chore: implemement basic tests

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

tests/php/bootstrap.php

@@ -0,0 +1,7 @@
+<?php
+
+require dirname(__DIR__, 2).'/lib/vendor/autoload.php';
+
+if (isset($_SERVER['APP_DEBUG']) && $_SERVER['APP_DEBUG']) {
+    umask(0000);
+}

tests/php/phpunit.unit.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!-- https://phpunit.readthedocs.io/en/latest/configuration.html -->
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="../../vendor/phpunit/phpunit/phpunit.xsd"
+         colors="true"
+         failOnDeprecation="true"
+         failOnNotice="true"
+         failOnWarning="true"
+         bootstrap="bootstrap.php"
+         cacheDirectory="../../.phpunit.cache"
+>
+    <php>
+        <ini name="display_errors" value="1" />
+        <ini name="error_reporting" value="-1" />
+        <server name="APP_ENV" value="test" force="true" />
+        <server name="SHELL_VERBOSITY" value="-1" />
+    </php>
+
+    <testsuites>
+        <testsuite name="Unit Tests">
+            <directory>unit</directory>
+        </testsuite>
+    </testsuites>
+
+    <source ignoreSuppressionOfDeprecations="true"
+            ignoreIndirectDeprecations="true"
+            restrictNotices="true"
+            restrictWarnings="true"
+    >
+        <include>
+            <directory>../../core/lib</directory>
+            <directory>../../shared/lib</directory>
+        </include>
+    </source>
+
+    <extensions>
+    </extensions>
+</phpunit>

tests/php/unit/BaseTest.php

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+<?php
+
+namespace KTXT\MailManager\Tests\Unit;
+
+use PHPUnit\Framework\TestCase;
+
+class BaseTest extends TestCase
+{
+    public function testBasicAssertion(): void
+    {
+        $this->assertTrue(true);
+    }
+
+    public function testArrayOperations(): void
+    {
+        $array = ['foo' => 'bar'];
+        
+        $this->assertArrayHasKey('foo', $array);
+        $this->assertEquals('bar', $array['foo']);
+    }
+
+    public function testStringOperations(): void
+    {
+        $string = 'Hello, World!';
+        
+        $this->assertStringContainsString('World', $string);
+        $this->assertEquals(13, strlen($string));
+    }
+}