Added additional tests

tests/Services/LogSystem/LogDiffFormatterTest.php

@@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ *  Copyright (C) 2019 - 2026 Jan Böhmer (https://github.com/jbtronics)
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU Affero General Public License as published
+ *  by the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU Affero General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Affero General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace App\Tests\Services\LogSystem;
+
+use App\Services\LogSystem\LogDiffFormatter;
+use PHPUnit\Framework\TestCase;
+
+final class LogDiffFormatterTest extends TestCase
+{
+    private LogDiffFormatter $service;
+
+    protected function setUp(): void
+    {
+        $this->service = new LogDiffFormatter();
+    }
+
+    public function testPositiveNumericDiff(): void
+    {
+        $result = $this->service->formatDiff(1, 6);
+        $this->assertStringContainsString('text-success', $result);
+        $this->assertStringContainsString('+5', $result);
+    }
+
+    public function testNegativeNumericDiff(): void
+    {
+        $result = $this->service->formatDiff(10, 3);
+        $this->assertStringContainsString('text-danger', $result);
+        $this->assertStringContainsString('-7', $result);
+    }
+
+    public function testZeroNumericDiff(): void
+    {
+        $result = $this->service->formatDiff(5, 5);
+        $this->assertStringContainsString('text-muted', $result);
+        $this->assertStringContainsString('0', $result);
+    }
+
+    public function testStringDiffReturnsNonEmptyHtml(): void
+    {
+        $result = $this->service->formatDiff('hello world', 'hello PHP');
+        $this->assertNotEmpty($result);
+        // DiffHelper returns HTML
+        $this->assertStringContainsString('<', $result);
+    }
+
+    public function testUnsupportedTypesReturnEmptyString(): void
+    {
+        // booleans are neither string nor numeric → empty
+        $result = $this->service->formatDiff(true, false);
+        $this->assertSame('', $result);
+    }
+
+    public function testFloatDiff(): void
+    {
+        $result = $this->service->formatDiff(1.5, 3.0);
+        $this->assertStringContainsString('text-success', $result);
+    }
+}