UnitTesting\FunctionSpy

Sometimes you want to unit test a global or native PHP method, especially when working with a package that has a bunch of globally defined functions (like Wordpress).

Inspiration was taken from javascript testing module: https://github.com/jasmine/jasmine.

Installation

• composer require --dev unit-testing/function-spy:dev-master
• Or, require the module in your composer.json like this: "require-dev": { "unit-testing/function-spy": "dev-master" } and run composer update

Spy

The Spy class is a static container that fires up an instance of Registry. It has one defined static method instance to instantiate or to get the bound instance of Registry. All other static calls are forwarded onto the Registry instance.

You will only ever need to use the static method when mocking a function or class method you're trying to test:

<?php namespace MyNamespace;

class TestCase extends \PHPUnit_Framework_TestCase {
	use \UnitTesting\FunctionSpy\SpyTrait;

	function test_functionOrMethod_CanBeSpied()
	{
		function_under_test('foo');
		$this->assertFunctionLastCalledWith('function_under_test', array('foo'));

		$instance = new FakeInstanceThatHasMethodWhichCallsFunctionUnderTest();
		$instance->methodWhichCallsFunctionUnderTest('bar');
		$this->assertFunctionLastCalledWith('function_under_test', array('bar'));
	}
}

function function_under_test()
{
	\UnitTesting\FunctionSpy\Spy::function_under_test();
}

class FakeInstanceThatHasMethodWhichCallsFunctionUnderTest {

	function methodWhichCallsFunctionUnderTest($param)
	{
		function_under_test($param);
	}
}

Registry

Registry is responsible for logging all spied function calls and their respective arguments. It also has some functions to perform some more in depth analysis.

• getRecorders returns an array with all the functions that have been spied upon. Each key in the array is a function name and has an instance of Recorder as its value.
• getRecorder($name) gets the Recorder instance for the matching function call or null if no calls to that function were made.
• flushRecorders explicitly empties the array of recorders
• setFunctionResult($name, $result) creates an instance of Recoder for the function (if not already created) and sets return values for that function
• For convenience, the Registry instance implements ArrayAccess to access/instantiate spies or set their results.

Recorder

• getCalls get all the calls and their respective argument lists
• wasCalled checks if the method was called or not
• wasCalledWith checks to see if the method was called with a specific list of arguments
• wasLastCalledWith checks to see if the method's last call matches a specific list of argumetns

SpyTrait

The SpyTrait is a simple trait that can be useed by any of your PHPUnit test cases to automatically set up and flush the Registry. With a few lines of code, it will instantiate Registry and set a $spy property on your test case for easy access from within your tests. It also extends your test case with a few assertion methods to help check that global function was called.

• protected initSpy: call this from within your setUp() method to initialize the spy and set the $spy member
• protected flushSpy: call this from within your tearDown() method to clear all calls to empty all calls to the spy between each test.
• assertFunctionNotCalled: ensure that a global function was NOT called
• assertFunctionNotCalledWith: ensure that a global function was NOT called with certain parameters
• assertFunctionCalledWith: ensure that a global function was called with certain parameters
• assertFunctionLastCalledWith: ensure that a global function was most recently called with certain parameters

Annotated example

Let's say there is a method doSomethting that you've inherited and have to work with. You want to ensure that it is called when it should be with the parameters that it should be called with. Your class MyNamespace\MyClass has a method doFoo which conditionally calls the doSomething function and returns its result.

Subject Under Test

<?php namespace MyNamespace;
class MyClass {
	public function doFoo($param1, $param2)
	{
		if ($param1 == 'bar')
		{
			return doSomething($param1, $params);
		}
	}
}

Test Case

<?php namespace MyNamespace;
class MyTest extends \PHPUnit_Framework_TestCase {
	// Use the trait
	use \UnitTesting\FunctionSpy\SpyTrait;

	protected function setUp()
	{
		// init the spy
		$this->initSpy();
	}
	protected function tearDown()
	{
		// flush the spy so we can reset the calls after every test
		$this->flushSpy();
	}

	function test_doFoo_WithBar_CallsDoSomethingWithBar()
	{
		$myClass = new MyClass();

		$myClass->doFoo('bar', 'baz');

		// we've ensured that the doSomething() method has been called with bar and baz
		$this->assertFunctionLastCalledWith('doSomething', array('bar', 'baz'));
	}

	function test_doFoo_WithBar_ReturnsResultOfDoSomething()
	{
		// we'll set the result for the function doSomething() to return "doSomething result"
		$this->spy['doSomething']->setResult('doSomething result');
		// alternatively, you can also just assign set the property:
		// $this->spy['doSomething'] = 'doSomething result';

		$myClass = new MyClass();

		$result = $myClass->doFoo('bar', 'baz');

		// we ensure that the doFoo() method returns the result of doSomething();
		$this->assertEquals('doSomething result', $result);
	}

	function doFoo_WithBaz_NeverCallsDoSomething()
	{
		$myClass = new MyClass();

		$myClass->doFoo('some param which does not call doSomething');

		// ensure that doSomething() is never called
		$this->assertFunctionNotCalled('doSomething');
	}

}

// this is needed because we're overriding the globally defined doSomething within our namespace.
function doSomething()
{
	// the Spy static class allows you to simply call any method name and it will log the call with that name.
	// if you don't explicity pass parameters, it will attempt to guess the passed parameters to this function
	// using debug_backtrace()
	return Spy::doSomething();
}

Acknowledgements

Other packages/references which address this testing problem and used as reference:

• https://github.com/lstrojny/phpunit-function-mocker
• http://www.schmengler-se.de/en/2011/03/php-mocking-built-in-functions-like-time-in-unit-tests/
• http://marcelog.github.io/articles/php_mock_global_functions_for_unit_tests_with_phpunit.html