replace mock by spy

tests/IfEmptyTest.php

@@ -3,30 +3,27 @@
 namespace Spatie\CollectionMacros\Test;
 
 use Illuminate\Support\Collection;
-use Mockery;
 
 class IfEmptyTest extends TestCase
 {
     /** @test */
     public function it_executes_the_callable_if_the_collection_is_empty()
     {
-        $mock = Mockery::mock();
-        $mock->shouldReceive('someCall')->once();
-
-        Collection::make()->ifEmpty(function () use ($mock) {
-            $mock->someCall();
+        Collection::make()->ifEmpty(function () {
+            $this->spy->someCall();
         });
+
+        $this->spy->shouldHaveReceived('someCall')->once();
     }
 
     /** @test */
     public function it_doesnt_execute_the_callable_if_the_collection_isnt_empty()
     {
-        $mock = Mockery::mock();
-        $mock->shouldNotReceive('someCall');
-
-        Collection::make(['foo'])->ifEmpty(function () use ($mock) {
-            $mock->someCall();
+        Collection::make(['foo'])->ifEmpty(function () {
+            $this->spy->someCall();
         });
+
+        $this->spy->shouldNotHaveReceived('someCall');
     }
 
     /** @test */