Mock an object created in the middle of a method - php

Question

I know that creating an instance of a Class in the middle of a method it's a bad practice since it makes code hard to test.
But I can't refactor the code, so I need to find a way to mock an Object created with new in the middle of a method under test.
Used Frameworks: PHPUnit, Mockery, WP_Mock
Example: Here I need to mock the get_second_string() method from the instance of the class ExternalClass
Class MyClass {
function methodUnderTest($string) {
$objToMock = new ExternalClass();
$second_string = $objToMock->get_second_string();
$final_string = $string . $second_string;
return $final_string;
}
}
Class TestMyClass extends PHPUnit_Framework_TestCase {
public function setUp() {
}
public function tearDown() {
}
public function test_methodUnderTest() {
$externalObject = $this->getMockBuilder('ExternalClass')
->setMethods(['get_second_string'])
->getMock;
$externalObject->expects($this->once())
->method('get_second_string')
->willReturn(' two');
$testObj = new MyClass();
$this->assertEquals('one two', $testObj->methodUnderTest('one');
}
}

Answer 1

If you really have no opportunity to refactor the code or do some appropriate integration testing, you might want to take a look at https://github.com/php-test-helpers/php-test-helpers#intercepting-object-creation and https://github.com/krakjoe/uopz/tree/PHP5
Still I think the code you make would profit a lot more from refactoring than monkey patching.
Besides, the refactoring does not need to be very heavy. You might do at least this:
class MyClass
{
private $externalsFactory;
public function __construct($externalsFactory){
$this->externalsFactory = $externalsFactory;
}
public function methodUnderTest($str){
$external = $this->externalsFactory->make();
$second_string = $external->get_second_string();
$finalString = $str.$second_string;
return $finalString;
}
}
class ExternalsFactory
{
public function make(){
return new ExternalClass();
}
}
class ExternalClass
{
public function get_second_string(){
return 'some real stuff may be even from database or whatever else it could be';
}
}
class MyClassTest extends PHPUnit_Framework_TestCase
{
private $factoryMock;
private $myClass;
public function setUp(){
$this->factoryMock = $this->getMockBuilder('ExternalsFactory')
->getMock();
$this->myClass = new MyClass($this->factoryMock);
}
public function testMethodUnderTest(){
$extenalMock = $this->createMock('ExternalClass');
$extenalMock->method('get_second_string')
->willReturn('second');
$this->factoryMock->method('make')
->willReturn($extenalMock);
$this->assertSame('first-and-second', $this->myClass->methodUnderTest('first-and-'));
}
}

Answer 2

IMHO there is no way to do such a thing. You should pass the object as parameter to the method.

Answer 3

You can not mock entire object.
But with phpunit you can do something like this:
$f = $this->getMockBuilder(<your_class>)->disableOriginalConstructor()
->setMethods(array(
<mocked_method_1>, <mocked_method_2>
))->getMock();
This way, newly created object ommits constructor and you specify which method are going to behave normally and which you mock.
in testing you can specify what the method/s will return, like this:
$f->method(<mocked_method_1>)->willReturn(<dummy_data>);
using this, you will not test the mocked object in any way, but can test method which is creating the object..