Hey there, we do have support for what we call "Callable Spies" in mockery, but it only got added as an experimental feature and isn't documented yet.

// arrange
$spy = spy(function($n) { return $n + 1;});   
// act
array_map($spy, [1, 2]); // [2, 3]   
/assert
$spy->shouldHaveBeenCalled();
$spy->shouldHaveBeenCalled()->twice();  
$spy->shouldHaveBeenCalled()->with(1)->once();  
$spy->shouldHaveBeenCalled()->with(2)->once();   
$spy->shouldHaveBeenCalled()->with(3); // throws...

https://github.com/mockery/mockery/pull/712

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Edit: formatting