diff --git a/.circleci/config.yml b/.circleci/config.yml
index 0529e53..e9f7a99 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -1,25 +1,17 @@
 version: 2
 
 jobs:
-  "php-7.2":
-    docker:
-      - image: circleci/php:7.2
-    steps:
-      - checkout
-      - run: composer install
-      - run: ./vendor/bin/phpunit
-
-  "php-8.0":
+  "php-8.1":
     docker:
-      - image: circleci/php:8.0
+      - image: cimg/php:8.1
     steps:
       - checkout
       - run: composer install
       - run: ./vendor/bin/phpunit
 
-  "php-8.1":
+  "php-8.2":
     docker:
-      - image: cimg/php:8.1
+      - image: cimg/php:8.2
     steps:
       - checkout
       - run: composer install
@@ -29,6 +21,5 @@ workflows:
     version: 2
     build:
         jobs:
-            - "php-7.2"
-            - "php-8.0"
             - "php-8.1"
+            - "php-8.2"
diff --git a/README.md b/README.md
index 0f74a9e..616e9c3 100644
--- a/README.md
+++ b/README.md
@@ -19,9 +19,12 @@ Create an instance of GamejoltApi and provide a GamejoltConfig
 to begin making API calls to Game Jolt.
 
 ```php
+$gameId = 0; // Your game's ID
+$gamePrivaykey = "Your game's private key";
+
 $api = new GamejoltApi(new GamejoltConfig(
-    'mygameid',
-    'mygameprivatekey'
+    $gameId,
+    $gamePrivaykey
 ));
 ```
 
diff --git a/composer.json b/composer.json
index d41f418..daecc3c 100644
--- a/composer.json
+++ b/composer.json
@@ -4,7 +4,7 @@
     "authors": [
         {
             "name": "Harry Kirkman",
-            "homepage": "https://harrykirkman.co.uk"
+            "homepage": "https://harrk.dev"
         }
     ],
     "description": "A PHP library for the Game Jolt API.",
@@ -23,16 +23,16 @@
         }
     },
     "require": {
-        "php": "^7.2|^8.0",
-        "guzzlehttp/guzzle": "^6.5.7|^7.4.5",
+        "php": "^8.1|8.2",
+        "guzzlehttp/guzzle": "^7.5",
         "ext-json": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.5|^9.3.3",
-        "phpstan/phpstan": "^0.11.0|^0.12.0"
+        "phpunit/phpunit": "^10.0",
+        "phpstan/phpstan": "^1.9.18"
     },
     "scripts": {
         "test": "vendor/bin/phpunit",
-        "analyse": "vendor/bin/phpstan analyse ./src --level=5"
+        "analyse": "vendor/bin/phpstan analyse ./src --level 5"
     }
 }
diff --git a/phpunit.xml b/phpunit.xml
index ff118de..f668a85 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -1,27 +1,17 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit bootstrap = "vendor/autoload.php"
-         backupGlobals               = "false"
-         backupStaticAttributes      = "false"
-         colors                      = "true"
-         convertErrorsToExceptions   = "true"
-         convertNoticesToExceptions  = "true"
-         convertWarningsToExceptions = "true"
-         processIsolation            = "false"
-         stopOnFailure               = "false">
-
-    <testsuites>
-        <testsuite name="Project Test Suite">
-            <directory>tests</directory>
-        </testsuite>
-    </testsuites>
-
-    <filter>
-        <whitelist>
-            <directory suffix=".php">src/</directory>
-        </whitelist>
-    </filter>
-
-    <php>
-        <env name="APP_ENV" value="testing"/>
-    </php>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" bootstrap="vendor/autoload.php" backupGlobals="false" colors="true" processIsolation="false" stopOnFailure="false" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.0/phpunit.xsd" cacheDirectory=".phpunit.cache" backupStaticProperties="false">
+  <coverage>
+    <include>
+      <directory suffix=".php">src/</directory>
+    </include>
+  </coverage>
+  <testsuites>
+    <testsuite name="Project Test Suite">
+      <directory>tests</directory>
+      <exclude>tests/GamejoltApiBaseTest.php</exclude>
+    </testsuite>
+  </testsuites>
+  <php>
+    <env name="APP_ENV" value="testing"/>
+  </php>
 </phpunit>
diff --git a/src/ApiCallService.php b/src/ApiCallService.php
index 31727fc..d87e93f 100644
--- a/src/ApiCallService.php
+++ b/src/ApiCallService.php
@@ -3,6 +3,7 @@
 namespace Harrk\GameJoltApi;
 
 use GuzzleHttp\Client;
+use GuzzleHttp\Exception\GuzzleException;
 use Harrk\GameJoltApi\Exceptions\TimeOutException;
 use Harrk\GameJoltApi\Callers\AbstractCaller;
 use GuzzleHttp\Exception\ConnectException;
@@ -35,11 +36,10 @@ public function __construct(AbstractCaller $caller) {
     }
 
     /**
-     * @return array
      * @throws TimeOutException
-     * @throws \GuzzleHttp\Exception\GuzzleException
+     * @throws GuzzleException
      */
-    public function execute() {
+    public function execute(): array {
         try {
             $request = $this->client->request(
                 $this->method,
diff --git a/src/Callers/AbstractCaller.php b/src/Callers/AbstractCaller.php
index 8cfeba5..f441d14 100644
--- a/src/Callers/AbstractCaller.php
+++ b/src/Callers/AbstractCaller.php
@@ -6,28 +6,18 @@
 use Harrk\GameJoltApi\GamejoltConfig;
 
 class AbstractCaller {
+    protected string $uri;
+    protected array $params;
+    protected GamejoltConfig $gameJoltConfig;
 
-    /**
-     * @var string
-     */
-    protected $uri;
 
-    /**
-     * @var array
-     */
-    protected $params;
-
-    /**
-     * @var GamejoltConfig
-     */
-    protected $gameJoltConfig;
-
-
-    public function __construct(GamejoltConfig $gamejoltConfig) {
+    public function __construct(GamejoltConfig $gamejoltConfig)
+    {
         $this->gameJoltConfig = $gamejoltConfig;
     }
 
-    protected function getSignature(string $url, array $params = []) {
+    protected function getSignature(string $url, array $params = []): string
+    {
         $urlWithPrivateKey = $url . $this->gameJoltConfig->getPrivateKey();
         $toHashString = $urlWithPrivateKey;
 
@@ -46,7 +36,8 @@ protected function getSignature(string $url, array $params = []) {
         return sha1($toHashString);
     }
 
-    public function getFullUrl($withSignature = false) {
+    public function getFullUrl(bool $withSignature = false)
+    {
         $url = $this->gameJoltConfig->getEndpoint() . $this->uri . '/';
 
         $url .= '?' . http_build_query($this->getParams());
@@ -58,23 +49,18 @@ public function getFullUrl($withSignature = false) {
         return $url;
     }
 
-    public function call($uri, $params = []) {
+    public function call(string $uri, array $params = []): array
+    {
         $this->uri = $uri;
-        $this->params = array_merge(
-            [
-                'game_id' => $this->gameJoltConfig->getGameId()
-            ],
-            $params
-        );
-
-        $apiCallService = new ApiCallService($this);
+        $this->params = array_merge([
+            'game_id' => $this->gameJoltConfig->getGameId()
+        ], $params);
 
-        return $apiCallService->execute();
+        return (new ApiCallService($this))->execute();
     }
 
-    public function getParams() {
-        return array_filter((array) $this->params, function ($param) {
-            return ! empty($param);
-        });
+    public function getParams(): array
+    {
+        return array_filter($this->params, static fn ($param) => ! empty($param));
     }
 }
diff --git a/src/Callers/DataStore.php b/src/Callers/DataStore.php
index 457955c..8c4d2c1 100644
--- a/src/Callers/DataStore.php
+++ b/src/Callers/DataStore.php
@@ -5,14 +5,14 @@
 use Harrk\GameJoltApi\Exceptions\InvalidParameterException;
 
 class DataStore extends AbstractCaller {
-    const OPERATION_ADD = 'add';
-    const OPERATION_SUBTRACT = 'subtract';
-    const OPERATION_MULTIPLY = 'multiply';
-    const OPERATION_DIVIDE = 'divide';
-    const OPERATION_APPEND = 'append';
-    const OPERATION_PREPEND = 'prepend';
+    public const OPERATION_ADD = 'add';
+    public const OPERATION_SUBTRACT = 'subtract';
+    public const OPERATION_MULTIPLY = 'multiply';
+    public const OPERATION_DIVIDE = 'divide';
+    public const OPERATION_APPEND = 'append';
+    public const OPERATION_PREPEND = 'prepend';
 
-    CONST OPERATIONS = [
+    public const OPERATIONS = [
         self::OPERATION_ADD,
         self::OPERATION_SUBTRACT,
         self::OPERATION_MULTIPLY,
@@ -23,14 +23,9 @@ class DataStore extends AbstractCaller {
 
     /**
      * @link https://gamejolt.com/game-api/doc/data-store/fetch
-     *
-     * @param string $key
-     * @param null|string $username
-     * @param null|string $user_token
-     *
-     * @return array
      */
-    public function fetch($key, $username = null, $user_token = null) {
+    public function fetch(string $key, ?string $username = null, ?string $user_token = null): array
+    {
         return $this->call('data-store', compact(
             'key', 'username', 'user_token'
         ));
@@ -38,14 +33,9 @@ public function fetch($key, $username = null, $user_token = null) {
 
     /**
      * @link https://gamejolt.com/game-api/doc/data-store/get-keys
-     *
-     * @param null|string $pattern
-     * @param null|string $username
-     * @param null|string $user_token
-     *
-     * @return array
      */
-    public function getKeys($pattern = null, $username = null, $user_token = null) {
+    public function getKeys(?string $pattern = null, ?string $username = null, ?string $user_token = null): array
+    {
         return $this->call('data-store/get-keys', compact(
             'pattern', 'username', 'user_token'
         ));
@@ -53,14 +43,9 @@ public function getKeys($pattern = null, $username = null, $user_token = null) {
 
     /**
      * @link https://gamejolt.com/game-api/doc/data-store/remove
-     *
-     * @param string $key
-     * @param null|string $username
-     * @param null|string $user_token
-     *
-     * @return array
      */
-    public function remove($key, $username = null, $user_token = null) {
+    public function remove(string $key, ?string $username = null, ?string $user_token = null): array
+    {
         return $this->call('data-store/remove', compact(
             'key', 'username', 'user_token'
         ));
diff --git a/src/Callers/Friends.php b/src/Callers/Friends.php
index fbe6908..4f49e3e 100644
--- a/src/Callers/Friends.php
+++ b/src/Callers/Friends.php
@@ -6,13 +6,9 @@ class Friends extends AbstractCaller {
 
     /**
      * @link https://gamejolt.com/game-api/doc/friends/fetch
-     *
-     * @param string $username
-     * @param string $user_token
-     *
-     * @return array
      */
-    public function fetch($username, $user_token) {
+    public function fetch(string $username, string $user_token): array
+    {
         return $this->call('friends', compact(
             'username', 'user_token'
         ));
diff --git a/src/Callers/Scores.php b/src/Callers/Scores.php
index 99e8612..8ca7b6e 100644
--- a/src/Callers/Scores.php
+++ b/src/Callers/Scores.php
@@ -6,18 +6,17 @@ class Scores extends AbstractCaller {
 
     /**
      * @link https://gamejolt.com/game-api/doc/scores/fetch
-     *
-     * @param null|string $username
-     * @param null|string $user_token
-     * @param null|integer $table_id
-     * @param null|integer $limit
-     * @param null|string $guest
-     * @param null|integer $better_than
-     * @param null|integer $worse_than
-     *
-     * @return array
      */
-    public function fetch($username = null, $user_token = null, $table_id = null, $limit = null, $guest = null, $better_than = null, $worse_than = null) {
+    public function fetch(
+        ?string $username = null,
+        ?string $user_token = null,
+        ?int $table_id = null,
+        ?int $limit = null,
+        ?string $guest = null,
+        ?int $better_than = null,
+        ?int $worse_than = null
+    ): array
+    {
         return $this->call('scores', compact(
             'username', 'user_token', 'table_id', 'limit', 'guest', 'better_than', 'worse_than'
         ));
@@ -25,26 +24,24 @@ public function fetch($username = null, $user_token = null, $table_id = null, $l
 
     /**
      * @link https://gamejolt.com/game-api/doc/scores/tables
-     *
-     * @return array
      */
-    public function tables() {
+    public function tables(): array
+    {
         return $this->call('scores/tables');
     }
 
     /**
      * @link https://gamejolt.com/game-api/doc/scores/add
-     *
-     * @param string $username
-     * @param string $user_token
-     * @param string $score
-     * @param integer $sort
-     * @param null|integer $table_id
-     * @param null|string $extra_data
-     *
-     * @return array
      */
-    public function addUserScore($username, $user_token, $score, $sort, $table_id = null, $extra_data = null) {
+    public function addUserScore(
+        string $username,
+        string $user_token,
+        string $score,
+        int $sort,
+        ?int $table_id = null,
+        ?string $extra_data = null
+    ): array
+    {
         return $this->call('scores/add', compact(
             'username', 'user_token', 'score', 'sort', 'table_id', 'extra_data'
         ));
@@ -52,16 +49,15 @@ public function addUserScore($username, $user_token, $score, $sort, $table_id =
 
     /**
      * @link https://gamejolt.com/game-api/doc/scores/add
-     *
-     * @param string $guest
-     * @param string $score
-     * @param integer $sort
-     * @param null|integer $table_id
-     * @param null|string $extra_data
-     *
-     * @return array
      */
-    public function addGuestScore($guest, $score, $sort, $table_id = null, $extra_data = null) {
+    public function addGuestScore(
+        string $guest,
+        string $score,
+        int $sort,
+        ?int $table_id = null,
+        ?string $extra_data = null
+    ): array
+    {
         return $this->call('scores/add', compact(
             'guest', 'score', 'sort', 'table_id', 'extra_data'
         ));
@@ -69,13 +65,9 @@ public function addGuestScore($guest, $score, $sort, $table_id = null, $extra_da
 
     /**
      * @link https://gamejolt.com/game-api/doc/scores/get-rank
-     *
-     * @param integer $sort
-     * @param null|integer $table_id
-     *
-     * @return array
      */
-    public function getRank($sort, $table_id = null) {
+    public function getRank(int $sort, ?int $table_id = null): array
+    {
         return $this->call('scores/get-rank', compact('sort', 'table_id'));
     }
 }
diff --git a/src/Callers/Sessions.php b/src/Callers/Sessions.php
index c80c4d6..494c0f5 100644
--- a/src/Callers/Sessions.php
+++ b/src/Callers/Sessions.php
@@ -5,23 +5,19 @@
 use Harrk\GameJoltApi\Exceptions\InvalidParameterException;
 
 class Sessions extends AbstractCaller {
-    const STATUS_ACTIVE = 'active';
-    const STATUS_IDLE = 'idle';
+    public const STATUS_ACTIVE = 'active';
+    public const STATUS_IDLE = 'idle';
 
-    const STATUSES = [
+    public const STATUSES = [
         self::STATUS_ACTIVE,
         self::STATUS_IDLE,
     ];
 
     /**
      * @link https://gamejolt.com/game-api/doc/sessions/open
-     *
-     * @param string $username
-     * @param string $user_token
-     *
-     * @return array
      */
-    public function open($username, $user_token) {
+    public function open(string $username, string $user_token): array
+    {
         return $this->call('sessions/open', compact(
             'username', 'user_token'
         ));
@@ -30,15 +26,10 @@ public function open($username, $user_token) {
     /**
      * @link https://gamejolt.com/game-api/doc/sessions/ping
      *
-     * @param string $username
-     * @param string $user_token
-     * @param string|null $status
-     *
-     * @return array
-     *
      * @throws InvalidParameterException
      */
-    public function ping($username, $user_token, string $status = null) {
+    public function ping(string $username, string $user_token, ?string $status = null): array
+    {
         if (null !== $status) {
             if (! in_array($status, self::STATUSES)) {
                 throw new InvalidParameterException(
@@ -54,13 +45,9 @@ public function ping($username, $user_token, string $status = null) {
 
     /**
      * @link https://gamejolt.com/game-api/doc/sessions/check
-     *
-     * @param string $username
-     * @param string $user_token
-     *
-     * @return array
      */
-    public function check($username, $user_token) {
+    public function check(string $username, string $user_token): array
+    {
         return $this->call('sessions/check', compact(
             'username', 'user_token'
         ));
@@ -68,13 +55,9 @@ public function check($username, $user_token) {
 
     /**
      * @link https://gamejolt.com/game-api/doc/sessions/close
-     *
-     * @param string $username
-     * @param string $user_token
-     *
-     * @return array
      */
-    public function close($username, $user_token) {
+    public function close(string $username, string $user_token): array
+    {
         return $this->call('sessions/close', compact(
             'username', 'user_token'
         ));
diff --git a/src/Callers/Time.php b/src/Callers/Time.php
index c074730..4712d60 100644
--- a/src/Callers/Time.php
+++ b/src/Callers/Time.php
@@ -6,10 +6,9 @@ class Time extends AbstractCaller {
 
     /**
      * @link https://gamejolt.com/game-api/doc/time/fetch
-     *
-     * @return array
      */
-    public function fetch() {
+    public function fetch(): array
+    {
         return $this->call('time/time');
     }
 
diff --git a/src/Callers/Trophies.php b/src/Callers/Trophies.php
index be5595b..f0a3386 100644
--- a/src/Callers/Trophies.php
+++ b/src/Callers/Trophies.php
@@ -6,15 +6,9 @@ class Trophies extends AbstractCaller {
 
     /**
      * @link https://gamejolt.com/game-api/doc/trophies/fetch
-     *
-     * @param string $username
-     * @param string $user_token
-     * @param bool $achieved
-     * @param integer[] $trophy_ids
-     *
-     * @return array
      */
-    public function fetch($username, $user_token, $achieved = false, array $trophy_ids = []) {
+    public function fetch(string $username, string $user_token, bool $achieved = false, array $trophy_ids = []): array
+    {
         $trophy_id = implode(',', $trophy_ids);
 
         return $this->call('trophies', compact(
@@ -24,14 +18,9 @@ public function fetch($username, $user_token, $achieved = false, array $trophy_i
 
     /**
      * @link https://gamejolt.com/game-api/doc/trophies/add-achieved
-     *
-     * @param string $username
-     * @param string $user_token
-     * @param integer $trophy_id
-     *
-     * @return array
      */
-    public function addAchieved($username, $user_token, $trophy_id) {
+    public function addAchieved(string $username, string $user_token, int $trophy_id): array
+    {
         return $this->call('trophies/add-achieved', compact(
             'username', 'user_token', 'trophy_id'
         ));
@@ -39,14 +28,9 @@ public function addAchieved($username, $user_token, $trophy_id) {
 
     /**
      * @link https://gamejolt.com/game-api/doc/trophies/remove-achieved
-     *
-     * @param string $username
-     * @param string $user_token
-     * @param integer $trophy_id
-     *
-     * @return array
      */
-    public function removeAchieved($username, $user_token, $trophy_id) {
+    public function removeAchieved(string $username, string $user_token, int $trophy_id): array
+    {
         return $this->call('trophies/remove-achieved', compact(
             'username', 'user_token', 'trophy_id'
         ));
diff --git a/src/Callers/Users.php b/src/Callers/Users.php
index 3a489cc..fc2b3c0 100644
--- a/src/Callers/Users.php
+++ b/src/Callers/Users.php
@@ -6,13 +6,9 @@ class Users extends AbstractCaller {
 
     /**
      * @link https://gamejolt.com/game-api/doc/users/fetch
-     *
-     * @param string $username
-     * @param string $user_token
-     *
-     * @return array
      */
-    public function fetch($username, $user_token) {
+    public function fetch(string $username, string $user_token): array
+    {
         return $this->call('users', compact(
             'username', 'user_token'
         ));
@@ -20,13 +16,9 @@ public function fetch($username, $user_token) {
 
     /**
      * @link https://gamejolt.com/game-api/doc/users/auth
-     *
-     * @param string $username
-     * @param string $user_token
-     *
-     * @return array
      */
-    public function auth($username, $user_token) {
+    public function auth(string $username, string $user_token): array
+    {
         return $this->call('users/auth', compact(
             'username', 'user_token'
         ));
diff --git a/src/Exceptions/InvalidParameterException.php b/src/Exceptions/InvalidParameterException.php
index 7228d34..0c06418 100644
--- a/src/Exceptions/InvalidParameterException.php
+++ b/src/Exceptions/InvalidParameterException.php
@@ -2,5 +2,7 @@
 
 namespace Harrk\GameJoltApi\Exceptions;
 
-class InvalidParameterException extends \Exception {
+use Exception;
+
+class InvalidParameterException extends Exception {
 }
diff --git a/src/Exceptions/TimeOutException.php b/src/Exceptions/TimeOutException.php
index 763a38d..3bfa2ba 100644
--- a/src/Exceptions/TimeOutException.php
+++ b/src/Exceptions/TimeOutException.php
@@ -2,5 +2,7 @@
 
 namespace Harrk\GameJoltApi\Exceptions;
 
-class TimeOutException extends \Exception {
+use Exception;
+
+class TimeOutException extends Exception {
 }
diff --git a/src/GamejoltApi.php b/src/GamejoltApi.php
index 65f4b8a..131b7e5 100644
--- a/src/GamejoltApi.php
+++ b/src/GamejoltApi.php
@@ -11,73 +11,69 @@
 use Harrk\GameJoltApi\Callers\Users;
 
 class GamejoltApi {
-
-    /**
-     * @var GamejoltConfig
-     */
-    protected $gameJoltConfig;
+    protected GamejoltConfig $gameJoltConfig;
 
     /**
      * Initialise the API with a provided config
-     * @param GamejoltConfig $gamejoltConfig
      */
-    public function __construct(GamejoltConfig $gamejoltConfig) {
+    public function __construct(GamejoltConfig $gamejoltConfig)
+    {
         $this->gameJoltConfig = $gamejoltConfig;
     }
 
     /**
      * Access the time API
-     * @return Time
      */
-    public function time(): Time {
+    public function time(): Time
+    {
         return new Time($this->gameJoltConfig);
     }
 
     /**
      * Access the trophies API
-     * @return Trophies
      */
-    public function trophies(): Trophies {
+    public function trophies(): Trophies
+    {
         return new Trophies($this->gameJoltConfig);
     }
 
     /**
      * Access the users API
-     * @return Users
      */
-    public function users(): Users {
+    public function users(): Users
+    {
         return new Users($this->gameJoltConfig);
     }
 
     /**
      * Access the sessions API
-     * @return Sessions
      */
-    public function sessions(): Sessions {
+    public function sessions(): Sessions
+    {
         return new Sessions($this->gameJoltConfig);
     }
 
     /**
      * Access the scores API
-     * @return Scores
      */
-    public function scores(): Scores {
+    public function scores(): Scores
+    {
         return new Scores($this->gameJoltConfig);
     }
 
     /**
      * Access the dataStore API
-     * @return DataStore
      */
-    public function dataStore(): DataStore {
+    public function dataStore(): DataStore
+    {
         return new DataStore($this->gameJoltConfig);
     }
 
     /**
      * Access the friends API
-     * @return Friends
      */
-    public function friends(): Friends {
+    public function friends(): Friends
+    {
         return new Friends($this->gameJoltConfig);
     }
 
diff --git a/src/GamejoltConfig.php b/src/GamejoltConfig.php
index 48f3ae6..82e4755 100644
--- a/src/GamejoltConfig.php
+++ b/src/GamejoltConfig.php
@@ -3,28 +3,12 @@
 namespace Harrk\GameJoltApi;
 
 class GamejoltConfig {
+    protected string $endpoint = 'https://api.gamejolt.com/api/game/v1_2/';
+    protected string $privateKey;
+    protected int $gameId;
 
-    /**
-     * @var string Game Jolt API Endpoint
-     */
-    protected $endpoint = 'https://api.gamejolt.com/api/game/v1_2/';
-
-    /**
-     * @var string Game Jolt game private key
-     */
-    protected $privateKey;
-
-    /**
-     * @var int Game Jolt game ID
-     */
-    protected $gameId;
-
-    /**
-     * @param int $gameId
-     * @param string $privateKey
-     * @param null|string $endpoint
-     */
-    public function __construct($gameId, $privateKey, $endpoint = null) {
+    public function __construct(int $gameId, string $privateKey, ?string $endpoint = null)
+    {
         $this->privateKey = $privateKey;
         $this->gameId = $gameId;
 
@@ -35,25 +19,25 @@ public function __construct($gameId, $privateKey, $endpoint = null) {
 
     /**
      * Retrieve the game's private key
-     * @return string
      */
-    public function getPrivateKey() {
+    public function getPrivateKey(): string
+    {
         return $this->privateKey;
     }
 
     /**
      * Retrieve the game's id
-     * @return int
      */
-    public function getGameId() {
+    public function getGameId(): int
+    {
         return $this->gameId;
     }
 
     /**
      * Retrieve Game Jolt's API endpoint
-     * @return string
      */
-    public function getEndpoint() {
+    public function getEndpoint(): string
+    {
         return $this->endpoint;
     }
 }
diff --git a/tests/GamejoltApiBaseTest.php b/tests/GamejoltApiBaseTest.php
new file mode 100644
index 0000000..6cf05e7
--- /dev/null
+++ b/tests/GamejoltApiBaseTest.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Harrk\GameJoltApi\Tests;
+
+use Harrk\GameJoltApi\GamejoltApi;
+use Harrk\GameJoltApi\GamejoltConfig;
+use PHPUnit\Framework\TestCase;
+
+abstract class GamejoltApiBaseTest extends TestCase
+{
+    protected GamejoltApi $api;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $config = new GamejoltConfig(
+            0,
+            'my-game-private-key'
+        );
+
+        $this->api = new GamejoltApi($config);
+    }
+}
diff --git a/tests/GamejoltApiDataStoreTest.php b/tests/GamejoltApiDataStoreTest.php
new file mode 100644
index 0000000..5f1e4ee
--- /dev/null
+++ b/tests/GamejoltApiDataStoreTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Harrk\GameJoltApi\Tests;
+
+use Harrk\GameJoltApi\Callers\DataStore;
+
+class GamejoltApiDataStoreTest extends GamejoltApiBaseTest
+{
+    public function testDataStore(): void
+    {
+        $dataStore = $this->api->dataStore();
+
+        $this->assertEquals(DataStore::class, get_class($dataStore));
+    }
+}
diff --git a/tests/GamejoltApiFriendsTest.php b/tests/GamejoltApiFriendsTest.php
new file mode 100644
index 0000000..6249811
--- /dev/null
+++ b/tests/GamejoltApiFriendsTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Harrk\GameJoltApi\Tests;
+
+use Harrk\GameJoltApi\Callers\Friends;
+
+class GamejoltApiFriendsTest extends GamejoltApiBaseTest
+{
+    public function testFriends(): void
+    {
+        $friends = $this->api->friends();
+
+        $this->assertEquals(Friends::class, get_class($friends));
+    }
+}
diff --git a/tests/GamejoltApiScoresTest.php b/tests/GamejoltApiScoresTest.php
new file mode 100644
index 0000000..b39356f
--- /dev/null
+++ b/tests/GamejoltApiScoresTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Harrk\GameJoltApi\Tests;
+
+use Harrk\GameJoltApi\Callers\Scores;
+
+class GamejoltApiScoresTest extends GamejoltApiBaseTest
+{
+    public function testScores(): void
+    {
+        $scores = $this->api->scores();
+
+        $this->assertEquals(Scores::class, get_class($scores));
+    }
+}
diff --git a/tests/GamejoltApiSessionsTest.php b/tests/GamejoltApiSessionsTest.php
new file mode 100644
index 0000000..a947773
--- /dev/null
+++ b/tests/GamejoltApiSessionsTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Harrk\GameJoltApi\Tests;
+
+use Harrk\GameJoltApi\Callers\Sessions;
+
+class GamejoltApiSessionsTest extends GamejoltApiBaseTest
+{
+    public function testSessions(): void
+    {
+        $sessions = $this->api->sessions();
+
+        $this->assertEquals(Sessions::class, get_class($sessions));
+    }
+}
diff --git a/tests/GamejoltApiTest.php b/tests/GamejoltApiTest.php
deleted file mode 100644
index e9bac39..0000000
--- a/tests/GamejoltApiTest.php
+++ /dev/null
@@ -1,74 +0,0 @@
-<?php
-
-namespace Harrk\GameJoltApi\Tests;
-
-use Harrk\GameJoltApi\Callers\DataStore;
-use Harrk\GameJoltApi\Callers\Friends;
-use Harrk\GameJoltApi\Callers\Scores;
-use Harrk\GameJoltApi\Callers\Sessions;
-use Harrk\GameJoltApi\Callers\Time;
-use Harrk\GameJoltApi\Callers\Trophies;
-use Harrk\GameJoltApi\Callers\Users;
-use Harrk\GameJoltApi\GamejoltApi;
-use Harrk\GameJoltApi\GamejoltConfig;
-use PHPUnit\Framework\TestCase;
-
-class GamejoltApiTest extends TestCase {
-    /**
-     * @var GamejoltApi
-     */
-    private $api;
-
-    protected function setUp(): void {
-        parent::setUp();
-
-        $config = new GamejoltConfig(
-            'my-game-id',
-            'my-game-private-key'
-        );
-
-        $this->api = new GamejoltApi($config);
-    }
-
-    public function testDataStore() {
-        $dataStore = $this->api->dataStore();
-
-        $this->assertEquals(DataStore::class, get_class($dataStore));
-    }
-
-    public function testFriends() {
-        $friends = $this->api->friends();
-
-        $this->assertEquals(Friends::class, get_class($friends));
-    }
-
-    public function testScores() {
-        $scores = $this->api->scores();
-
-        $this->assertEquals(Scores::class, get_class($scores));
-    }
-
-    public function testSessions() {
-        $sessions = $this->api->sessions();
-
-        $this->assertEquals(Sessions::class, get_class($sessions));
-    }
-
-    public function testTime() {
-        $time = $this->api->time();
-
-        $this->assertEquals(Time::class, get_class($time));
-    }
-
-    public function testTrophies() {
-        $trophies = $this->api->trophies();
-
-        $this->assertEquals(Trophies::class, get_class($trophies));
-    }
-
-    public function testUsers() {
-        $users = $this->api->users();
-
-        $this->assertEquals(Users::class, get_class($users));
-    }
-}
diff --git a/tests/GamejoltApiTimeTest.php b/tests/GamejoltApiTimeTest.php
new file mode 100644
index 0000000..72e3a02
--- /dev/null
+++ b/tests/GamejoltApiTimeTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Harrk\GameJoltApi\Tests;
+
+use Harrk\GameJoltApi\Callers\Time;
+
+class GamejoltApiTimeTest extends GamejoltApiBaseTest
+{
+    public function testTime(): void
+    {
+        $time = $this->api->time();
+
+        $this->assertEquals(Time::class, get_class($time));
+    }
+}
diff --git a/tests/GamejoltApiTrophiesTest.php b/tests/GamejoltApiTrophiesTest.php
new file mode 100644
index 0000000..eca873a
--- /dev/null
+++ b/tests/GamejoltApiTrophiesTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Harrk\GameJoltApi\Tests;
+
+use Harrk\GameJoltApi\Callers\Trophies;
+
+class GamejoltApiTrophiesTest extends GamejoltApiBaseTest
+{
+    public function testTrophies(): void
+    {
+        $trophies = $this->api->trophies();
+
+        $this->assertEquals(Trophies::class, get_class($trophies));
+    }
+}
diff --git a/tests/GamejoltApiUsersTest.php b/tests/GamejoltApiUsersTest.php
new file mode 100644
index 0000000..faf33ac
--- /dev/null
+++ b/tests/GamejoltApiUsersTest.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Harrk\GameJoltApi\Tests;
+
+use Harrk\GameJoltApi\Callers\Users;
+
+class GamejoltApiUsersTest extends GamejoltApiBaseTest
+{
+    public function testUsers(): void
+    {
+        $users = $this->api->users();
+
+        $this->assertEquals(Users::class, get_class($users));
+    }
+}
diff --git a/tests/GamejoltConfigTest.php b/tests/GamejoltConfigTest.php
index aa571e8..d35dda7 100644
--- a/tests/GamejoltConfigTest.php
+++ b/tests/GamejoltConfigTest.php
@@ -12,24 +12,28 @@ class GamejoltConfigTest extends TestCase {
      */
     private $config;
 
-    protected function setUp(): void {
+    protected function setUp(): void
+    {
         parent::setUp();
 
         $this->config = new GamejoltConfig(
-            'my-game-id',
+            0,
             'my-game-private-key'
         );
     }
 
-    public function testConfigGameId() {
-        $this->assertEquals('my-game-id', $this->config->getGameId());
+    public function testConfigGameId(): void
+    {
+        $this->assertEquals(0, $this->config->getGameId());
     }
 
-    public function testConfigPrivateKey() {
+    public function testConfigPrivateKey(): void
+    {
         $this->assertEquals('my-game-private-key', $this->config->getPrivateKey());
     }
 
-    public function testConfigEndpoint() {
+    public function testConfigEndpoint(): void
+    {
         $this->assertEquals('https://api.gamejolt.com/api/game/v1_2/', $this->config->getEndpoint());
     }
 }