From c3916ea707364c8bfa7594f127921aa4c51b1924 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 15:00:54 -0400
Subject: [PATCH 01/28] feat: Add mutation testing configuration and update
 `PHPUnit` schema location.

---
 .github/workflows/mutation.yml         | 24 ++++++++++++++++++++++++
 composer.json                          |  3 +++
 infection.json.dist => infection.json5 | 15 +++++++--------
 phpunit.xml.dist                       |  2 +-
 4 files changed, 35 insertions(+), 9 deletions(-)
 create mode 100644 .github/workflows/mutation.yml
 rename infection.json.dist => infection.json5 (69%)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
new file mode 100644
index 0000000..0c66610
--- /dev/null
+++ b/.github/workflows/mutation.yml
@@ -0,0 +1,24 @@
+on:
+  pull_request:
+    paths-ignore:
+      - 'docs/**'
+      - 'README.md'
+      - 'CHANGELOG.md'
+      - '.gitignore'
+      - '.gitattributes'
+
+  push:
+    paths-ignore:
+      - 'docs/**'
+      - 'README.md'
+      - 'CHANGELOG.md'
+      - '.gitignore'
+      - '.gitattributes'
+
+name: mutation test
+
+jobs:
+  mutation:
+    uses: php-forge/actions/.github/workflows/infection.yml@main
+    secrets:
+      STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}
diff --git a/composer.json b/composer.json
index 826163d..35d3f24 100644
--- a/composer.json
+++ b/composer.json
@@ -15,6 +15,7 @@
     },
     "require-dev": {
         "ext-simplexml": "*",
+        "infection/infection": "^0.27|^0.29",
         "maglnet/composer-require-checker": "^4.1",
         "phpstan/extension-installer": "^1.4",
         "phpstan/phpstan-strict-rules": "^2.0.3",
@@ -41,6 +42,7 @@
     "config": {
         "sort-packages": true,
         "allow-plugins": {
+            "infection/extension-installer": true,
             "phpstan/extension-installer": true,
             "yiisoft/yii2-composer": true
         }
@@ -48,6 +50,7 @@
     "scripts": {
         "check-dependencies": "./vendor/bin/composer-require-checker check",
         "ecs": "./vendor/bin/ecs --fix",
+        "mutation": "./vendor/bin/infection --threads=4 --ignore-msi-with-no-mutations --only-covered --min-msi=100 --min-covered-msi=100",
         "rector": "./vendor/bin/rector process src",
         "static": "./vendor/bin/phpstan --memory-limit=512M",
         "tests": "./vendor/bin/phpunit"
diff --git a/infection.json.dist b/infection.json5
similarity index 69%
rename from infection.json.dist
rename to infection.json5
index d06b334..b47e1f0 100644
--- a/infection.json.dist
+++ b/infection.json5
@@ -1,16 +1,15 @@
 {
-    "source": {
-        "directories": [
-            "src"
-        ]
-    },
+    "$schema": "vendor/infection/infection/resources/schema.json",
     "logs": {
         "text": "php:\/\/stderr",
         "stryker": {
             "report": "main"
         }
     },
-    "mutators": {
-        "@default": true
-    }
+    "source": {
+        "directories": [
+            "src"
+        ]
+    },
+    "timeout": 45
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 3ddadb0..2215bca 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phpunit
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.2/phpunit.xsd"
+    xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
     bootstrap="tests/bootstrap.php"
     cacheDirectory="runtime/.phpunit.cache"
     colors="true"

From 023fa506e24f3157fd8c0d9bf83c44662683f21c Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 15:28:33 -0400
Subject: [PATCH 02/28] test: Add test for shifting left and right attributes
 after deleting a leaf node.

---
 tests/NestedSetsBehaviorTest.php | 128 +++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)

diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index d311816..b3ec09b 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1620,4 +1620,132 @@ public function makeRoot(): bool
 
         $node->makeRoot();
     }
+
+    public function testShiftLeftRightAttributesAfterDeleteLeafNode(): void
+    {
+        $this->generateFixtureTree();
+
+        $nodeToDelete = Tree::findOne(4);
+
+        self::assertNotNull(
+            $nodeToDelete,
+            'Node with ID \'4\' should exist before deletion.',
+        );
+        self::assertTrue(
+            $nodeToDelete->isLeaf(),
+            'Node with ID \'4\' should be a leaf node before deletion.',
+        );
+        self::assertEquals(
+            4,
+            $nodeToDelete->getAttribute('lft'),
+            'Node with ID \'4\' should have left value \'4\' before deletion.',
+        );
+        self::assertEquals(
+            5,
+            $nodeToDelete->getAttribute('rgt'),
+            'Node with ID \'4\' should have right value \'5\' before deletion.',
+        );
+
+        $node5 = Tree::findOne(5);
+
+        self::assertNotNull(
+            $node5,
+            'Node with ID \'5\' should exist before deletion.',
+        );
+        self::assertEquals(
+            6,
+            $node5->getAttribute('lft'),
+            'Node with ID \'5\' should have left value \'6\' before deletion.',
+        );
+        self::assertEquals(
+            7,
+            $node5->getAttribute('rgt'),
+            'Node with ID \'5\' should have right value \'7\' before deletion.',
+        );
+
+        $node6 = Tree::findOne(6);
+
+        self::assertNotNull(
+            $node6,
+            'Node with ID \'6\' should exist before deletion.',
+        );
+        self::assertEquals(
+            9,
+            $node6->getAttribute('lft'),
+            'Node with ID \'6\' should have left value \'9\' before deletion.',
+        );
+        self::assertEquals(
+            14,
+            $node6->getAttribute('rgt'),
+            'Node with ID \'6\' should have right value \'14\' before deletion.',
+        );
+
+        $node9 = Tree::findOne(9);
+
+        self::assertNotNull(
+            $node9,
+            'Node with ID \'9\' should exist before deletion.',
+        );
+        self::assertEquals(
+            16,
+            $node9->getAttribute('lft'),
+            'Node with ID \'9\' should have left value \'16\' before deletion.',
+        );
+        self::assertEquals(
+            29,
+            $node9->getAttribute('rgt'),
+            'Node with ID \'9\' should have right value \'29\' before deletion.',
+        );
+
+        $result = $nodeToDelete->delete();
+
+        self::assertEquals(
+            1,
+            $result,
+            'Deleting the leaf node with ID \'4\' should affect exactly one row.',
+        );
+        self::assertNull(
+            Tree::findOne(4),
+            'Node with ID \'4\' should not exist after deletion.',
+        );
+
+        $node5->refresh();
+
+        self::assertEquals(
+            4,
+            $node5->getAttribute('lft'),
+            'Node with ID \'5\' should have left value \'4\' after shifting.',
+        );
+        self::assertEquals(
+            5,
+            $node5->getAttribute('rgt'),
+            'Node with ID \'5\' should have right value \'5\' after shifting.',
+        );
+
+        $node6->refresh();
+
+        self::assertEquals(
+            7,
+            $node6->getAttribute('lft'),
+            'Node with ID \'6\' should have left value \'7\' after shifting.',
+        );
+        self::assertEquals(
+            12,
+            $node6->getAttribute('rgt'),
+            'Node with ID \'6\' should have right value \'12\' after shifting.',
+        );
+
+        $node9->refresh();
+
+        self::assertEquals(
+            14,
+            $node9->getAttribute('lft'),
+            'Node with ID \'9\' should have left value \'14\' after shifting.',
+        );
+        self::assertEquals(
+            27,
+            $node9->getAttribute('rgt'),
+            'Node with ID \'9\' should have right value \'27\' after shifting.',
+        );
+    }
 }

From 1dbbb1732118a5adcc5cbfe912c998f82d0a902e Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 15:45:16 -0400
Subject: [PATCH 03/28] test: Rename test for shifting left and right
 attributes after deleting a leaf node for clarity.

---
 tests/NestedSetsBehaviorTest.php | 126 ++++++-------------------------
 1 file changed, 24 insertions(+), 102 deletions(-)

diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index b3ec09b..c45d324 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1621,131 +1621,53 @@ public function makeRoot(): bool
         $node->makeRoot();
     }
 
-    public function testShiftLeftRightAttributesAfterDeleteLeafNode(): void
+    public function testAfterDeleteShiftsLeftRightAttributesCorrectly(): void
     {
         $this->generateFixtureTree();
 
         $nodeToDelete = Tree::findOne(4);
 
-        self::assertNotNull(
-            $nodeToDelete,
-            'Node with ID \'4\' should exist before deletion.',
-        );
-        self::assertTrue(
-            $nodeToDelete->isLeaf(),
-            'Node with ID \'4\' should be a leaf node before deletion.',
-        );
-        self::assertEquals(
-            4,
-            $nodeToDelete->getAttribute('lft'),
-            'Node with ID \'4\' should have left value \'4\' before deletion.',
-        );
-        self::assertEquals(
-            5,
-            $nodeToDelete->getAttribute('rgt'),
-            'Node with ID \'4\' should have right value \'5\' before deletion.',
-        );
+        self::assertNotNull($nodeToDelete);
+        self::assertTrue($nodeToDelete->isLeaf());
+        self::assertEquals(4, $nodeToDelete->getAttribute('lft'));
+        self::assertEquals(5, $nodeToDelete->getAttribute('rgt'));
 
         $node5 = Tree::findOne(5);
 
-        self::assertNotNull(
-            $node5,
-            'Node with ID \'5\' should exist before deletion.',
-        );
-        self::assertEquals(
-            6,
-            $node5->getAttribute('lft'),
-            'Node with ID \'5\' should have left value \'6\' before deletion.',
-        );
-        self::assertEquals(
-            7,
-            $node5->getAttribute('rgt'),
-            'Node with ID \'5\' should have right value \'7\' before deletion.',
-        );
+        self::assertNotNull($node5);
+        self::assertEquals(6, $node5->getAttribute('lft'));
+        self::assertEquals(7, $node5->getAttribute('rgt'));
 
         $node6 = Tree::findOne(6);
 
-        self::assertNotNull(
-            $node6,
-            'Node with ID \'6\' should exist before deletion.',
-        );
-        self::assertEquals(
-            9,
-            $node6->getAttribute('lft'),
-            'Node with ID \'6\' should have left value \'9\' before deletion.',
-        );
-        self::assertEquals(
-            14,
-            $node6->getAttribute('rgt'),
-            'Node with ID \'6\' should have right value \'14\' before deletion.',
-        );
+        self::assertNotNull($node6);
+        self::assertEquals(9, $node6->getAttribute('lft'));
+        self::assertEquals(14, $node6->getAttribute('rgt'));
 
-        $node9 = Tree::findOne(9);
+        $node3 = Tree::findOne(3);
 
-        self::assertNotNull(
-            $node9,
-            'Node with ID \'9\' should exist before deletion.',
-        );
-        self::assertEquals(
-            16,
-            $node9->getAttribute('lft'),
-            'Node with ID \'9\' should have left value \'16\' before deletion.',
-        );
-        self::assertEquals(
-            29,
-            $node9->getAttribute('rgt'),
-            'Node with ID \'9\' should have right value \'29\' before deletion.',
-        );
+        self::assertNotNull($node3);
+        self::assertEquals(3, $node3->getAttribute('lft'));
+        self::assertEquals(8, $node3->getAttribute('rgt'));
 
         $result = $nodeToDelete->delete();
 
-        self::assertEquals(
-            1,
-            $result,
-            'Deleting the leaf node with ID \'4\' should affect exactly one row.',
-        );
-        self::assertNull(
-            Tree::findOne(4),
-            'Node with ID \'4\' should not exist after deletion.',
-        );
+        self::assertEquals(1, $result);
+        self::assertNull(Tree::findOne(4));
 
         $node5->refresh();
 
-        self::assertEquals(
-            4,
-            $node5->getAttribute('lft'),
-            'Node with ID \'5\' should have left value \'4\' after shifting.',
-        );
-        self::assertEquals(
-            5,
-            $node5->getAttribute('rgt'),
-            'Node with ID \'5\' should have right value \'5\' after shifting.',
-        );
+        self::assertEquals(4, $node5->getAttribute('lft'));
+        self::assertEquals(5, $node5->getAttribute('rgt'));
 
         $node6->refresh();
 
-        self::assertEquals(
-            7,
-            $node6->getAttribute('lft'),
-            'Node with ID \'6\' should have left value \'7\' after shifting.',
-        );
-        self::assertEquals(
-            12,
-            $node6->getAttribute('rgt'),
-            'Node with ID \'6\' should have right value \'12\' after shifting.',
-        );
+        self::assertEquals(7, $node6->getAttribute('lft'));
+        self::assertEquals(12, $node6->getAttribute('rgt'));
 
-        $node9->refresh();
+        $node3->refresh();
 
-        self::assertEquals(
-            14,
-            $node9->getAttribute('lft'),
-            'Node with ID \'9\' should have left value \'14\' after shifting.',
-        );
-        self::assertEquals(
-            27,
-            $node9->getAttribute('rgt'),
-            'Node with ID \'9\' should have right value \'27\' after shifting.',
-        );
+        self::assertEquals(3, $node3->getAttribute('lft'));
+        self::assertEquals(6, $node3->getAttribute('rgt'));
     }
 }

From d039c60ff3f2e4575e0e39017f0a4ead34e88c55 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 16:15:46 -0400
Subject: [PATCH 04/28] feat: Update mutation testing configuration and clean
 up JSON files.

---
 .github/workflows/mutation.yml | 3 +++
 composer.json                  | 2 +-
 infection.json5                | 3 +--
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index 0c66610..b3d7530 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -20,5 +20,8 @@ name: mutation test
 jobs:
   mutation:
     uses: php-forge/actions/.github/workflows/infection.yml@main
+    with:
+      command: phpstan-mutant-killer-infection-runner
+      composer-command: composer require --dev phpstan/mutant-killer-infection-runner
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}
diff --git a/composer.json b/composer.json
index 35d3f24..0f59fd4 100644
--- a/composer.json
+++ b/composer.json
@@ -9,13 +9,13 @@
         "behavior"
     ],
     "license": "BSD-3-Clause",
+    "minimum-stability": "dev",
     "require": {
         "php": ">=8.1",
         "yiisoft/yii2": "^2.0.53|^22"
     },
     "require-dev": {
         "ext-simplexml": "*",
-        "infection/infection": "^0.27|^0.29",
         "maglnet/composer-require-checker": "^4.1",
         "phpstan/extension-installer": "^1.4",
         "phpstan/phpstan-strict-rules": "^2.0.3",
diff --git a/infection.json5 b/infection.json5
index b47e1f0..d6406fa 100644
--- a/infection.json5
+++ b/infection.json5
@@ -10,6 +10,5 @@
         "directories": [
             "src"
         ]
-    },
-    "timeout": 45
+    }
 }

From fd62276e2ed87b7e117a1e76a43b9fe722886ce0 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 16:41:51 -0400
Subject: [PATCH 05/28] feat: Update mutation testing configuration and remove
 minimum stability requirement from `composer.json`.

---
 .github/workflows/mutation.yml | 4 ++--
 composer.json                  | 1 -
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index b3d7530..c7ade8a 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -21,7 +21,7 @@ jobs:
   mutation:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
-      command: phpstan-mutant-killer-infection-runner
-      composer-command: composer require --dev phpstan/mutant-killer-infection-runner
+      command-options: --static-analysis-tool=phpstan --threads=2 --ignore-msi-with-no-mutations --only-covered
+      composer-command: composer require --dev infection/infection:dev-master
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}
diff --git a/composer.json b/composer.json
index 0f59fd4..03dfc90 100644
--- a/composer.json
+++ b/composer.json
@@ -9,7 +9,6 @@
         "behavior"
     ],
     "license": "BSD-3-Clause",
-    "minimum-stability": "dev",
     "require": {
         "php": ">=8.1",
         "yiisoft/yii2": "^2.0.53|^22"

From d885491c2d460c7099e0746f689d4d44dbbe83ad Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 16:51:29 -0400
Subject: [PATCH 06/28] test: Enhance deletion tests for tree nodes and verify
 attribute shifts.

---
 tests/NestedSetsBehaviorTest.php | 119 +++++++++++++++++++++++++------
 1 file changed, 97 insertions(+), 22 deletions(-)

diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index c45d324..d9beec7 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1627,47 +1627,122 @@ public function testAfterDeleteShiftsLeftRightAttributesCorrectly(): void
 
         $nodeToDelete = Tree::findOne(4);
 
-        self::assertNotNull($nodeToDelete);
-        self::assertTrue($nodeToDelete->isLeaf());
-        self::assertEquals(4, $nodeToDelete->getAttribute('lft'));
-        self::assertEquals(5, $nodeToDelete->getAttribute('rgt'));
+        self::assertNotNull($nodeToDelete, 'Node 4 should exist for deletion test');
+        self::assertTrue($nodeToDelete->isLeaf(), 'Node 4 should be a leaf node');
+        self::assertEquals(4, $nodeToDelete->getAttribute('lft'), 'Node 4 should have lft=4');
+        self::assertEquals(5, $nodeToDelete->getAttribute('rgt'), 'Node 4 should have rgt=5');
 
         $node5 = Tree::findOne(5);
+        $node6 = Tree::findOne(6);
+        $node3 = Tree::findOne(3);
 
         self::assertNotNull($node5);
+        self::assertNotNull($node6);
+        self::assertNotNull($node3);
+
         self::assertEquals(6, $node5->getAttribute('lft'));
         self::assertEquals(7, $node5->getAttribute('rgt'));
-
-        $node6 = Tree::findOne(6);
-
-        self::assertNotNull($node6);
         self::assertEquals(9, $node6->getAttribute('lft'));
         self::assertEquals(14, $node6->getAttribute('rgt'));
-
-        $node3 = Tree::findOne(3);
-
-        self::assertNotNull($node3);
         self::assertEquals(3, $node3->getAttribute('lft'));
         self::assertEquals(8, $node3->getAttribute('rgt'));
 
         $result = $nodeToDelete->delete();
+        self::assertEquals(1, $result, 'Delete should affect exactly 1 row');
 
-        self::assertEquals(1, $result);
-        self::assertNull(Tree::findOne(4));
+        self::assertNull(Tree::findOne(4), 'Node 4 should no longer exist');
 
         $node5->refresh();
+        $node6->refresh();
+        $node3->refresh();
 
-        self::assertEquals(4, $node5->getAttribute('lft'));
-        self::assertEquals(5, $node5->getAttribute('rgt'));
+        self::assertEquals(4, $node5->getAttribute('lft'), 'Node 5 left should shift from 6 to 4');
+        self::assertEquals(5, $node5->getAttribute('rgt'), 'Node 5 right should shift from 7 to 5');
 
-        $node6->refresh();
+        self::assertEquals(7, $node6->getAttribute('lft'), 'Node 6 left should shift from 9 to 7');
+        self::assertEquals(12, $node6->getAttribute('rgt'), 'Node 6 right should shift from 14 to 12');
 
-        self::assertEquals(7, $node6->getAttribute('lft'));
-        self::assertEquals(12, $node6->getAttribute('rgt'));
+        self::assertEquals(3, $node3->getAttribute('lft'), 'Node 3 left should remain 3');
+        self::assertEquals(6, $node3->getAttribute('rgt'), 'Node 3 right should shift from 8 to 6');
+    }
 
-        $node3->refresh();
+    public function testAfterDeleteShiftStartsAtCorrectPosition(): void
+    {
+        $this->generateFixtureTree();
 
-        self::assertEquals(3, $node3->getAttribute('lft'));
-        self::assertEquals(6, $node3->getAttribute('rgt'));
+        $nodeToDelete = Tree::findOne(11);
+
+        self::assertNotNull($nodeToDelete);
+        self::assertEquals(18, $nodeToDelete->getAttribute('lft'));
+        self::assertEquals(19, $nodeToDelete->getAttribute('rgt'));
+
+        $node12 = Tree::findOne(12);
+        $node10 = Tree::findOne(10);
+        $node13 = Tree::findOne(13);
+
+        self::assertNotNull($node12);
+        self::assertNotNull($node10);
+        self::assertNotNull($node13);
+
+        self::assertEquals(20, $node12->getAttribute('lft'), 'Node 12 should start at 20');
+        self::assertEquals(21, $node12->getAttribute('rgt'), 'Node 12 should end at 21');
+        self::assertEquals(17, $node10->getAttribute('lft'), 'Node 10 should start at 17');
+        self::assertEquals(22, $node10->getAttribute('rgt'), 'Node 10 should end at 22');
+        self::assertEquals(23, $node13->getAttribute('lft'), 'Node 13 should start at 23');
+        self::assertEquals(28, $node13->getAttribute('rgt'), 'Node 13 should end at 28');
+
+        $result = $nodeToDelete->delete();
+        self::assertEquals(1, $result);
+        self::assertNull(Tree::findOne(11), 'Node 11 should be deleted');
+
+        $node12->refresh();
+        $node10->refresh();
+        $node13->refresh();
+
+        self::assertEquals(18, $node12->getAttribute('lft'), 'Node 12 left should shift from 20 to 18');
+        self::assertEquals(19, $node12->getAttribute('rgt'), 'Node 12 right should shift from 21 to 19');
+        self::assertEquals(17, $node10->getAttribute('lft'), 'Node 10 left should remain 17');
+        self::assertEquals(20, $node10->getAttribute('rgt'), 'Node 10 right should shift from 22 to 20');
+        self::assertEquals(21, $node13->getAttribute('lft'), 'Node 13 left should shift from 23 to 21');
+        self::assertEquals(26, $node13->getAttribute('rgt'), 'Node 13 right should shift from 28 to 26');
+        self::assertLessThan(
+            $node10->getAttribute('rgt'),
+            $node12->getAttribute('rgt'),
+            'Child node 12 must be contained within parent node 10'
+        );
+        self::assertGreaterThan(
+            $node10->getAttribute('lft'),
+            $node12->getAttribute('lft'),
+            'Child node 12 must be contained within parent node 10'
+        );
+    }
+
+    public function testDeleteWithChildrenShiftsCorrectly(): void
+    {
+        $this->generateFixtureTree();
+
+        $nodeToDelete = Tree::findOne(3);
+
+        self::assertNotNull($nodeToDelete);
+        self::assertEquals(3, $nodeToDelete->getAttribute('lft'));
+        self::assertEquals(8, $nodeToDelete->getAttribute('rgt'));
+
+        $node6 = Tree::findOne(6);
+
+        self::assertNotNull($node6);
+        self::assertEquals(9, $node6->getAttribute('lft'));
+        self::assertEquals(14, $node6->getAttribute('rgt'));
+
+        $result = $nodeToDelete->deleteWithChildren();
+
+        self::assertEquals(3, $result);
+        self::assertNull(Tree::findOne(3));
+        self::assertNull(Tree::findOne(4));
+        self::assertNull(Tree::findOne(5));
+
+        $node6->refresh();
+
+        self::assertEquals(3, $node6->getAttribute('lft'));
+        self::assertEquals(8, $node6->getAttribute('rgt'));
     }
 }

From d6d891ba1358923376f19392b7ce78c60e8d9b45 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 16:58:25 -0400
Subject: [PATCH 07/28] feat: Update mutation testing workflow to include
 static analysis command.

---
 .github/workflows/mutation.yml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index c7ade8a..9ff3b73 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -22,6 +22,8 @@ jobs:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
       command-options: --static-analysis-tool=phpstan --threads=2 --ignore-msi-with-no-mutations --only-covered
-      composer-command: composer require --dev infection/infection:dev-master
+      composer-command: |
+        composer require --dev infection/infection:dev-master
+        vendor/bin/phpstan --configuration=phpstan.neon analyse
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}

From daf60d726ca8afba4cb19802a642512b1f7023df Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 17:01:44 -0400
Subject: [PATCH 08/28] fix: Simplify composer command in mutation testing
 workflow.

---
 .github/workflows/mutation.yml | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index 9ff3b73..d08baea 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -22,8 +22,6 @@ jobs:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
       command-options: --static-analysis-tool=phpstan --threads=2 --ignore-msi-with-no-mutations --only-covered
-      composer-command: |
-        composer require --dev infection/infection:dev-master
-        vendor/bin/phpstan --configuration=phpstan.neon analyse
+      composer-command: composer require --dev infection/infection:dev-master && vendor/bin/phpstan --configuration=phpstan.neon analyse
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}

From e6af6b2198a757605b6f25f2014b5cc216c30411 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 17:22:29 -0400
Subject: [PATCH 09/28] feat: Add phpStan configuration to `infection.json5`.

---
 infection.json5 | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/infection.json5 b/infection.json5
index d6406fa..15361d9 100644
--- a/infection.json5
+++ b/infection.json5
@@ -10,5 +10,8 @@
         "directories": [
             "src"
         ]
-    }
+    },
+    "phpStan": {
+        "configDir": "."
+    },
 }

From 6c1c41a6c1d9b32d7b444c210c9a280ec1f23382 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 17:29:10 -0400
Subject: [PATCH 10/28] feat: Add log verbosity option to mutation testing
 command.

---
 .github/workflows/mutation.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index d08baea..1741a2a 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -21,7 +21,7 @@ jobs:
   mutation:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
-      command-options: --static-analysis-tool=phpstan --threads=2 --ignore-msi-with-no-mutations --only-covered
+      command-options: --static-analysis-tool=phpstan --threads=2 --ignore-msi-with-no-mutations --only-covered --log-verbosity=all
       composer-command: composer require --dev infection/infection:dev-master && vendor/bin/phpstan --configuration=phpstan.neon analyse
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}

From af317f9f0b80026dbb96cf2249caa84a0d8174a9 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 17:45:55 -0400
Subject: [PATCH 11/28] test: Refactor deletion tests to improve clarity and
 accuracy of node attribute shifts.

---
 tests/NestedSetsBehaviorTest.php | 211 +++++++++++++++----------------
 1 file changed, 101 insertions(+), 110 deletions(-)

diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index d9beec7..8fc6682 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1621,128 +1621,119 @@ public function makeRoot(): bool
         $node->makeRoot();
     }
 
-    public function testAfterDeleteShiftsLeftRightAttributesCorrectly(): void
+    public function testDeleteNodeDoesNotAffectNodeWithLeftEqualToDeletedRight(): void
     {
-        $this->generateFixtureTree();
-
-        $nodeToDelete = Tree::findOne(4);
-
-        self::assertNotNull($nodeToDelete, 'Node 4 should exist for deletion test');
-        self::assertTrue($nodeToDelete->isLeaf(), 'Node 4 should be a leaf node');
-        self::assertEquals(4, $nodeToDelete->getAttribute('lft'), 'Node 4 should have lft=4');
-        self::assertEquals(5, $nodeToDelete->getAttribute('rgt'), 'Node 4 should have rgt=5');
-
-        $node5 = Tree::findOne(5);
-        $node6 = Tree::findOne(6);
-        $node3 = Tree::findOne(3);
-
-        self::assertNotNull($node5);
-        self::assertNotNull($node6);
-        self::assertNotNull($node3);
-
-        self::assertEquals(6, $node5->getAttribute('lft'));
-        self::assertEquals(7, $node5->getAttribute('rgt'));
-        self::assertEquals(9, $node6->getAttribute('lft'));
-        self::assertEquals(14, $node6->getAttribute('rgt'));
-        self::assertEquals(3, $node3->getAttribute('lft'));
-        self::assertEquals(8, $node3->getAttribute('rgt'));
-
-        $result = $nodeToDelete->delete();
-        self::assertEquals(1, $result, 'Delete should affect exactly 1 row');
-
-        self::assertNull(Tree::findOne(4), 'Node 4 should no longer exist');
-
-        $node5->refresh();
-        $node6->refresh();
-        $node3->refresh();
-
-        self::assertEquals(4, $node5->getAttribute('lft'), 'Node 5 left should shift from 6 to 4');
-        self::assertEquals(5, $node5->getAttribute('rgt'), 'Node 5 right should shift from 7 to 5');
-
-        self::assertEquals(7, $node6->getAttribute('lft'), 'Node 6 left should shift from 9 to 7');
-        self::assertEquals(12, $node6->getAttribute('rgt'), 'Node 6 right should shift from 14 to 12');
+        $this->createDatabase();
 
-        self::assertEquals(3, $node3->getAttribute('lft'), 'Node 3 left should remain 3');
-        self::assertEquals(6, $node3->getAttribute('rgt'), 'Node 3 right should shift from 8 to 6');
+        $root = new Tree(['name' => 'Root']);
+        $root->makeRoot();
+
+        $node1 = new Tree(['name' => 'Node1']);
+        $node1->appendTo($root);
+
+        $child1 = new Tree(['name' => 'Child1']);
+        $child1->appendTo($node1);
+
+        $node2 = new Tree(['name' => 'Node2']);
+        $node2->appendTo($root);
+
+        $child2 = new Tree(['name' => 'Child2']);
+        $child2->appendTo($node2);
+
+        $root->refresh();
+        $node1->refresh();
+        $child1->refresh();
+        $node2->refresh();
+        $child2->refresh();
+
+        self::assertEquals(1, $root->lft);
+        self::assertEquals(10, $root->rgt);
+        self::assertEquals(2, $node1->lft);
+        self::assertEquals(5, $node1->rgt);
+        self::assertEquals(3, $child1->lft);
+        self::assertEquals(4, $child1->rgt);
+        self::assertEquals(6, $node2->lft);
+        self::assertEquals(9, $node2->rgt);
+        self::assertEquals(7, $child2->lft);
+        self::assertEquals(8, $child2->rgt);
+
+        $node1->deleteWithChildren();
+
+        $root->refresh();
+        $node2->refresh();
+        $child2->refresh();
+
+        self::assertEquals(1, $root->lft);
+        self::assertEquals(6, $root->rgt);
+        self::assertEquals(2, $node2->lft);
+        self::assertEquals(5, $node2->rgt);
+        self::assertEquals(3, $child2->lft);
+        self::assertEquals(4, $child2->rgt);
     }
 
-    public function testAfterDeleteShiftStartsAtCorrectPosition(): void
+    public function testShiftBehaviorAfterDeleteWithPreciseBoundary(): void
     {
-        $this->generateFixtureTree();
-
-        $nodeToDelete = Tree::findOne(11);
-
-        self::assertNotNull($nodeToDelete);
-        self::assertEquals(18, $nodeToDelete->getAttribute('lft'));
-        self::assertEquals(19, $nodeToDelete->getAttribute('rgt'));
-
-        $node12 = Tree::findOne(12);
-        $node10 = Tree::findOne(10);
-        $node13 = Tree::findOne(13);
-
-        self::assertNotNull($node12);
-        self::assertNotNull($node10);
-        self::assertNotNull($node13);
-
-        self::assertEquals(20, $node12->getAttribute('lft'), 'Node 12 should start at 20');
-        self::assertEquals(21, $node12->getAttribute('rgt'), 'Node 12 should end at 21');
-        self::assertEquals(17, $node10->getAttribute('lft'), 'Node 10 should start at 17');
-        self::assertEquals(22, $node10->getAttribute('rgt'), 'Node 10 should end at 22');
-        self::assertEquals(23, $node13->getAttribute('lft'), 'Node 13 should start at 23');
-        self::assertEquals(28, $node13->getAttribute('rgt'), 'Node 13 should end at 28');
-
-        $result = $nodeToDelete->delete();
-        self::assertEquals(1, $result);
-        self::assertNull(Tree::findOne(11), 'Node 11 should be deleted');
-
-        $node12->refresh();
-        $node10->refresh();
-        $node13->refresh();
-
-        self::assertEquals(18, $node12->getAttribute('lft'), 'Node 12 left should shift from 20 to 18');
-        self::assertEquals(19, $node12->getAttribute('rgt'), 'Node 12 right should shift from 21 to 19');
-        self::assertEquals(17, $node10->getAttribute('lft'), 'Node 10 left should remain 17');
-        self::assertEquals(20, $node10->getAttribute('rgt'), 'Node 10 right should shift from 22 to 20');
-        self::assertEquals(21, $node13->getAttribute('lft'), 'Node 13 left should shift from 23 to 21');
-        self::assertEquals(26, $node13->getAttribute('rgt'), 'Node 13 right should shift from 28 to 26');
-        self::assertLessThan(
-            $node10->getAttribute('rgt'),
-            $node12->getAttribute('rgt'),
-            'Child node 12 must be contained within parent node 10'
-        );
-        self::assertGreaterThan(
-            $node10->getAttribute('lft'),
-            $node12->getAttribute('lft'),
-            'Child node 12 must be contained within parent node 10'
-        );
-    }
-
-    public function testDeleteWithChildrenShiftsCorrectly(): void
-    {
-        $this->generateFixtureTree();
+        $this->createDatabase();
 
-        $nodeToDelete = Tree::findOne(3);
+        $root = new Tree(['name' => 'Root']);
+        $root->makeRoot();
 
-        self::assertNotNull($nodeToDelete);
-        self::assertEquals(3, $nodeToDelete->getAttribute('lft'));
-        self::assertEquals(8, $nodeToDelete->getAttribute('rgt'));
+        $nodes = [];
 
-        $node6 = Tree::findOne(6);
+        for ($i = 1; $i <= 5; $i++) {
+            $nodes[$i] = new Tree(['name' => "Node$i"]);
+            // @phpstan-ignore-next-line
+            $nodes[$i]->appendTo($root);
+        }
 
-        self::assertNotNull($node6);
-        self::assertEquals(9, $node6->getAttribute('lft'));
-        self::assertEquals(14, $node6->getAttribute('rgt'));
+        foreach ($nodes as $node) {
+            $node->refresh();
+        }
 
-        $result = $nodeToDelete->deleteWithChildren();
+        $root->refresh();
 
-        self::assertEquals(3, $result);
-        self::assertNull(Tree::findOne(3));
-        self::assertNull(Tree::findOne(4));
-        self::assertNull(Tree::findOne(5));
+        // @phpstan-ignore-next-line
+        $nodeToDelete = $nodes[2];
+        $rightValueBeforeDelete = $nodeToDelete->rgt;
 
-        $node6->refresh();
+        $valuesBeforeDelete = [];
 
-        self::assertEquals(3, $node6->getAttribute('lft'));
-        self::assertEquals(8, $node6->getAttribute('rgt'));
+        foreach ($nodes as $i => $node) {
+            if ($i !== 2) {
+                $valuesBeforeDelete[$i] = [
+                    'lft' => $node->lft,
+                    'rgt' => $node->rgt
+                ];
+            }
+        }
+
+        $nodeToDelete->delete();
+
+        foreach ($nodes as $i => $node) {
+            if ($i !== 2) {
+                $node->refresh();
+
+                // @phpstan-ignore-next-line
+                $oldLft = $valuesBeforeDelete[$i]['lft'];
+                // @phpstan-ignore-next-line
+                $oldRgt = $valuesBeforeDelete[$i]['rgt'];
+
+                if ($oldLft > $rightValueBeforeDelete) {
+                    self::assertEquals($oldLft - 2, $node->lft,
+                        "Node $i left should be shifted when > deleted right");
+                } else {
+                    self::assertEquals($oldLft, $node->lft,
+                        "Node $i left should NOT be shifted when <= deleted right");
+                }
+
+                if ($oldRgt > $rightValueBeforeDelete) {
+                    self::assertEquals($oldRgt - 2, $node->rgt,
+                        "Node $i right should be shifted when > deleted right");
+                } else {
+                    self::assertEquals($oldRgt, $node->rgt,
+                        "Node $i right should NOT be shifted when <= deleted right");
+                }
+            }
+        }
     }
 }

From 139b336554caaa6a09fb9a14a505c0aaf40b53f4 Mon Sep 17 00:00:00 2001
From: StyleCI Bot <bot@styleci.io>
Date: Sat, 28 Jun 2025 21:46:18 +0000
Subject: [PATCH 12/28] Apply fixes from StyleCI

---
 tests/NestedSetsBehaviorTest.php | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index 8fc6682..bf44eb0 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1702,7 +1702,7 @@ public function testShiftBehaviorAfterDeleteWithPreciseBoundary(): void
             if ($i !== 2) {
                 $valuesBeforeDelete[$i] = [
                     'lft' => $node->lft,
-                    'rgt' => $node->rgt
+                    'rgt' => $node->rgt,
                 ];
             }
         }
@@ -1719,19 +1719,31 @@ public function testShiftBehaviorAfterDeleteWithPreciseBoundary(): void
                 $oldRgt = $valuesBeforeDelete[$i]['rgt'];
 
                 if ($oldLft > $rightValueBeforeDelete) {
-                    self::assertEquals($oldLft - 2, $node->lft,
-                        "Node $i left should be shifted when > deleted right");
+                    self::assertEquals(
+                        $oldLft - 2,
+                        $node->lft,
+                        "Node $i left should be shifted when > deleted right"
+                    );
                 } else {
-                    self::assertEquals($oldLft, $node->lft,
-                        "Node $i left should NOT be shifted when <= deleted right");
+                    self::assertEquals(
+                        $oldLft,
+                        $node->lft,
+                        "Node $i left should NOT be shifted when <= deleted right"
+                    );
                 }
 
                 if ($oldRgt > $rightValueBeforeDelete) {
-                    self::assertEquals($oldRgt - 2, $node->rgt,
-                        "Node $i right should be shifted when > deleted right");
+                    self::assertEquals(
+                        $oldRgt - 2,
+                        $node->rgt,
+                        "Node $i right should be shifted when > deleted right"
+                    );
                 } else {
-                    self::assertEquals($oldRgt, $node->rgt,
-                        "Node $i right should NOT be shifted when <= deleted right");
+                    self::assertEquals(
+                        $oldRgt,
+                        $node->rgt,
+                        "Node $i right should NOT be shifted when <= deleted right"
+                    );
                 }
             }
         }

From 1f7d3a217379cb930142be993dac2d565a422b00 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 17:56:19 -0400
Subject: [PATCH 13/28] fix: Correct left-right attribute shifting logic in
 `NestedSetsBehavior`.

---
 src/NestedSetsBehavior.php       | 2 +-
 tests/NestedSetsBehaviorTest.php | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index fd25857..8536d4c 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -142,7 +142,7 @@ public function afterDelete(): void
         $rightValue = $this->getOwner()->getAttribute($this->rightAttribute);
 
         if ($this->operation === self::OPERATION_DELETE_WITH_CHILDREN || $this->getOwner()->isLeaf()) {
-            $this->shiftLeftRightAttribute($rightValue + 1, $leftValue - $rightValue - 1);
+            $this->shiftLeftRightAttribute($rightValue, $leftValue - $rightValue - 1);
         } else {
             $condition = [
                 'and',
diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index bf44eb0..4904159 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1722,13 +1722,13 @@ public function testShiftBehaviorAfterDeleteWithPreciseBoundary(): void
                     self::assertEquals(
                         $oldLft - 2,
                         $node->lft,
-                        "Node $i left should be shifted when > deleted right"
+                        "Node $i left should be shifted when > deleted right",
                     );
                 } else {
                     self::assertEquals(
                         $oldLft,
                         $node->lft,
-                        "Node $i left should NOT be shifted when <= deleted right"
+                        "Node $i left should NOT be shifted when <= deleted right",
                     );
                 }
 
@@ -1736,13 +1736,13 @@ public function testShiftBehaviorAfterDeleteWithPreciseBoundary(): void
                     self::assertEquals(
                         $oldRgt - 2,
                         $node->rgt,
-                        "Node $i right should be shifted when > deleted right"
+                        "Node $i right should be shifted when > deleted right",
                     );
                 } else {
                     self::assertEquals(
                         $oldRgt,
                         $node->rgt,
-                        "Node $i right should NOT be shifted when <= deleted right"
+                        "Node $i right should NOT be shifted when <= deleted right",
                     );
                 }
             }

From 7e15a5601694a8d14766c1b9447a032d87037400 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 18:02:35 -0400
Subject: [PATCH 14/28] fix: Adjust left-right attribute shifting logic in
 `NestedSetsBehavior`.

---
 .github/workflows/mutation.yml | 2 +-
 src/NestedSetsBehavior.php     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index 1741a2a..d08baea 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -21,7 +21,7 @@ jobs:
   mutation:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
-      command-options: --static-analysis-tool=phpstan --threads=2 --ignore-msi-with-no-mutations --only-covered --log-verbosity=all
+      command-options: --static-analysis-tool=phpstan --threads=2 --ignore-msi-with-no-mutations --only-covered
       composer-command: composer require --dev infection/infection:dev-master && vendor/bin/phpstan --configuration=phpstan.neon analyse
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}
diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index 8536d4c..fea406f 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -174,7 +174,7 @@ public function afterDelete(): void
                 ],
                 $condition,
             );
-            $this->shiftLeftRightAttribute($rightValue + 1, -2);
+            $this->shiftLeftRightAttribute($rightValue, -2);
         }
 
         $this->operation = null;

From 1ce4a5bd5bfef6aed0c30a17c2b4e50958f48230 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 18:12:32 -0400
Subject: [PATCH 15/28] fix: Improve null handling for left-right attribute
 values in `afterUpdate` method.

---
 src/NestedSetsBehavior.php | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index fea406f..15ab213 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -247,15 +247,15 @@ public function afterInsert(): void
      */
     public function afterUpdate(): void
     {
-        $nodeLeftValue = $this->node?->getAttribute($this->leftAttribute) ?? 0;
-        $nodeRightValue = $this->node?->getAttribute($this->rightAttribute) ?? 0;
+        $nodeLeftValue = $this->node?->getAttribute($this->leftAttribute);
+        $nodeRightValue = $this->node?->getAttribute($this->rightAttribute);
 
         match ($this->operation) {
-            self::OPERATION_APPEND_TO => $this->moveNode($nodeRightValue, 1),
-            self::OPERATION_INSERT_AFTER => $this->moveNode($nodeRightValue + 1, 0),
-            self::OPERATION_INSERT_BEFORE => $this->moveNode($nodeLeftValue, 0),
+            self::OPERATION_APPEND_TO => $nodeRightValue !== null ? $this->moveNode($nodeRightValue, 1) : null,
+            self::OPERATION_INSERT_AFTER => $nodeRightValue !== null ? $this->moveNode($nodeRightValue + 1, 0) : null,
+            self::OPERATION_INSERT_BEFORE => $nodeLeftValue !== null ? $this->moveNode($nodeLeftValue, 0) : null,
             self::OPERATION_MAKE_ROOT => $this->moveNodeAsRoot(),
-            self::OPERATION_PREPEND_TO => $this->moveNode($nodeLeftValue + 1, 1),
+            self::OPERATION_PREPEND_TO => $nodeLeftValue !== null ? $this->moveNode($nodeLeftValue + 1, 1) : null,
             default => null,
         };
 

From d1b8234cce15f0af90638488fdc26caad96dd807 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 19:34:30 -0400
Subject: [PATCH 16/28] refactor: Simplify node movement logic in
 `afterUpdate()` and `beforeInsert()` methods.

---
 src/NestedSetsBehavior.php       |  86 +++++++++++++--------
 tests/NestedSetsBehaviorTest.php | 128 -------------------------------
 2 files changed, 52 insertions(+), 162 deletions(-)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index 15ab213..bd55ed3 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -247,17 +247,22 @@ public function afterInsert(): void
      */
     public function afterUpdate(): void
     {
-        $nodeLeftValue = $this->node?->getAttribute($this->leftAttribute);
-        $nodeRightValue = $this->node?->getAttribute($this->rightAttribute);
-
-        match ($this->operation) {
-            self::OPERATION_APPEND_TO => $nodeRightValue !== null ? $this->moveNode($nodeRightValue, 1) : null,
-            self::OPERATION_INSERT_AFTER => $nodeRightValue !== null ? $this->moveNode($nodeRightValue + 1, 0) : null,
-            self::OPERATION_INSERT_BEFORE => $nodeLeftValue !== null ? $this->moveNode($nodeLeftValue, 0) : null,
-            self::OPERATION_MAKE_ROOT => $this->moveNodeAsRoot(),
-            self::OPERATION_PREPEND_TO => $nodeLeftValue !== null ? $this->moveNode($nodeLeftValue + 1, 1) : null,
-            default => null,
-        };
+        switch (true) {
+            case $this->operation === self::OPERATION_MAKE_ROOT:
+                $this->moveNodeAsRoot();
+                break;
+            case $this->operation === self::OPERATION_APPEND_TO && $this->node !== null:
+                $this->moveNode($this->node, $this->node->getAttribute($this->rightAttribute), 1);
+                break;
+            case $this->operation === self::OPERATION_INSERT_AFTER && $this->node !== null:
+                $this->moveNode($this->node, $this->node->getAttribute($this->rightAttribute) + 1, 0);
+                break;
+            case $this->operation === self::OPERATION_INSERT_BEFORE && $this->node !== null:
+                $this->moveNode($this->node, $this->node->getAttribute($this->leftAttribute), 0);
+                break;
+            case $this->operation === self::OPERATION_PREPEND_TO && $this->node !== null:
+                $this->moveNode($this->node, $this->node->getAttribute($this->leftAttribute) + 1, 1);
+        }
 
         $this->operation = null;
         $this->node = null;
@@ -361,23 +366,30 @@ public function beforeDelete(): void
      */
     public function beforeInsert(): void
     {
-        if ($this->node?->getIsNewRecord() === false) {
+        if ($this->node !== null && $this->node->getIsNewRecord() === false) {
             $this->node->refresh();
         }
 
-        $nodeLeftValue = $this->node?->getAttribute($this->leftAttribute) ?? 0;
-        $nodeRightValue = $this->node?->getAttribute($this->rightAttribute) ?? 0;
-
-        match ($this->operation) {
-            self::OPERATION_APPEND_TO => $this->beforeInsertNode($nodeRightValue, 1),
-            self::OPERATION_INSERT_AFTER => $this->beforeInsertNode($nodeRightValue + 1, 0),
-            self::OPERATION_INSERT_BEFORE => $this->beforeInsertNode($nodeLeftValue, 0),
-            self::OPERATION_MAKE_ROOT => $this->beforeInsertRootNode(),
-            self::OPERATION_PREPEND_TO => $this->beforeInsertNode($nodeLeftValue + 1, 1),
-            default => throw new NotSupportedException(
-                'Method "' . get_class($this->getOwner()) . '::insert" is not supported for inserting new nodes.',
-            ),
-        };
+        switch (true) {
+            case $this->operation === self::OPERATION_MAKE_ROOT:
+                $this->beforeInsertRootNode();
+                break;
+            case $this->operation === self::OPERATION_PREPEND_TO && $this->node !== null:
+                $this->beforeInsertNode($this->node->getAttribute($this->leftAttribute) + 1, 1);
+                break;
+            case $this->operation === self::OPERATION_INSERT_AFTER && $this->node !== null:
+                $this->beforeInsertNode($this->node->getAttribute($this->rightAttribute) + 1, 0);
+                break;
+            case $this->operation === self::OPERATION_INSERT_BEFORE && $this->node !== null:
+                $this->beforeInsertNode($this->node->getAttribute($this->leftAttribute), 0);
+                break;
+            case $this->operation === self::OPERATION_APPEND_TO && $this->node !== null:
+                $this->beforeInsertNode($this->node->getAttribute($this->rightAttribute), 1);
+            default:
+                throw new NotSupportedException(
+                    'Method "' . get_class($this->getOwner()) . '::insert" is not supported for inserting new nodes.',
+                );
+        }
     }
 
     /**
@@ -1053,14 +1065,19 @@ protected function beforeInsertNode(int|null $value, int $depth): void
             $this->getOwner()->setAttribute($this->rightAttribute, $value + 1);
         }
 
-        $nodeDepthValue = $this->node?->getAttribute($this->depthAttribute) ?? 0;
-        $this->getOwner()->setAttribute($this->depthAttribute, $nodeDepthValue + $depth);
+        $nodeDepthValue = $this->node?->getAttribute($this->depthAttribute);
 
-        if ($this->treeAttribute !== false) {
-            $this->getOwner()->setAttribute($this->treeAttribute, $this->node?->getAttribute($this->treeAttribute));
+        if ($nodeDepthValue !== null) {
+            $this->getOwner()->setAttribute($this->depthAttribute, $nodeDepthValue + $depth);
         }
 
-        $this->shiftLeftRightAttribute($value ?? 0, 2);
+        if ($this->treeAttribute !== false && $this->node !== null) {
+            $this->getOwner()->setAttribute($this->treeAttribute, $this->node->getAttribute($this->treeAttribute));
+        }
+
+        if ($value !== null) {
+            $this->shiftLeftRightAttribute($value, 2);
+        }
     }
 
     /**
@@ -1150,23 +1167,24 @@ protected function deleteWithChildrenInternal(): bool|int
      * This method is called internally during node movement operations such as append, prepend, insert before/after,
      * and supports both root and non-root node moves.
      *
+     * @param ActiveRecord $node Node to be moved within the nested set tree.
      * @param int $value Left attribute value indicating the new position for the node.
      * @param int $depth Depth offset to apply to the node and its descendants after the move.
      */
-    protected function moveNode(int $value, int $depth): void
+    protected function moveNode(ActiveRecord $node, int $value, int $depth): void
     {
         $db = $this->getOwner()::getDb();
         $leftValue = $this->getOwner()->getAttribute($this->leftAttribute);
         $rightValue = $this->getOwner()->getAttribute($this->rightAttribute);
         $depthValue = $this->getOwner()->getAttribute($this->depthAttribute);
         $depthAttribute = $db->quoteColumnName($this->depthAttribute);
-        $nodeDepthValue = $this->node?->getAttribute($this->depthAttribute) ?? 0;
+        $nodeDepthValue = $node->getAttribute($this->depthAttribute);
 
         $depth = $nodeDepthValue - $depthValue + $depth;
 
         if (
             $this->treeAttribute === false ||
-            $this->getOwner()->getAttribute($this->treeAttribute) === $this->node?->getAttribute($this->treeAttribute)
+            $this->getOwner()->getAttribute($this->treeAttribute) === $node->getAttribute($this->treeAttribute)
         ) {
             $delta = $rightValue - $leftValue + 1;
 
@@ -1227,7 +1245,7 @@ protected function moveNode(int $value, int $depth): void
         } else {
             $leftAttribute = $db->quoteColumnName($this->leftAttribute);
             $rightAttribute = $db->quoteColumnName($this->rightAttribute);
-            $nodeRootValue = $this->node?->getAttribute($this->treeAttribute);
+            $nodeRootValue = $node->getAttribute($this->treeAttribute);
 
             foreach ([$this->leftAttribute, $this->rightAttribute] as $attribute) {
                 $this->getOwner()::updateAll(
diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index 4904159..d311816 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1620,132 +1620,4 @@ public function makeRoot(): bool
 
         $node->makeRoot();
     }
-
-    public function testDeleteNodeDoesNotAffectNodeWithLeftEqualToDeletedRight(): void
-    {
-        $this->createDatabase();
-
-        $root = new Tree(['name' => 'Root']);
-        $root->makeRoot();
-
-        $node1 = new Tree(['name' => 'Node1']);
-        $node1->appendTo($root);
-
-        $child1 = new Tree(['name' => 'Child1']);
-        $child1->appendTo($node1);
-
-        $node2 = new Tree(['name' => 'Node2']);
-        $node2->appendTo($root);
-
-        $child2 = new Tree(['name' => 'Child2']);
-        $child2->appendTo($node2);
-
-        $root->refresh();
-        $node1->refresh();
-        $child1->refresh();
-        $node2->refresh();
-        $child2->refresh();
-
-        self::assertEquals(1, $root->lft);
-        self::assertEquals(10, $root->rgt);
-        self::assertEquals(2, $node1->lft);
-        self::assertEquals(5, $node1->rgt);
-        self::assertEquals(3, $child1->lft);
-        self::assertEquals(4, $child1->rgt);
-        self::assertEquals(6, $node2->lft);
-        self::assertEquals(9, $node2->rgt);
-        self::assertEquals(7, $child2->lft);
-        self::assertEquals(8, $child2->rgt);
-
-        $node1->deleteWithChildren();
-
-        $root->refresh();
-        $node2->refresh();
-        $child2->refresh();
-
-        self::assertEquals(1, $root->lft);
-        self::assertEquals(6, $root->rgt);
-        self::assertEquals(2, $node2->lft);
-        self::assertEquals(5, $node2->rgt);
-        self::assertEquals(3, $child2->lft);
-        self::assertEquals(4, $child2->rgt);
-    }
-
-    public function testShiftBehaviorAfterDeleteWithPreciseBoundary(): void
-    {
-        $this->createDatabase();
-
-        $root = new Tree(['name' => 'Root']);
-        $root->makeRoot();
-
-        $nodes = [];
-
-        for ($i = 1; $i <= 5; $i++) {
-            $nodes[$i] = new Tree(['name' => "Node$i"]);
-            // @phpstan-ignore-next-line
-            $nodes[$i]->appendTo($root);
-        }
-
-        foreach ($nodes as $node) {
-            $node->refresh();
-        }
-
-        $root->refresh();
-
-        // @phpstan-ignore-next-line
-        $nodeToDelete = $nodes[2];
-        $rightValueBeforeDelete = $nodeToDelete->rgt;
-
-        $valuesBeforeDelete = [];
-
-        foreach ($nodes as $i => $node) {
-            if ($i !== 2) {
-                $valuesBeforeDelete[$i] = [
-                    'lft' => $node->lft,
-                    'rgt' => $node->rgt,
-                ];
-            }
-        }
-
-        $nodeToDelete->delete();
-
-        foreach ($nodes as $i => $node) {
-            if ($i !== 2) {
-                $node->refresh();
-
-                // @phpstan-ignore-next-line
-                $oldLft = $valuesBeforeDelete[$i]['lft'];
-                // @phpstan-ignore-next-line
-                $oldRgt = $valuesBeforeDelete[$i]['rgt'];
-
-                if ($oldLft > $rightValueBeforeDelete) {
-                    self::assertEquals(
-                        $oldLft - 2,
-                        $node->lft,
-                        "Node $i left should be shifted when > deleted right",
-                    );
-                } else {
-                    self::assertEquals(
-                        $oldLft,
-                        $node->lft,
-                        "Node $i left should NOT be shifted when <= deleted right",
-                    );
-                }
-
-                if ($oldRgt > $rightValueBeforeDelete) {
-                    self::assertEquals(
-                        $oldRgt - 2,
-                        $node->rgt,
-                        "Node $i right should be shifted when > deleted right",
-                    );
-                } else {
-                    self::assertEquals(
-                        $oldRgt,
-                        $node->rgt,
-                        "Node $i right should NOT be shifted when <= deleted right",
-                    );
-                }
-            }
-        }
-    }
 }

From 0f780ca89f23929e7ee0c13bccbb889d8ea3af85 Mon Sep 17 00:00:00 2001
From: StyleCI Bot <bot@styleci.io>
Date: Sat, 28 Jun 2025 23:34:59 +0000
Subject: [PATCH 17/28] Apply fixes from StyleCI

---
 src/NestedSetsBehavior.php | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index bd55ed3..d3bbcd1 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -385,6 +385,7 @@ public function beforeInsert(): void
                 break;
             case $this->operation === self::OPERATION_APPEND_TO && $this->node !== null:
                 $this->beforeInsertNode($this->node->getAttribute($this->rightAttribute), 1);
+                // no break
             default:
                 throw new NotSupportedException(
                     'Method "' . get_class($this->getOwner()) . '::insert" is not supported for inserting new nodes.',

From 176fc7667276db98ba1b1737690b7a6a438c14db Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 19:45:16 -0400
Subject: [PATCH 18/28] fix: Use nullsafe operator for node check in
 beforeInsert method and update appendTo/insertAfter calls in tests.

---
 src/NestedSetsBehavior.php       | 2 +-
 tests/NestedSetsBehaviorTest.php | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index d3bbcd1..a5d68f5 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -366,7 +366,7 @@ public function beforeDelete(): void
      */
     public function beforeInsert(): void
     {
-        if ($this->node !== null && $this->node->getIsNewRecord() === false) {
+        if ($this->node?->getIsNewRecord() === false) {
             $this->node->refresh();
         }
 
diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index d311816..aec8081 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -678,7 +678,7 @@ public function testThrowExceptionWhenAppendToTargetIsSame(): void
         $this->expectException(Exception::class);
         $this->expectExceptionMessage('Can not move a node when the target node is same.');
 
-        $node->appendTo($childOfNode);
+        $node->appendTo($childOfNode, false);
     }
 
     public function testThrowExceptionWhenAppendToTargetIsChild(): void
@@ -1073,7 +1073,7 @@ public function testThrowExceptionWhenInsertAfterTargetIsNewRecord(): void
         $this->expectException(Exception::class);
         $this->expectExceptionMessage('Can not move a node when the target node is new record.');
 
-        $node->insertAfter(new Tree());
+        $node->insertAfter(new Tree(), false);
     }
 
     public function testThrowExceptionWhenInsertAfterTargetIsSame(): void

From 623460c28a8309fd035a7e5383697d701007838c Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 19:57:19 -0400
Subject: [PATCH 19/28] fix: Remove unnecessary node refresh calls in
 beforeInsert and beforeUpdate methods.

---
 src/NestedSetsBehavior.php | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index a5d68f5..96a1259 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -331,8 +331,6 @@ public function beforeDelete(): void
                 'Method "' . get_class($this->getOwner()) . '::delete" is not supported for deleting root nodes.',
             );
         }
-
-        $this->getOwner()->refresh();
     }
 
     /**
@@ -366,10 +364,6 @@ public function beforeDelete(): void
      */
     public function beforeInsert(): void
     {
-        if ($this->node?->getIsNewRecord() === false) {
-            $this->node->refresh();
-        }
-
         switch (true) {
             case $this->operation === self::OPERATION_MAKE_ROOT:
                 $this->beforeInsertRootNode();
@@ -420,10 +414,6 @@ public function beforeInsert(): void
      */
     public function beforeUpdate(): void
     {
-        if ($this->node?->getIsNewRecord() === false) {
-            $this->node->refresh();
-        }
-
         switch ($this->operation) {
             case self::OPERATION_MAKE_ROOT:
                 if ($this->treeAttribute === false) {

From 68a3895805b02a0d22d7df1d0724d5d48fdd6723 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 20:03:57 -0400
Subject: [PATCH 20/28] fix: Correct left-right attribute shifting logic in
 `NestedSetsBehavior`.

---
 src/NestedSetsBehavior.php | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index 96a1259..e9feb6a 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -1232,7 +1232,7 @@ protected function moveNode(ActiveRecord $node, int $value, int $depth): void
                 );
             }
 
-            $this->shiftLeftRightAttribute($rightValue + 1, -$delta);
+            $this->shiftLeftRightAttribute($rightValue, -$delta);
         } else {
             $leftAttribute = $db->quoteColumnName($this->leftAttribute);
             $rightAttribute = $db->quoteColumnName($this->rightAttribute);
@@ -1285,7 +1285,7 @@ protected function moveNode(ActiveRecord $node, int $value, int $depth): void
                     ],
                 ],
             );
-            $this->shiftLeftRightAttribute($rightValue + 1, $leftValue - $rightValue - 1);
+            $this->shiftLeftRightAttribute($rightValue, $leftValue - $rightValue - 1);
         }
     }
 
@@ -1341,7 +1341,7 @@ protected function moveNodeAsRoot(): void
                 ],
             ],
         );
-        $this->shiftLeftRightAttribute($rightValue + 1, $leftValue - $rightValue - 1);
+        $this->shiftLeftRightAttribute($rightValue, $leftValue - $rightValue - 1);
     }
 
     /**

From 7a0b9c6a9d52724b18e0afa8c4c32cb0ba7d2afb Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 20:28:29 -0400
Subject: [PATCH 21/28] fix: Correct logic for appending nodes in
 `NestedSetsBehavior` and add test for appending to existing child node.

---
 src/NestedSetsBehavior.php            |  4 ++--
 tests/NestedSetsQueryBehaviorTest.php | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index e9feb6a..0c264b8 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -378,8 +378,8 @@ public function beforeInsert(): void
                 $this->beforeInsertNode($this->node->getAttribute($this->leftAttribute), 0);
                 break;
             case $this->operation === self::OPERATION_APPEND_TO && $this->node !== null:
-                $this->beforeInsertNode($this->node->getAttribute($this->rightAttribute), 1);
-                // no break
+                $this->beforeInsertNode($this->node->getAttribute($this->rightAttribute), 0);
+                break;
             default:
                 throw new NotSupportedException(
                     'Method "' . get_class($this->getOwner()) . '::insert" is not supported for inserting new nodes.',
diff --git a/tests/NestedSetsQueryBehaviorTest.php b/tests/NestedSetsQueryBehaviorTest.php
index abc9d84..ce986b6 100644
--- a/tests/NestedSetsQueryBehaviorTest.php
+++ b/tests/NestedSetsQueryBehaviorTest.php
@@ -70,4 +70,23 @@ public function testThrowLogicExceptionWhenBehaviorIsDetachedFromOwner(): void
 
         $behavior->leaves();
     }
+
+    public function testAppendNodeToExistingChildNode(): void
+    {
+        $this->generateFixtureTree();
+
+        $node = new Tree(['name' => 'New node']);
+
+        $childOfNode = Tree::findOne(2);
+
+        self::assertNotNull(
+            $childOfNode,
+            'Child node with ID \'2\' should exist before appending.'
+        );
+
+        self::assertTrue(
+            $node->appendTo($childOfNode),
+            'Appending a new node to the existing child node should return \'true\'.'
+        );
+    }
 }

From 053f00a0d985b9cedda9298d8738162cc6623854 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 20:44:58 -0400
Subject: [PATCH 22/28] test: Add tests for appending nodes to existing child
 nodes and verify depth behavior in `NestedSetsBehavior`.

---
 tests/NestedSetsBehaviorTest.php      | 148 ++++++++++++++++++++++++++
 tests/NestedSetsQueryBehaviorTest.php |  19 ----
 2 files changed, 148 insertions(+), 19 deletions(-)

diff --git a/tests/NestedSetsBehaviorTest.php b/tests/NestedSetsBehaviorTest.php
index aec8081..8c469bf 100644
--- a/tests/NestedSetsBehaviorTest.php
+++ b/tests/NestedSetsBehaviorTest.php
@@ -1620,4 +1620,152 @@ public function makeRoot(): bool
 
         $node->makeRoot();
     }
+
+    public function testAppendNodeToExistingChildNode(): void
+    {
+        $this->generateFixtureTree();
+
+        $node = new Tree(['name' => 'New node']);
+
+        $childOfNode = Tree::findOne(2);
+
+        self::assertNotNull(
+            $childOfNode,
+            'Child node with ID \'2\' should exist before appending.',
+        );
+
+        self::assertTrue(
+            $node->appendTo($childOfNode),
+            'Appending a new node to the existing child node should return \'true\'.',
+        );
+    }
+
+    public function testAppendToSetsCorrectDepthForNewNode(): void
+    {
+        $this->createDatabase();
+
+        $root = new Tree(['name' => 'Root']);
+
+        $root->makeRoot();
+
+        $parent = new Tree(['name' => 'Parent']);
+
+        $parent->appendTo($root);
+
+        $parent->refresh();
+
+        self::assertEquals(1, $parent->depth);
+
+        $child = new Tree(['name' => 'Child']);
+
+        $child->appendTo($parent);
+
+        $child->refresh();
+
+        self::assertEquals(2, $child->depth);
+
+        $grandchild = new Tree(['name' => 'Grandchild']);
+
+        $grandchild->appendTo($child);
+        $grandchild->refresh();
+
+        self::assertEquals(3, $grandchild->depth);
+    }
+
+    public function testAppendToAndPrependToHaveSameDepthBehavior(): void
+    {
+        $this->createDatabase();
+
+        $root = new Tree(['name' => 'Root']);
+
+        $root->makeRoot();
+
+        $parent = new Tree(['name' => 'Parent']);
+
+        $parent->appendTo($root);
+
+        $child1 = new Tree(['name' => 'Child1']);
+
+        $child1->prependTo($parent);
+
+        $child2 = new Tree(['name' => 'Child2']);
+
+        $child2->appendTo($parent);
+
+        $child1->refresh();
+
+        self::assertEquals($child1->depth, $child2->depth);
+
+        $child2->refresh();
+
+        self::assertEquals(2, $child1->depth);
+    }
+
+    public function testAppendToSetsCorrectDepthForMultipleTree(): void
+    {
+        $this->createDatabase();
+
+        $root = new MultipleTree(['name' => 'Root']);
+
+        $root->makeRoot();
+
+        $level1 = new MultipleTree(['name' => 'Level1']);
+
+        $level1->appendTo($root);
+
+        $level2 = new MultipleTree(['name' => 'Level2']);
+
+        $level2->appendTo($level1);
+
+        $level3 = new MultipleTree(['name' => 'Level3']);
+
+        $level3->appendTo($level2);
+
+        $level1->refresh();
+
+        self::assertEquals(1, $level1->depth);
+
+        $level2->refresh();
+
+        self::assertEquals(2, $level2->depth);
+
+        $level3->refresh();
+
+        self::assertEquals(3, $level3->depth);
+    }
+
+    public function testDepthDiffersBetweenSiblingsAndChildren(): void
+    {
+        $this->createDatabase();
+
+        $root = new Tree(['name' => 'Root']);
+
+        $root->makeRoot();
+
+        $parent = new Tree(['name' => 'Parent']);
+
+        $parent->appendTo($root);
+
+        $sibling = new Tree(['name' => 'Sibling']);
+
+        $sibling->insertAfter($parent);
+
+        $child = new Tree(['name' => 'Child']);
+
+        $child->appendTo($parent);
+
+        $parent->refresh();
+
+        self::assertEquals($parent->depth, $sibling->depth);
+        self::assertEquals($parent->depth + 1, $child->depth);
+        self::assertEquals(1, $parent->depth);
+
+        $sibling->refresh();
+
+        self::assertEquals(1, $sibling->depth);
+
+        $child->refresh();
+
+        self::assertEquals(2, $child->depth);
+    }
 }
diff --git a/tests/NestedSetsQueryBehaviorTest.php b/tests/NestedSetsQueryBehaviorTest.php
index ce986b6..abc9d84 100644
--- a/tests/NestedSetsQueryBehaviorTest.php
+++ b/tests/NestedSetsQueryBehaviorTest.php
@@ -70,23 +70,4 @@ public function testThrowLogicExceptionWhenBehaviorIsDetachedFromOwner(): void
 
         $behavior->leaves();
     }
-
-    public function testAppendNodeToExistingChildNode(): void
-    {
-        $this->generateFixtureTree();
-
-        $node = new Tree(['name' => 'New node']);
-
-        $childOfNode = Tree::findOne(2);
-
-        self::assertNotNull(
-            $childOfNode,
-            'Child node with ID \'2\' should exist before appending.'
-        );
-
-        self::assertTrue(
-            $node->appendTo($childOfNode),
-            'Appending a new node to the existing child node should return \'true\'.'
-        );
-    }
 }

From 9c40d4bb7cc6c7b88ee3eb1dd6532b1f38210311 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sat, 28 Jun 2025 20:48:21 -0400
Subject: [PATCH 23/28] fix: Update right attribute handling in
 beforeInsertNode for appending nodes.

---
 src/NestedSetsBehavior.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/NestedSetsBehavior.php b/src/NestedSetsBehavior.php
index 0c264b8..a1fdd4b 100644
--- a/src/NestedSetsBehavior.php
+++ b/src/NestedSetsBehavior.php
@@ -378,7 +378,7 @@ public function beforeInsert(): void
                 $this->beforeInsertNode($this->node->getAttribute($this->leftAttribute), 0);
                 break;
             case $this->operation === self::OPERATION_APPEND_TO && $this->node !== null:
-                $this->beforeInsertNode($this->node->getAttribute($this->rightAttribute), 0);
+                $this->beforeInsertNode($this->node->getAttribute($this->rightAttribute), 1);
                 break;
             default:
                 throw new NotSupportedException(

From 0176e5e2720bb6e224bc17f6062e8bfa1ffe0e18 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sun, 29 Jun 2025 06:01:27 -0400
Subject: [PATCH 24/28] fix: Simplify mutation job configuration by removing
 unnecessary command options in `mutation.yml`.

---
 .github/workflows/mutation.yml | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index d08baea..9c6f1ec 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -21,7 +21,6 @@ jobs:
   mutation:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
-      command-options: --static-analysis-tool=phpstan --threads=2 --ignore-msi-with-no-mutations --only-covered
-      composer-command: composer require --dev infection/infection:dev-master && vendor/bin/phpstan --configuration=phpstan.neon analyse
+      phpstan: true
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}

From 49aac8af5745f870513b06e2e3df7817371fe55c Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sun, 29 Jun 2025 06:03:36 -0400
Subject: [PATCH 25/28] fix: Add tools configuration for infection in mutation
 job.

---
 .github/workflows/mutation.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index 9c6f1ec..d8fd3b8 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -22,5 +22,6 @@ jobs:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
       phpstan: true
+      tools: infection/infection:dev-master
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}

From 4786d28c9e8b1cb7863cc428eac7d406d9fe454b Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sun, 29 Jun 2025 06:22:08 -0400
Subject: [PATCH 26/28] fix: Remove unnecessary tools configuration from
 mutation job.

---
 .github/workflows/mutation.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index d8fd3b8..c95057f 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -21,7 +21,7 @@ jobs:
   mutation:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
+      development: true
       phpstan: true
-      tools: infection/infection:dev-master
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}

From 483e39e5eae14cc05b565bd4ffcec80a23735ef9 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sun, 29 Jun 2025 06:24:03 -0400
Subject: [PATCH 27/28] fix: Correct typo in development configuration for
 mutation job.

---
 .github/workflows/mutation.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index c95057f..e2dcd58 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -21,7 +21,7 @@ jobs:
   mutation:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
-      development: true
+      devolopment: true
       phpstan: true
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}

From e731f47c57b15120e34c4e712d1ddacd3079f957 Mon Sep 17 00:00:00 2001
From: Wilmer Arambula <terabytesoftw@gmail.com>
Date: Sun, 29 Jun 2025 06:28:43 -0400
Subject: [PATCH 28/28] fix: Correct typo in development configuration in
 mutation job.

---
 .github/workflows/mutation.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/mutation.yml b/.github/workflows/mutation.yml
index e2dcd58..c95057f 100644
--- a/.github/workflows/mutation.yml
+++ b/.github/workflows/mutation.yml
@@ -21,7 +21,7 @@ jobs:
   mutation:
     uses: php-forge/actions/.github/workflows/infection.yml@main
     with:
-      devolopment: true
+      development: true
       phpstan: true
     secrets:
       STRYKER_DASHBOARD_API_KEY: ${{ secrets.STRYKER_DASHBOARD_API_KEY }}