Some example on a simple PHPUnit Mock. Meant as answer to this question: https://twitter.com/Rarst/status/618880034145718272

ReleaseTest.php

<?php

class ReleaseTest \PHPUnit_Framework_TestCase {

  public function testConstructor() {
    
    $splFileInfoMock = $this->getMockBuilder( 'SplFileInfo' )
      ->disableOriginalConstructor()
      ->getMock();
      
    //define the behaviour of the mock
    $splFileInfoMock->expects( $this->any() )
      ->method( 'getRelativePath' )
      ->willReturn( 'your/testing/path' );
      
    $testee = new Rarst\ReleaseBelt\Release( $splFileMock );
    
    // now test the public properties with assertions.
  }
}