PHPUnit function toArray() of mocked ArrayCollection returns null

The toArray() function of the ArrayCollection class in PHPUnit returns null when called on a mocked instance of the class. This is because the toArray() function is not implemented in the mock object.

To fix this issue, you can stub the toArray() function to return an array. For example:

$arrayCollection = $this->getMockBuilder(ArrayCollection::class)
    ->disableOriginalConstructor()
    ->getMock();

$arrayCollection->method('toArray')
    ->willReturn(['foo', 'bar']);

$this->assertEquals(['foo', 'bar'], $arrayCollection->toArray());

Note: The disableOriginalConstructor() method is used to prevent the mock object from calling the original constructor of the ArrayCollection class. This is necessary because the original constructor initializes the ArrayCollection object with an empty array, which would cause the toArray() function to return null.

# Summary

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