diff --git a/composer.json b/composer.json
index 3b5c7c4..fcddb5d 100644
--- a/composer.json
+++ b/composer.json
@@ -17,13 +17,13 @@
         "intercom"
     ],
     "require": {
-        "php": "^5.6|^7.0",
-        "league/oauth2-client": "~2.3"
+        "php": "^8.0",
+        "league/oauth2-client": "^2.6"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.0",
-        "mockery/mockery": "~0.9",
-        "squizlabs/php_codesniffer": "~2.0"
+        "phpunit/phpunit": "^9.5",
+        "mockery/mockery": "^1.5",
+        "squizlabs/php_codesniffer": "^3.6"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index d737314..c73c759 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit backupGlobals="false"
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         backupGlobals="false"
          backupStaticAttributes="false"
          bootstrap="vendor/autoload.php"
          colors="true"
@@ -8,19 +9,19 @@
          convertWarningsToExceptions="true"
          processIsolation="false"
          stopOnFailure="false"
-         syntaxCheck="false">
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
+    <coverage>
+        <include>
+            <directory suffix=".php">./</directory>
+        </include>
+        <exclude>
+            <directory suffix=".php">./vendor</directory>
+            <directory suffix=".php">./tests</directory>
+        </exclude>
+    </coverage>
     <testsuites>
         <testsuite name="Package Test Suite">
             <directory suffix=".php">./tests/</directory>
         </testsuite>
     </testsuites>
-    <filter>
-        <whitelist>
-            <directory suffix=".php">./</directory>
-            <exclude>
-                <directory suffix=".php">./vendor</directory>
-                <directory suffix=".php">./tests</directory>
-            </exclude>
-        </whitelist>
-    </filter>
 </phpunit>
diff --git a/src/Provider/Intercom.php b/src/Provider/Intercom.php
index 597cdaf..86bfb0f 100644
--- a/src/Provider/Intercom.php
+++ b/src/Provider/Intercom.php
@@ -2,25 +2,26 @@
 
 namespace Intercom\OAuth2\Client\Provider;
 
+use JetBrains\PhpStorm\ArrayShape;
 use League\OAuth2\Client\Provider\AbstractProvider;
 use League\OAuth2\Client\Provider\Exception\IdentityProviderException;
+use League\OAuth2\Client\Provider\ResourceOwnerInterface;
 use League\OAuth2\Client\Token\AccessToken;
 use Psr\Http\Message\ResponseInterface;
 
 class Intercom extends AbstractProvider
 {
-
     /**
-     * @var boolean By default Intercom strategy rejects users with unverified email addresses.
+     * @var boolean By default, Intercom strategy rejects users with unverified email addresses.
      */
-    protected $verifyEmail = true;
+    protected bool $verifyEmail = true;
 
     /**
      * Get authorization url to begin OAuth flow
      *
      * @return string
      */
-    public function getBaseAuthorizationUrl()
+    public function getBaseAuthorizationUrl(): string
     {
         return 'https://app.intercom.com/oauth';
     }
@@ -28,9 +29,10 @@ public function getBaseAuthorizationUrl()
     /**
      * Get access token url to retrieve token
      *
+     * @param array $params
      * @return string
      */
-    public function getBaseAccessTokenUrl(array $params)
+    public function getBaseAccessTokenUrl(array $params): string
     {
         return 'https://api.intercom.io/auth/eagle/token';
     }
@@ -42,7 +44,7 @@ public function getBaseAccessTokenUrl(array $params)
      *
      * @return string
      */
-    public function getResourceOwnerDetailsUrl(AccessToken $token)
+    public function getResourceOwnerDetailsUrl(AccessToken $token): string
     {
         return 'https://api.intercom.io/me';
     }
@@ -55,18 +57,19 @@ public function getResourceOwnerDetailsUrl(AccessToken $token)
      *
      * @return array
      */
-    protected function getDefaultScopes()
+    protected function getDefaultScopes(): array
     {
         return [];
     }
 
     /**
      * Check a provider response for errors.
+     * @throws IdentityProviderException
      */
-    protected function checkResponse(ResponseInterface $response, $data)
+    protected function checkResponse(ResponseInterface $response, $data): void
     {
         $statusCode = $response->getStatusCode();
-        if (empty($data['errors']) && $statusCode == 200) {
+        if (empty($data['errors']) && $statusCode === 200) {
             return;
         }
 
@@ -84,7 +87,8 @@ protected function checkResponse(ResponseInterface $response, $data)
      *
      * @return array
      */
-    protected function getDefaultHeaders()
+    #[ArrayShape(['Accept' => "string", 'User-Agent' => "string"])]
+    protected function getDefaultHeaders(): array
     {
         return [ 'Accept' => 'application/json', 'User-Agent' => 'league/oauth2-intercom/2.0.0' ];
     }
@@ -104,10 +108,11 @@ protected function getAuthorizationHeaders($token = null)
     /**
      * Requests resource owner details.
      *
-     * @param  AccessToken $token
+     * @param AccessToken $token
      * @return mixed
+     * @throws IdentityProviderException
      */
-    protected function fetchResourceOwnerDetails(AccessToken $token)
+    protected function fetchResourceOwnerDetails(AccessToken $token): mixed
     {
         $url = $this->getResourceOwnerDetailsUrl($token);
 
@@ -119,14 +124,16 @@ protected function fetchResourceOwnerDetails(AccessToken $token)
     /**
      * Generate a user object from a successful user details request.
      *
-     * @param object $response
+     * @param array $response
      * @param AccessToken $token
-     * @return League\OAuth2\Client\Provider\ResourceOwnerInterface
+     * @return IntercomResourceOwner|ResourceOwnerInterface
      */
-    protected function createResourceOwner(array $response, AccessToken $token)
-    {
+    protected function createResourceOwner(
+        array $response,
+        AccessToken $token
+    ): IntercomResourceOwner|ResourceOwnerInterface {
         $validatedResponse = $response;
-        if ($this->verifyEmail == true && $response['email_verified'] != true) {
+        if ($this->verifyEmail && !$response['email_verified']) {
             $validatedResponse = [];
         }
         return new IntercomResourceOwner($validatedResponse);
diff --git a/tests/src/Provider/IntercomTest.php b/tests/src/Provider/IntercomTest.php
index 8c4a11b..38d036f 100644
--- a/tests/src/Provider/IntercomTest.php
+++ b/tests/src/Provider/IntercomTest.php
@@ -2,28 +2,33 @@
 
 namespace Intercom\OAuth2\Client\Test\Provider;
 
+use Intercom\OAuth2\Client\Provider\Intercom;
+use League\OAuth2\Client\Provider\Exception\IdentityProviderException;
 use Mockery as m;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\ResponseInterface;
+use GuzzleHttp\ClientInterface;
 
-class IntercomTest extends \PHPUnit_Framework_TestCase
+class IntercomTest extends TestCase
 {
-    protected $provider;
+    protected Intercom $provider;
 
-    protected function setUp()
+    protected function setUp(): void
     {
-        $this->provider = new \Intercom\OAuth2\Client\Provider\Intercom([
+        $this->provider = new Intercom([
             'clientId' => 'mock_client_id',
             'clientSecret' => 'mock_secret',
             'redirectUri' => 'none',
         ]);
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         m::close();
         parent::tearDown();
     }
 
-    public function testAuthorizationUrl()
+    public function testAuthorizationUrl(): void
     {
         $url = $this->provider->getAuthorizationUrl(['approval_prompt' => []]);
         $uri = parse_url($url);
@@ -38,32 +43,37 @@ public function testAuthorizationUrl()
         $this->assertNotNull($this->provider->getState());
     }
 
-    public function testGetAuthorizationUrl()
+    public function testGetAuthorizationUrl(): void
     {
         $url = $this->provider->getAuthorizationUrl();
-        $this->assertContains('https://app.intercom.com/oauth', $url);
+        $this->assertStringContainsString('https://app.intercom.com/oauth', $url);
     }
 
-    public function testGetBaseAccessTokenUrl()
+    public function testGetBaseAccessTokenUrl(): void
     {
         $url = $this->provider->getBaseAccessTokenUrl([]);
-        $this->assertContains('https://api.intercom.io/auth/eagle/token', $url);
+        $this->assertStringContainsString('https://api.intercom.io/auth/eagle/token', $url);
     }
 
-    public function getResourceOwnerDetailsUrl()
+    public function getResourceOwnerDetailsUrl(): void
     {
-        $url = $this->provider->getBaseAccessTokenUrl('mock_token');
-        $this->assertContains('https://api.intercom.io/me', $url);
+        $url = $this->provider->getBaseAccessTokenUrl((array)'mock_token');
+        $this->assertStringContainsString('https://api.intercom.io/me', $url);
     }
 
-    public function testGetAccessToken()
+    /**
+     * @throws IdentityProviderException
+     */
+    public function testGetAccessToken(): void
     {
-        $response = m::mock('Psr\Http\Message\ResponseInterface');
-        $response->shouldReceive('getBody')->andReturn('{"access_token": "mock_access_token", "token_type": "bearer", "uid": "12345"}');
+        $response = m::mock(ResponseInterface::class);
+        $response->shouldReceive('getBody')->andReturn(
+            '{"access_token": "mock_access_token", "token_type": "bearer", "uid": "12345"}'
+        );
         $response->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $response->shouldReceive('getStatusCode')->andReturn(200);
 
-        $client = m::mock('GuzzleHttp\ClientInterface');
+        $client = m::mock(ClientInterface::class);
         $client->shouldReceive('send')->times(1)->andReturn($response);
         $this->provider->setHttpClient($client);
 
@@ -79,11 +89,29 @@ public function testUserData()
     {
         $postResponse = m::mock('Psr\Http\Message\ResponseInterface');
 
-        $postResponse->shouldReceive('getBody')->andReturn('{"token": "mock_access_token", "access_token": "mock_access_token", "token_type": "Bearer"}');
+        $postResponse->shouldReceive('getBody')->andReturn(
+            '{"token": "mock_access_token", "access_token": "mock_access_token", "token_type": "Bearer"}'
+        );
         $postResponse->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $postResponse->shouldReceive('getStatusCode')->andReturn(200);
 
-        $userJson = '{"type":"admin","id":"368312","email":"fizbit@intercom.io","name":"Fizbit Grappleboot","email_verified":true,"app":{"type":"app","id_code":"2qmk5gy1","created_at":1358214715,"secure":true},"avatar":{"type":"avatar", "image_url":"https://static.intercomassets.com/avatars/228311/square_128/1462489937.jpg"}}';
+        $userJson = '{
+            "type":"admin",
+            "id":"368312",
+            "email":"fizbit@intercom.io",
+            "name":"Fizbit Grappleboot",
+            "email_verified":true,
+            "app":{
+                "type":"app",
+                "id_code":"2qmk5gy1",
+                "created_at":1358214715,
+                "secure":true
+            },
+            "avatar":{
+                "type":"avatar",
+                "image_url":"https://static.intercomassets.com/avatars/228311/square_128/1462489937.jpg"
+            }
+        }';
         $userArray = json_decode($userJson, true);
 
         $userResponse = m::mock('Psr\Http\Message\ResponseInterface');
@@ -91,7 +119,7 @@ public function testUserData()
         $userResponse->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $userResponse->shouldReceive('getStatusCode')->andReturn(200);
 
-        $client = m::mock('GuzzleHttp\ClientInterface');
+        $client = m::mock(ClientInterface::class);
         $client->shouldReceive('send')
             ->times(2)
             ->andReturn($postResponse, $userResponse);
@@ -107,15 +135,33 @@ public function testUserData()
         $this->assertEquals($userArray['avatar']['image_url'], $user->getAvatarUrl());
     }
 
-    public function testUserUnverifiedEmail()
+    public function testUserUnverifiedEmail(): void
     {
         $postResponse = m::mock('Psr\Http\Message\ResponseInterface');
 
-        $postResponse->shouldReceive('getBody')->andReturn('{"token": "mock_access_token", "access_token": "mock_access_token", "token_type": "Bearer"}');
+        $postResponse->shouldReceive('getBody')->andReturn(
+            '{"token": "mock_access_token", "access_token": "mock_access_token", "token_type": "Bearer"}'
+        );
         $postResponse->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $postResponse->shouldReceive('getStatusCode')->andReturn(200);
 
-        $userJson = '{"type":"admin","id":"368312","email":"fizbit@intercom.io","name":"Fizbit Grappleboot","email_verified":false,"app":{"type":"app","id_code":"2qmk5gy1","created_at":1358214715,"secure":true},"avatar":{"type":"avatar", "image_url":"https://static.intercomassets.com/avatars/228311/square_128/1462489937.jpg"}}';
+        $userJson = '{
+            "type":"admin",
+            "id":"368312",
+            "email":"fizbit@intercom.io",
+            "name":"Fizbit Grappleboot",
+            "email_verified":false,
+            "app":{
+                "type":"app",
+                "id_code":"2qmk5gy1",
+                "created_at":1358214715,
+                "secure":true
+            },
+            "avatar":{
+                "type":"avatar",
+                "image_url":"https://static.intercomassets.com/avatars/228311/square_128/1462489937.jpg"
+            }
+        }';
         $userArray = json_decode($userJson, true);
 
         $userResponse = m::mock('Psr\Http\Message\ResponseInterface');
@@ -123,7 +169,7 @@ public function testUserUnverifiedEmail()
         $userResponse->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $userResponse->shouldReceive('getStatusCode')->andReturn(200);
 
-        $client = m::mock('GuzzleHttp\ClientInterface');
+        $client = m::mock(ClientInterface::class);
         $client->shouldReceive('send')
             ->times(2)
             ->andReturn($postResponse, $userResponse);
@@ -132,29 +178,44 @@ public function testUserUnverifiedEmail()
         $token = $this->provider->getAccessToken('authorization_code', ['code' => 'mock_authorization_code']);
         $user = $this->provider->getResourceOwner($token);
 
-        $this->assertEquals(array(), $user->toArray());
+        $this->assertEquals([], $user->toArray());
         $this->assertEquals(null, $user->getId());
         $this->assertEquals(null, $user->getEmail());
         $this->assertEquals(null, $user->getName());
         $this->assertEquals(null, $user->getAvatarUrl());
     }
 
-    public function testSkipUserUnverifiedEmailCheck()
+    public function testSkipUserUnverifiedEmailCheck(): void
     {
-        $provider = new \Intercom\OAuth2\Client\Provider\Intercom([
+        $provider = new Intercom([
             'clientId' => 'mock_client_id',
             'clientSecret' => 'mock_secret',
             'redirectUri' => 'none',
-            'verifyEmail' => false
+            'verifyEmail' => false,
         ]);
 
         $postResponse = m::mock('Psr\Http\Message\ResponseInterface');
 
-        $postResponse->shouldReceive('getBody')->andReturn('{"token": "mock_access_token", "access_token": "mock_access_token", "token_type": "Bearer"}');
+        $postResponse->shouldReceive('getBody')->andReturn('{
+            "token": "mock_access_token",
+            "access_token": "mock_access_token",
+            "token_type": "Bearer"
+        }');
         $postResponse->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $postResponse->shouldReceive('getStatusCode')->andReturn(200);
 
-        $userJson = '{"type":"admin","id":"368312","email":"fizbit@intercom.io","name":"Fizbit Grappleboot","email_verified":false,"app":{"type":"app","id_code":"2qmk5gy1","created_at":1358214715,"secure":true},"avatar":{"type":"avatar", "image_url":"https://static.intercomassets.com/avatars/228311/square_128/1462489937.jpg"}}';
+        $userJson = '{
+            "type":"admin",
+            "id":"368312",
+            "email":"fizbit@intercom.io",
+            "name":"Fizbit Grappleboot",
+            "email_verified":false,
+            "app":{"type":"app","id_code":"2qmk5gy1","created_at":1358214715,"secure":true},
+            "avatar":{
+                "type":"avatar",
+                "image_url":"https://static.intercomassets.com/avatars/228311/square_128/1462489937.jpg"
+            }
+        }';
         $userArray = json_decode($userJson, true);
 
         $userResponse = m::mock('Psr\Http\Message\ResponseInterface');
@@ -162,7 +223,7 @@ public function testSkipUserUnverifiedEmailCheck()
         $userResponse->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $userResponse->shouldReceive('getStatusCode')->andReturn(200);
 
-        $client = m::mock('GuzzleHttp\ClientInterface');
+        $client = m::mock(ClientInterface::class);
         $client->shouldReceive('send')
             ->times(2)
             ->andReturn($postResponse, $userResponse);
@@ -179,19 +240,24 @@ public function testSkipUserUnverifiedEmailCheck()
     }
 
     /**
-     * @expectedException League\OAuth2\Client\Provider\Exception\IdentityProviderException
-     **/
-    public function testExceptionThrownWhenErrorResponse()
+     * @throws IdentityProviderException
+     */
+    public function testExceptionThrownWhenErrorResponse(): void
     {
-        $postResponse = m::mock('Psr\Http\Message\ResponseInterface');
+        $this->expectException(IdentityProviderException::class);
+        $postResponse = m::mock(ResponseInterface::class);
 
-        $errorBody = '{"type":"error.list","request_id":"anvt4on87prigma30i8g","errors":[{"code":"server_error","message":"Server Error"}]}';
+        $errorBody = '{
+            "type":"error.list",
+            "request_id":"anvt4on87prigma30i8g",
+            "errors":[{"code":"server_error","message":"Server Error"}]
+        }';
 
         $postResponse->shouldReceive('getBody')->andReturn($errorBody);
         $postResponse->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $postResponse->shouldReceive('getStatusCode')->andReturn(401);
 
-        $client = m::mock('GuzzleHttp\ClientInterface');
+        $client = m::mock(ClientInterface::class);
         $client->shouldReceive('send')
             ->times(1)
             ->andReturn($postResponse);
@@ -200,20 +266,25 @@ public function testExceptionThrownWhenErrorResponse()
     }
 
     /**
-     * @expectedException League\OAuth2\Client\Provider\Exception\IdentityProviderException
-     **/
-    public function testExceptionThrownWhenStatusNotSuccess()
+     * @throws IdentityProviderException
+     */
+    public function testExceptionThrownWhenStatusNotSuccess(): void
     {
-        $postResponse = m::mock('Psr\Http\Message\ResponseInterface');
+        $this->expectException(IdentityProviderException::class);
+        $postResponse = m::mock(ResponseInterface::class);
 
-        $errorBody = '{"type":"error.list","request_id":"anvt4on87prigma30i8g","errors":[{"code":"server_error","message":"Server Error"}]}';
+        $errorBody = '{
+            "type":"error.list",
+            "request_id":"anvt4on87prigma30i8g",
+            "errors":[{"code":"server_error","message":"Server Error"}]
+        }';
 
         $postResponse->shouldReceive('getBody')->andReturn($errorBody);
         $postResponse->shouldReceive('getHeader')->andReturn(['content-type' => 'json']);
         $postResponse->shouldReceive('getReasonPhrase')->andReturn('Internal Server Error');
         $postResponse->shouldReceive('getStatusCode')->andReturn(500);
 
-        $client = m::mock('GuzzleHttp\ClientInterface');
+        $client = m::mock(ClientInterface::class);
         $client->shouldReceive('send')
             ->times(1)
             ->andReturn($postResponse);