely. And it's probably one of the more complex things that you'll do. Now that we've got the path right, turn that into an assertion. You can do that by setting this to a variable - like $keys - and using a normal assertion. Or you can change search to assertMatches() and pass a second argument: the array of the expected fields.

We should be good! Try it:

symfony php bin/phpunit

It passes! And yes, we could now remove the use() method and move this to a normal ->assertJsonMatches() call.

Doing Normal JSON Assertions

As cool as this JMESPath stuff is, it is another thing to learn and it can get complex. So what's the alternative?

Assign the entire $browser chain to a new $json variable and then add ->json() to the end. Most methods on Browser return... a Browser, which let's us do all the fun chaining. But a few, like ->json() let us "break out" of browser so we can do something custom.

This allows us to remove the use() function here and replace the assertions with more traditional PHPUnit code. We could still use the Json object directly... that passes... or to remove all fanciness, change to $this->assertSame() that $json->decoded()['hydra:member'][0] - array_keys() around everything - matches our array. And of course... that passes to!

So, a lot of power... but also a lot of flexibility to write tests how you want.

Next, let's add tests for authentication: both logging in via our login form and via an API token.