diff --git a/.gitignore b/.gitignore
index 31e0180..569ac1a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,4 +4,5 @@ coverage/
 node_modules/
 vendor/
 
+.phpunit.cache
 .phpunit.result.cache
diff --git a/README.md b/README.md
index de6e9b8..d9ec707 100644
--- a/README.md
+++ b/README.md
@@ -39,7 +39,7 @@ The current changelog can be found under [source/changelog.txt](source/changelog
 
 - Run ESLint: `npm run eslint`
 - Run JavaScript code coverage with tests: `npm run coverage`
-- Run tests: `npm test` & `./vendor/bin/phpunit tests` (`composer dump-autoload -o` after newly created class)
+- Run tests: `npm test` & `./vendor/bin/phpunit` (`composer dump-autoload` after newly created class)
 - Delete build folder: `npm run clean`
 - Update PHP dependencies: `composer update`
 - Check for direct PHP dependency updates: `composer outdated --direct`
diff --git a/composer.json b/composer.json
index d6a3430..69806a6 100644
--- a/composer.json
+++ b/composer.json
@@ -1,8 +1,8 @@
 {
   "autoload": {
-    "classmap": [
-      "source/includes"
-    ]
+    "psr-4": {
+      "MobilizonConnector\\": "source/includes/"
+    }
   },
   "require-dev": {
     "phpunit/phpunit": "^9.6"
diff --git a/composer.lock b/composer.lock
index 31e8407..7814239 100644
--- a/composer.lock
+++ b/composer.lock
@@ -9,30 +9,30 @@
     "packages-dev": [
         {
             "name": "doctrine/instantiator",
-            "version": "1.5.0",
+            "version": "2.0.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/doctrine/instantiator.git",
-                "reference": "0a0fa9780f5d4e507415a065172d26a98d02047b"
+                "reference": "c6222283fa3f4ac679f8b9ced9a4e23f163e80d0"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/doctrine/instantiator/zipball/0a0fa9780f5d4e507415a065172d26a98d02047b",
-                "reference": "0a0fa9780f5d4e507415a065172d26a98d02047b",
+                "url": "https://api.github.com/repos/doctrine/instantiator/zipball/c6222283fa3f4ac679f8b9ced9a4e23f163e80d0",
+                "reference": "c6222283fa3f4ac679f8b9ced9a4e23f163e80d0",
                 "shasum": ""
             },
             "require": {
-                "php": "^7.1 || ^8.0"
+                "php": "^8.1"
             },
             "require-dev": {
-                "doctrine/coding-standard": "^9 || ^11",
+                "doctrine/coding-standard": "^11",
                 "ext-pdo": "*",
                 "ext-phar": "*",
-                "phpbench/phpbench": "^0.16 || ^1",
-                "phpstan/phpstan": "^1.4",
-                "phpstan/phpstan-phpunit": "^1",
-                "phpunit/phpunit": "^7.5 || ^8.5 || ^9.5",
-                "vimeo/psalm": "^4.30 || ^5.4"
+                "phpbench/phpbench": "^1.2",
+                "phpstan/phpstan": "^1.9.4",
+                "phpstan/phpstan-phpunit": "^1.3",
+                "phpunit/phpunit": "^9.5.27",
+                "vimeo/psalm": "^5.4"
             },
             "type": "library",
             "autoload": {
@@ -59,7 +59,7 @@
             ],
             "support": {
                 "issues": "https://github.com/doctrine/instantiator/issues",
-                "source": "https://github.com/doctrine/instantiator/tree/1.5.0"
+                "source": "https://github.com/doctrine/instantiator/tree/2.0.0"
             },
             "funding": [
                 {
@@ -75,7 +75,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2022-12-30T00:15:36+00:00"
+            "time": "2022-12-30T00:23:10+00:00"
         },
         {
             "name": "myclabs/deep-copy",
@@ -138,16 +138,16 @@
         },
         {
             "name": "nikic/php-parser",
-            "version": "v4.15.4",
+            "version": "v4.15.5",
             "source": {
                 "type": "git",
                 "url": "https://github.com/nikic/PHP-Parser.git",
-                "reference": "6bb5176bc4af8bcb7d926f88718db9b96a2d4290"
+                "reference": "11e2663a5bc9db5d714eedb4277ee300403b4a9e"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/nikic/PHP-Parser/zipball/6bb5176bc4af8bcb7d926f88718db9b96a2d4290",
-                "reference": "6bb5176bc4af8bcb7d926f88718db9b96a2d4290",
+                "url": "https://api.github.com/repos/nikic/PHP-Parser/zipball/11e2663a5bc9db5d714eedb4277ee300403b4a9e",
+                "reference": "11e2663a5bc9db5d714eedb4277ee300403b4a9e",
                 "shasum": ""
             },
             "require": {
@@ -188,9 +188,9 @@
             ],
             "support": {
                 "issues": "https://github.com/nikic/PHP-Parser/issues",
-                "source": "https://github.com/nikic/PHP-Parser/tree/v4.15.4"
+                "source": "https://github.com/nikic/PHP-Parser/tree/v4.15.5"
             },
-            "time": "2023-03-05T19:49:14+00:00"
+            "time": "2023-05-19T20:20:00+00:00"
         },
         {
             "name": "phar-io/manifest",
@@ -623,16 +623,16 @@
         },
         {
             "name": "phpunit/phpunit",
-            "version": "9.6.7",
+            "version": "9.6.8",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit.git",
-                "reference": "c993f0d3b0489ffc42ee2fe0bd645af1538a63b2"
+                "reference": "17d621b3aff84d0c8b62539e269e87d8d5baa76e"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/c993f0d3b0489ffc42ee2fe0bd645af1538a63b2",
-                "reference": "c993f0d3b0489ffc42ee2fe0bd645af1538a63b2",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/17d621b3aff84d0c8b62539e269e87d8d5baa76e",
+                "reference": "17d621b3aff84d0c8b62539e269e87d8d5baa76e",
                 "shasum": ""
             },
             "require": {
@@ -706,7 +706,7 @@
             "support": {
                 "issues": "https://github.com/sebastianbergmann/phpunit/issues",
                 "security": "https://github.com/sebastianbergmann/phpunit/security/policy",
-                "source": "https://github.com/sebastianbergmann/phpunit/tree/9.6.7"
+                "source": "https://github.com/sebastianbergmann/phpunit/tree/9.6.8"
             },
             "funding": [
                 {
@@ -722,7 +722,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2023-04-14T08:58:40+00:00"
+            "time": "2023-05-11T05:14:45+00:00"
         },
         {
             "name": "sebastian/cli-parser",
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..5a15cdb
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.6/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         cacheResultFile=".phpunit.cache/test-results"
+         executionOrder="depends,defects"
+         forceCoversAnnotation="false"
+         beStrictAboutCoversAnnotation="true"
+         beStrictAboutOutputDuringTests="true"
+         beStrictAboutTodoAnnotatedTests="true"
+         convertDeprecationsToExceptions="true"
+         failOnRisky="true"
+         failOnWarning="true"
+         verbose="true">
+    <testsuites>
+        <testsuite name="default">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+
+    <coverage cacheDirectory=".phpunit.cache/code-coverage"
+              processUncoveredFiles="true">
+        <include>
+            <directory suffix=".php">source/includes</directory>
+        </include>
+    </coverage>
+</phpunit>
diff --git a/source/includes/date-time-wrapper.php b/source/includes/DateTimeWrapper.php
similarity index 92%
rename from source/includes/date-time-wrapper.php
rename to source/includes/DateTimeWrapper.php
index 2ffb03d..30fde7a 100644
--- a/source/includes/date-time-wrapper.php
+++ b/source/includes/DateTimeWrapper.php
@@ -1,11 +1,6 @@
 <?php
 namespace MobilizonConnector;
 
-// Exit if this file is called directly.
-if (!defined('ABSPATH')) {
-  exit;
-}
-
 final class DateTimeWrapper {
   private $dateTime;
   private $locale;
diff --git a/source/includes/formatter.php b/source/includes/Formatter.php
similarity index 94%
rename from source/includes/formatter.php
rename to source/includes/Formatter.php
index bff30c9..88816db 100644
--- a/source/includes/formatter.php
+++ b/source/includes/Formatter.php
@@ -1,11 +1,6 @@
 <?php
 namespace MobilizonConnector;
 
-// Exit if this file is called directly.
-if (!defined('ABSPATH')) {
-  exit;
-}
-
 final class Formatter
 {
   public static function format_date(string $locale, string $timeZone, string $start, ?string $end, bool $isShortOffsetNameShown): string {
diff --git a/source/includes/graphql-client.php b/source/includes/GraphQlClient.php
similarity index 100%
rename from source/includes/graphql-client.php
rename to source/includes/GraphQlClient.php
diff --git a/source/includes/settings.php b/source/includes/Settings.php
similarity index 100%
rename from source/includes/settings.php
rename to source/includes/Settings.php
diff --git a/tests/DateTimeWrapperTest.php b/tests/DateTimeWrapperTest.php
index 7739201..09b07e7 100644
--- a/tests/DateTimeWrapperTest.php
+++ b/tests/DateTimeWrapperTest.php
@@ -1,44 +1,47 @@
 <?php
+declare(strict_types=1);
+
+use MobilizonConnector\DateTimeWrapper;
 use PHPUnit\Framework\TestCase;
 
 final class DateTimeWrapperTest extends TestCase {
   public function testCanGetShortDateForUsualDate(): void {
     $d = new DateTimeWrapper('2020-12-24T16:45:00Z');
-    $this->assertEquals('24/12/2020', $d->getShortDate());
+    $this->assertSame('24/12/2020', $d->getShortDate());
   }
 
   public function testCanGetShortDateForUsualDateWithLocaleWithUnderscore(): void {
     $d = new DateTimeWrapper('2020-12-24T16:45:00Z');
-    $this->assertEquals('24/12/2020', $d->getShortDate(), 'en_GB');
+    $this->assertSame('24/12/2020', $d->getShortDate(), 'en_GB');
   }
 
   public function testCanGetShortDateForUsualDateWithTimezoneString(): void {
     $d = new DateTimeWrapper('2020-12-24T16:45:00Z', 'en-GB', 'Europe/Rome');
-    $this->assertEquals('24/12/2020', $d->getShortDate());
+    $this->assertSame('24/12/2020', $d->getShortDate());
   }
 
   public function testCanGetShortDateForUsualDateWithNamedOffset(): void {
     $d = new DateTimeWrapper('2020-12-24T16:45:00Z', 'en-GB', 'UTC');
-    $this->assertEquals('24/12/2020', $d->getShortDate());
+    $this->assertSame('24/12/2020', $d->getShortDate());
   }
 
   public function testCanGetShortDateForUsualDateWithOffset(): void {
     $d = new DateTimeWrapper('2020-12-24T16:45:00Z', 'en-GB', '+02:00');
-    $this->assertEquals('24/12/2020', $d->getShortDate());
+    $this->assertSame('24/12/2020', $d->getShortDate());
   }
 
   public function testCanGetShortDateForUsualDateWithEmptyTimezone(): void {
     $d = new DateTimeWrapper('2020-12-24T16:45:00Z', 'en-GB', '');
-    $this->assertEquals('24/12/2020', $d->getShortDate());
+    $this->assertSame('24/12/2020', $d->getShortDate());
   }
 
   public function testCanGet24TimeForUsualTime(): void {
     $d = new DateTimeWrapper('2020-12-24T16:45:00Z');
-    $this->assertEquals('16:45', $d->get24Time());
+    $this->assertSame('16:45', $d->get24Time());
   }
 
   public function testCanGetShortOffsetNameForUsualTime(): void {
     $d = new DateTimeWrapper('2020-12-24T16:45:00Z');
-    $this->assertEquals(0, $d->getOffset()); // TODO was UTC
+    $this->assertSame('0', $d->getOffset()); // TODO was UTC
   }
 }
diff --git a/tests/FormatterTest.php b/tests/FormatterTest.php
index b4e7006..80d4bd3 100644
--- a/tests/FormatterTest.php
+++ b/tests/FormatterTest.php
@@ -1,45 +1,52 @@
 <?php
+declare(strict_types=1);
+
+use MobilizonConnector\Formatter;
 use PHPUnit\Framework\TestCase;
 
-final class FormatterTest extends TestCase
+final class FormatterTest extends PHPUnit\Framework\TestCase
 {
   public function testCanDateFormatOneDate(): void {
-    $this->assertEquals('15/04/2021 10:30 - 15:30', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', '2021-04-15T15:30:00Z', false));
+    $this->assertSame('15/04/2021 10:30 - 15:30', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', '2021-04-15T15:30:00Z', false));
   }
 
   public function testCanDateFormatOneDateWithOffset(): void {
-    $this->assertEquals('15/04/2021 10:30 - 15:30 (0)', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', '2021-04-15T15:30:00Z', true));
+    $this->assertSame('15/04/2021 10:30 - 15:30 (0)', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', '2021-04-15T15:30:00Z', true));
+  }
+
+  public function testCanDateFormatOneDateWithTimeZoneOffset(): void {
+    $this->assertSame('15/04/2021 11:30 - 16:30', Formatter::format_date('en-GB', '+01:00', '2021-04-15T10:30:00Z', '2021-04-15T15:30:00Z', false));
   }
 
   public function testCanDateFormatTwoDates(): void {
-    $this->assertEquals('15/04/2021 10:30 - 16/04/2021 15:30', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', '2021-04-16T15:30:00Z', false));
+    $this->assertSame('15/04/2021 10:30 - 16/04/2021 15:30', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', '2021-04-16T15:30:00Z', false));
   }
 
   public function testCanDateFormatTwoDatesWithOffset(): void {
-    $this->assertEquals('15/04/2021 10:30 - 16/04/2021 15:30 (0)', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', '2021-04-16T15:30:00Z', true));
+    $this->assertSame('15/04/2021 10:30 - 16/04/2021 15:30 (0)', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', '2021-04-16T15:30:00Z', true));
   }
 
   public function testCanDateFormatWhenSecondDateIsNull(): void {
-    $this->assertEquals('15/04/2021 10:30', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', null, false));
+    $this->assertSame('15/04/2021 10:30', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', null, false));
   }
 
   public function testCanDateFormatWhenSecondDateIsNullWithOffset(): void {
-    $this->assertEquals('15/04/2021 10:30 (0)', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', null, true));
+    $this->assertSame('15/04/2021 10:30 (0)', Formatter::format_date('en-GB', 'UTC', '2021-04-15T10:30:00Z', null, true));
   }
 
   public function testCanLocationFormatBothParameters(): void {
-    $this->assertEquals('a, b', Formatter::format_location('a', 'b'));
+    $this->assertSame('a, b', Formatter::format_location('a', 'b'));
   }
 
   public function testLocationFormatDescriptionOnly(): void {
-    $this->assertEquals('a', Formatter::format_location('a', ''));
+    $this->assertSame('a', Formatter::format_location('a', ''));
   }
 
-  public function testLocationFormatDescriptionWithSpaceOnly() {
-    $this->assertEquals('', Formatter::format_location(' ', ''));
+  public function testLocationFormatDescriptionWithSpaceOnly(): void {
+    $this->assertSame('', Formatter::format_location(' ', ''));
   }
 
   public function testLocationFormatLocalityOnly(): void {
-    $this->assertEquals('a', Formatter::format_location('', 'a'));
+    $this->assertSame('a', Formatter::format_location('', 'a'));
   }
 }