Add comprehensive tests for LazyCollection diff methods

This commit adds thorough tests for three key diff methods in the LazyCollection class:

1. testDiffAssoc: Tests the diffAssoc method which returns items that exist in the
   original collection but not in the given collection, comparing both keys and values.

2. testDiffKeys: Tests the diffKeys method which returns items from the original
   collection whose keys don't exist in the given collection.

3. testDiffKeysUsing: Tests the diffKeysUsing method with a custom comparison callback
   that groups keys by hundreds, demonstrating how to implement custom key comparison logic.

These tests ensure proper functionality of collection difference operations and verify
that each method returns a new LazyCollection instance.

Author: mohammadrasoulasghari

tests/Support/SupportLazyCollectionTest.php

@@ -456,14 +456,14 @@ public function testDiff()
                 'Jeffrey Way',
                 'Adam Wathan',
                 'Caleb Porzio',
-                'Mohamed Said'
+                'Mohamed Said',
             ]);
 
         $diff = $collection->diff(
             [
                 'Jeffrey Way',
                 'Caleb Porzio',
-                'Nuno Maduro'
+                'Nuno Maduro',
             ]);
 
         $this->assertEquals([0 => 'Taylor Otwell', 2 => 'Adam Wathan', 4 => 'Mohamed Said'], $diff->all());
@@ -484,4 +484,82 @@ public function testDiffUsing()
 
         $this->assertEquals([1 => 20, 2 => 30, 3 => 40], $diff2->all());
     }
+
+    public function testDiffAssoc()
+    {
+        $collection = new LazyCollection([
+            'name' => 'Laravel',
+            'version' => '10.0',
+            'type' => 'framework',
+            'license' => 'MIT',
+            'features' => 'Eloquent',
+        ]);
+
+        $diff = $collection->diffAssoc([
+            'name' => 'Laravel',
+            'version' => '9.0',
+            'type' => 'framework',
+            'author' => 'Taylor Otwell',
+            'features' => 'Blade',
+        ]);
+
+        $this->assertEquals(
+            [
+                'version' => '10.0',
+                'license' => 'MIT',
+                'features' => 'Eloquent',
+            ],
+            $diff->all()
+        );
+
+        $this->assertInstanceOf(LazyCollection::class, $diff);
+    }
+
+    public function testDiffKeys()
+    {
+        $collection = new LazyCollection([
+            'one' => 'Laravel',
+            'two' => 'Livewire',
+            'three' => 'Blade',
+            'four' => 'Eloquent',
+            'five' => 'Forge',
+        ]);
+
+        $diff = $collection->diffKeys([
+            'two' => 'Something else',
+            'four' => 'Completely different value',
+            'six' => 'Nova',
+        ]);
+
+        $this->assertEquals(
+            [
+                'one' => 'Laravel',
+                'three' => 'Blade',
+                'five' => 'Forge',
+            ],
+            $diff->all()
+        );
+        $this->assertInstanceOf(LazyCollection::class, $diff);
+    }
+
+    public function testDiffKeysUsing()
+    {
+        $collection = new LazyCollection([
+            100 => 'Route definition',
+            200 => 'Middleware',
+            300 => 'Controller',
+            400 => 'Model',
+        ]);
+
+        $diff = $collection->diffKeysUsing([
+            150 => 'Something',
+            250 => 'Something else',
+            350 => 'Another thing',
+        ], function ($a, $b) {
+            return (int) ($a / 100) - (int) ($b / 100);
+        });
+
+        $this->assertEquals([400 => 'Model'], $diff->all());
+        $this->assertInstanceOf(LazyCollection::class, $diff);
+    }
 }