Namespaced function not running on PHPUnit test - php

Question

I'm trying to override a built in php function using a namespaced test like this:
Original Class:
<?php
namespace My\Namespace;
class OverrideCommand
{
public function myFileExists($path)
{
return file_exists($path);
}
}
Unit Test
<?php
namespace My\Namespace\Test\Unit\Console\Command;
function file_exists($path)
{
return true;
}
class OverrideCommandTest extends \PHPUnit_Framework_TestCase
{
/**
* #var OverrideCommand
*/
protected $command;
protected function setUp()
{
$this->command = new \My\Namespace\OverrideCommand();
}
public function testMyFileExists()
{
$result = $this->command->myFileExists('some/path/file.txt');
$this->assertTrue($result);
}
}
In this case the file_exists function in my test should always return true, however when I run PHPUnit I get:
PHPUnit 5.7.21 by Sebastian Bergmann and contributors.
There was 1 failure:
1) My\Namespace\Test\Unit\Console\Command\OverrideCommandTest::testMyFileExists
Failed asserting that false is true.
It's as if the namespaced function is being ignored and it's just calling the built in function instead, am I missing something?

Answer 1

According to your code sample, you define the function file_exists() in the namespace My\Namespace\Test\Unit\Console\Command:
namespace My\Namespace\Test\Unit\Console\Command;
function file_exists($path)
{
return true;
}
so of course, you actually never override the function file_exists() in the root namespace.
As far as I know, you can't do that. Whenever you would try to define a function that already exists, a fatal error will be triggered, see https://3v4l.org/JZHcp.
However, if what you want to achieve is asserting that OverrideCommand::myFileExists() returns true if a file exists, and false if it doesn't, you can do one of the following
Refer to files which do and do not exist in your test
public function testMyFileExistsReturnsFalseIfFileDoesNotExist()
{
$command = new OverrideCommand();
$this->assertTrue($command->myFileExists(__DIR__ . '/NonExistentFile.php');
}
public function testMyFileExistsReturnsTrueIfFileExists()
{
$command = new OverrideCommand();
$this->assertTrue($command->myFileExists(__FILE__);
}
Mock the file system
Use https://github.com/mikey179/vfsStream to mock the file system.
Note: For your example, I would recommend the former.