diff --git a/.travis.yml b/.travis.yml
index e4e9f17..9e8f60d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,8 @@ language: php
 sudo: false
 
 php:
-  - 7.2
+  - 7.3
+  - 8.2
 
 before_script:
   - travis_retry composer self-update
diff --git a/README.md b/README.md
index d24a8d9..3b3fa3e 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@
 [![Total Downloads](https://poser.pugx.org/omnipay/braintree/d/total.png)](https://packagist.org/packages/omnipay/braintree)
 
 [Omnipay](https://github.com/thephpleague/omnipay) is a framework agnostic, multi-gateway payment
-processing library for PHP 7.2+. This package implements Braintree support for Omnipay.
+processing library for PHP 7.3+. This package implements Braintree support for Omnipay.
 
 ## Installation
 
diff --git a/composer.json b/composer.json
index 353f9f0..a7de20f 100644
--- a/composer.json
+++ b/composer.json
@@ -32,10 +32,10 @@
     },
     "require": {
         "omnipay/common": "^3",
-        "braintree/braintree_php": "^5.0"
+        "braintree/braintree_php": "^6.0"
     },
     "require-dev": {
-        "omnipay/tests": "^3"
+        "omnipay/tests": "^4"
     },
     "extra": {
         "branch-alias": {
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 535809e..4f8afb5 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,22 +1,23 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit backupGlobals="false"
-         backupStaticAttributes="false"
-         bootstrap="vendor/autoload.php"
-         colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
-         processIsolation="false"
-         stopOnFailure="false"
-         syntaxCheck="false">
-    <testsuites>
-        <testsuite name="Omnipay Test Suite">
-            <directory>./tests/</directory>
-        </testsuite>
-    </testsuites>
-    <filter>
-        <whitelist>
-            <directory>./src</directory>
-        </whitelist>
-    </filter>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
+    convertWarningsToExceptions="true"
+    convertNoticesToExceptions="true"
+    convertErrorsToExceptions="true"
+    bootstrap="vendor/autoload.php"
+    backupStaticAttributes="false"
+    processIsolation="false"
+    stopOnFailure="false"
+    backupGlobals="false"
+    colors="true">
+  <coverage>
+    <include>
+      <directory>./src</directory>
+    </include>
+  </coverage>
+  <testsuites>
+    <testsuite name="Omnipay Test Suite">
+      <directory>./tests/</directory>
+    </testsuite>
+  </testsuites>
 </phpunit>
diff --git a/src/MerchantIndividual.php b/src/MerchantIndividual.php
index 76ecd24..cc469f3 100644
--- a/src/MerchantIndividual.php
+++ b/src/MerchantIndividual.php
@@ -184,7 +184,7 @@ public function setName($value)
     {
         $names = explode(' ', $value, 2);
         $this->setFirstName($names[0]);
-        $this->setLastName(isset($names[1]) ? $names[1] : null);
+        $this->setLastName($names[1] ?? null);
 
         return $this;
     }
diff --git a/src/Message/AbstractRequest.php b/src/Message/AbstractRequest.php
index 7e946a1..0be01e8 100644
--- a/src/Message/AbstractRequest.php
+++ b/src/Message/AbstractRequest.php
@@ -159,16 +159,6 @@ public function setDeviceData($value)
         return $this->setParameter('deviceData', $value);
     }
 
-    public function getDeviceSessionId()
-    {
-        return $this->getParameter('deviceSessionId');
-    }
-
-    public function setDeviceSessionId($value)
-    {
-        return $this->setParameter('deviceSessionId', $value);
-    }
-
     public function getMerchantAccountId()
     {
         return $this->getParameter('merchantAccountId');
diff --git a/src/Message/AuthorizeRequest.php b/src/Message/AuthorizeRequest.php
index fa8e590..1fba1db 100644
--- a/src/Message/AuthorizeRequest.php
+++ b/src/Message/AuthorizeRequest.php
@@ -23,7 +23,6 @@ public function getData()
             'customerId' => $this->getCustomerId(),
             'descriptor' => $this->getDescriptor(),
             'deviceData' => $this->getDeviceData(),
-            'deviceSessionId' => $this->getDeviceSessionId(),
             'merchantAccountId' => $this->getMerchantAccountId(),
             'orderId' => $this->getTransactionId(),
             'purchaseOrderNumber' => $this->getPurchaseOrderNumber(),
diff --git a/tests/GatewayTest.php b/tests/GatewayTest.php
index 6c616c2..edab2c7 100644
--- a/tests/GatewayTest.php
+++ b/tests/GatewayTest.php
@@ -15,7 +15,12 @@ class GatewayTest extends GatewayTestCase
      */
     protected $gateway;
 
-    public function setUp()
+    /**
+     * @var array
+     */
+    protected $options;
+
+    public function setUp(): void
     {
         parent::setUp();
 
@@ -150,30 +155,21 @@ public function testCancelSubscription()
     public function testParseNotification()
     {
         if(Version::MAJOR >= 3) {
-            $xml = '<notification></notification>';
-            $payload = base64_encode($xml);
-            $signature = Digest::hexDigestSha1(Configuration::privateKey(), $payload);
-            $gatewayMock = $this->buildGatewayMock($payload);
-            $gateway = new Gateway($this->getHttpClient(), $this->getHttpRequest(), $gatewayMock);
-            $params = array(
-                'bt_signature' => $payload.'|'.$signature,
-                'bt_payload' => $payload
-            );
-            $request = $gateway->parseNotification($params);
-            $this->assertInstanceOf('\Braintree\WebhookNotification', $request);
+            $xml = '<notification><subject></subject><kind></kind></notification>';
         } else {
             $xml = '<notification><subject></subject></notification>';
-            $payload = base64_encode($xml);
-            $signature = Digest::hexDigestSha1(Configuration::privateKey(), $payload);
-            $gatewayMock = $this->buildGatewayMock($payload);
-            $gateway = new Gateway($this->getHttpClient(), $this->getHttpRequest(), $gatewayMock);
-            $params = array(
-                'bt_signature' => $payload.'|'.$signature,
-                'bt_payload' => $payload
-            );
-            $request = $gateway->parseNotification($params);
-            $this->assertInstanceOf('\Braintree\WebhookNotification', $request);
         }
+
+        $payload = base64_encode($xml);
+        $signature = Digest::hexDigestSha1(Configuration::privateKey(), $payload);
+        $gatewayMock = $this->buildGatewayMock($payload);
+        $gateway = new Gateway($this->getHttpClient(), $this->getHttpRequest(), $gatewayMock);
+        $params = array(
+            'bt_signature' => $payload.'|'.$signature,
+            'bt_payload' => $payload
+        );
+        $request = $gateway->parseNotification($params);
+        $this->assertInstanceOf('\Braintree\WebhookNotification', $request);
     }
 
     /**
diff --git a/tests/MerchantBusinessTest.php b/tests/MerchantBusinessTest.php
index a788c1a..a7908a7 100644
--- a/tests/MerchantBusinessTest.php
+++ b/tests/MerchantBusinessTest.php
@@ -8,7 +8,12 @@
 
 class MerchantBusinessTest extends TestCase
 {
-    public function setUp()
+    /**
+     * @var MerchantBusiness
+     */
+    protected $business;
+
+    public function setUp(): void
     {
         $this->business = new MerchantBusiness();
     }
diff --git a/tests/MerchantFundingTest.php b/tests/MerchantFundingTest.php
index b31b6ce..78157b2 100644
--- a/tests/MerchantFundingTest.php
+++ b/tests/MerchantFundingTest.php
@@ -7,7 +7,12 @@
 
 class MerchantFundingTest extends TestCase
 {
-    public function setUp()
+    /**
+     * @var MerchantFunding
+     */
+    protected $funding;
+
+    public function setUp(): void
     {
         $this->funding = new MerchantFunding();
     }
diff --git a/tests/MerchantIndividualTest.php b/tests/MerchantIndividualTest.php
index abf9349..e268699 100644
--- a/tests/MerchantIndividualTest.php
+++ b/tests/MerchantIndividualTest.php
@@ -8,7 +8,12 @@
 
 class MerchantIndividualTest extends TestCase
 {
-    public function setUp()
+    /**
+     * @var MerchantIndividual
+     */
+    protected $individual;
+
+    public function setUp(): void
     {
         $this->individual = new MerchantIndividual();
     }
diff --git a/tests/Message/AbstractMerchantAccountRequestTest.php b/tests/Message/AbstractMerchantAccountRequestTest.php
index 05e64b8..4a9c670 100644
--- a/tests/Message/AbstractMerchantAccountRequestTest.php
+++ b/tests/Message/AbstractMerchantAccountRequestTest.php
@@ -13,7 +13,7 @@ class AbstractMerchantAccountRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->request = Mockery::mock('\Omnipay\Braintree\Message\AbstractMerchantAccountRequest')->makePartial();
         $this->request->initialize();
diff --git a/tests/Message/AbstractRequestTest.php b/tests/Message/AbstractRequestTest.php
index ec64ae4..8b5b6f8 100644
--- a/tests/Message/AbstractRequestTest.php
+++ b/tests/Message/AbstractRequestTest.php
@@ -12,7 +12,7 @@ class AbstractRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->request = Mockery::mock('\Omnipay\Braintree\Message\AbstractRequest')->makePartial();
         $this->request->initialize();
@@ -42,7 +42,6 @@ public function provideKeepsData(){
             array('customerId', 'abc123'),
             array('descriptor', array('a' => 'b')),
             array('deviceData', 'abc123'),
-            array('deviceSessionId', 'abc123'),
             array('merchantAccountId', 'abc123'),
             array('recurring', true),
             array('addBillingAddressToPaymentMethod', true),
diff --git a/tests/Message/AuthorizeRequestTest.php b/tests/Message/AuthorizeRequestTest.php
index 54e46e9..0761aa6 100644
--- a/tests/Message/AuthorizeRequestTest.php
+++ b/tests/Message/AuthorizeRequestTest.php
@@ -4,6 +4,7 @@
 
 use Braintree\Configuration;
 use Omnipay\Tests\TestCase;
+use Omnipay\Common\Exception\InvalidRequestException;
 
 class AuthorizeRequestTest extends TestCase
 {
@@ -12,7 +13,7 @@ class AuthorizeRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
@@ -176,23 +177,24 @@ public function testGetServiceFeeAmountNoDecimalsRounding()
         $this->assertSame('137', $this->request->getServiceFeeAmount());
     }
 
-    /**
-     * @expectedException \Omnipay\Common\Exception\InvalidRequestException
-     */
     public function testServiceFeeAmountWithIntThrowsException()
     {
         // ambiguous value, avoid errors upgrading from v0.9
         $this->assertSame($this->request, $this->request->setServiceFeeAmount(10));
+
+        $this->expectException(InvalidRequestException::class);
+
         $this->request->getServiceFeeAmount();
+
     }
 
-    /**
-     * @expectedException \Omnipay\Common\Exception\InvalidRequestException
-     */
     public function testServiceFeeAmountWithIntStringThrowsException()
     {
         // ambiguous value, avoid errors upgrading from v0.9
         $this->assertSame($this->request, $this->request->setServiceFeeAmount('10'));
+
+        $this->expectException(InvalidRequestException::class);
+
         $this->request->getServiceFeeAmount();
     }
 }
diff --git a/tests/Message/CaptureRequestTest.php b/tests/Message/CaptureRequestTest.php
index fb08f86..30de79d 100644
--- a/tests/Message/CaptureRequestTest.php
+++ b/tests/Message/CaptureRequestTest.php
@@ -12,7 +12,7 @@ class CaptureRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/ClientTokenRequestTest.php b/tests/Message/ClientTokenRequestTest.php
index f0a04ef..c517168 100644
--- a/tests/Message/ClientTokenRequestTest.php
+++ b/tests/Message/ClientTokenRequestTest.php
@@ -12,7 +12,7 @@ class ClientTokenRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/ClientTokenResponseTest.php b/tests/Message/ClientTokenResponseTest.php
index aa0c40c..e4d54ec 100644
--- a/tests/Message/ClientTokenResponseTest.php
+++ b/tests/Message/ClientTokenResponseTest.php
@@ -12,7 +12,7 @@ class ClientTokenResponseTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/CreateCustomerRequestTest.php b/tests/Message/CreateCustomerRequestTest.php
index c36f1b5..185bd95 100644
--- a/tests/Message/CreateCustomerRequestTest.php
+++ b/tests/Message/CreateCustomerRequestTest.php
@@ -12,7 +12,7 @@ class CreateCustomerRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/CreateMerchantAccountRequestTest.php b/tests/Message/CreateMerchantAccountRequestTest.php
index 06900c6..63aeede 100644
--- a/tests/Message/CreateMerchantAccountRequestTest.php
+++ b/tests/Message/CreateMerchantAccountRequestTest.php
@@ -13,7 +13,7 @@ class CreateMerchantAccountRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/CustomerResponseTest.php b/tests/Message/CustomerResponseTest.php
index 38ecd5e..b2f20fa 100644
--- a/tests/Message/CustomerResponseTest.php
+++ b/tests/Message/CustomerResponseTest.php
@@ -15,7 +15,7 @@ class CustomerResponseTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/DeleteCustomerRequestTest.php b/tests/Message/DeleteCustomerRequestTest.php
index 1dc4575..d5c62c3 100644
--- a/tests/Message/DeleteCustomerRequestTest.php
+++ b/tests/Message/DeleteCustomerRequestTest.php
@@ -12,7 +12,7 @@ class DeleteCustomerRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/DeletePaymentMethodRequestTest.php b/tests/Message/DeletePaymentMethodRequestTest.php
index cd80c41..3eeebdf 100644
--- a/tests/Message/DeletePaymentMethodRequestTest.php
+++ b/tests/Message/DeletePaymentMethodRequestTest.php
@@ -12,7 +12,7 @@ class DeletePaymentMethodRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->request = new DeletePaymentMethodRequest($this->getHttpClient(), $this->getHttpRequest(), Configuration::gateway());
         $this->request->initialize(
diff --git a/tests/Message/FindCustomerRequestTest.php b/tests/Message/FindCustomerRequestTest.php
index c51d819..b8c4241 100644
--- a/tests/Message/FindCustomerRequestTest.php
+++ b/tests/Message/FindCustomerRequestTest.php
@@ -10,7 +10,7 @@ class FindCustomerRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/FindRequestTest.php b/tests/Message/FindRequestTest.php
index 64e7356..3107b7f 100644
--- a/tests/Message/FindRequestTest.php
+++ b/tests/Message/FindRequestTest.php
@@ -12,7 +12,7 @@ class FindRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/PlanRequestTest.php b/tests/Message/PlanRequestTest.php
index b1f077f..4559ff3 100644
--- a/tests/Message/PlanRequestTest.php
+++ b/tests/Message/PlanRequestTest.php
@@ -15,7 +15,7 @@ class PlanRequestTest extends TestCase
     /** @var PlanRequest */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/PlanResponseTest.php b/tests/Message/PlanResponseTest.php
index 550a84c..4782eea 100644
--- a/tests/Message/PlanResponseTest.php
+++ b/tests/Message/PlanResponseTest.php
@@ -16,7 +16,7 @@ class PlanResponseTest extends TestCase
     /** @var  PlanRequest */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/PurchaseRequestTest.php b/tests/Message/PurchaseRequestTest.php
index 9e01d19..ca09ab1 100644
--- a/tests/Message/PurchaseRequestTest.php
+++ b/tests/Message/PurchaseRequestTest.php
@@ -12,7 +12,7 @@ class PurchaseRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/RefundRequestTest.php b/tests/Message/RefundRequestTest.php
index 42e3d67..c5d12f4 100644
--- a/tests/Message/RefundRequestTest.php
+++ b/tests/Message/RefundRequestTest.php
@@ -12,7 +12,7 @@ class RefundRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/ReleaseFromEscrowRequestTest.php b/tests/Message/ReleaseFromEscrowRequestTest.php
index cb06d1f..1721310 100644
--- a/tests/Message/ReleaseFromEscrowRequestTest.php
+++ b/tests/Message/ReleaseFromEscrowRequestTest.php
@@ -12,7 +12,7 @@ class ReleaseFromEscrowRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/ResponseTest.php b/tests/Message/ResponseTest.php
index 1a5c7b9..36702be 100644
--- a/tests/Message/ResponseTest.php
+++ b/tests/Message/ResponseTest.php
@@ -14,7 +14,7 @@ class ResponseTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/SubscriptionResponseTest.php b/tests/Message/SubscriptionResponseTest.php
index a3818e7..77c8c11 100644
--- a/tests/Message/SubscriptionResponseTest.php
+++ b/tests/Message/SubscriptionResponseTest.php
@@ -16,7 +16,7 @@ class SubscriptionResponseTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/UpdateCustomerRequestTest.php b/tests/Message/UpdateCustomerRequestTest.php
index 46badf7..f0c100d 100644
--- a/tests/Message/UpdateCustomerRequestTest.php
+++ b/tests/Message/UpdateCustomerRequestTest.php
@@ -12,7 +12,7 @@ class UpdateCustomerRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/UpdateMerchantAccountRequestTest.php b/tests/Message/UpdateMerchantAccountRequestTest.php
index 56a4c0e..4b71e8d 100644
--- a/tests/Message/UpdateMerchantAccountRequestTest.php
+++ b/tests/Message/UpdateMerchantAccountRequestTest.php
@@ -13,7 +13,7 @@ class UpdateMerchantAccountRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Message/UpdatePaymentMethodRequestTest.php b/tests/Message/UpdatePaymentMethodRequestTest.php
index fd6f59b..df40081 100644
--- a/tests/Message/UpdatePaymentMethodRequestTest.php
+++ b/tests/Message/UpdatePaymentMethodRequestTest.php
@@ -12,7 +12,7 @@ class UpdatePaymentMethodRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->request = new UpdatePaymentMethodRequest($this->getHttpClient(), $this->getHttpRequest(), Configuration::gateway());
     }
diff --git a/tests/Message/VoidRequestTest.php b/tests/Message/VoidRequestTest.php
index 6a9b51b..57a6c73 100644
--- a/tests/Message/VoidRequestTest.php
+++ b/tests/Message/VoidRequestTest.php
@@ -12,7 +12,7 @@ class VoidRequestTest extends TestCase
      */
     private $request;
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();