diff --git a/.circleci/config.yml b/.circleci/config.yml
index 371c526..6549dfb 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -1,6 +1,6 @@
 version: 2 # use CircleCI 2.0
 
-x-dockerbuild-7: &dockerbuild-7
+x-dockerbuild-phpdbg: &dockerbuild-phpdbg
   steps:
     - checkout
     - run: sudo docker-php-ext-install sockets
@@ -19,16 +19,28 @@ x-dockerbuild-5: &dockerbuild-5
     - run: composer lint
 
 jobs:
+  test-8.0:
+    <<: *dockerbuild-phpdbg
+    docker:
+      - image: circleci/php:8.0-node-browsers
+  test-7.4:
+    <<: *dockerbuild-phpdbg
+    docker:
+      - image: circleci/php:7.4-node-browsers
+  test-7.3:
+    <<: *dockerbuild-phpdbg
+    docker:
+      - image: circleci/php:7.3-node-browsers
   test-7.2:
-    <<: *dockerbuild-7
+    <<: *dockerbuild-phpdbg
     docker:
       - image: circleci/php:7.2-node-browsers
   test-7.1:
-    <<: *dockerbuild-7
+    <<: *dockerbuild-phpdbg
     docker:
       - image: circleci/php:7.1-node-browsers
   test-7.0:
-    <<: *dockerbuild-7
+    <<: *dockerbuild-phpdbg
     docker:
       - image: circleci/php:7.0-node-browsers
   test-5.6:
@@ -40,6 +52,9 @@ workflows:
   version: 2
   check_compile:
     jobs:
+      - test-8.0
+      - test-7.4
+      - test-7.3
       - test-7.2
       - test-7.1
       - test-7.0
diff --git a/composer.json b/composer.json
index 0879208..df52530 100644
--- a/composer.json
+++ b/composer.json
@@ -49,7 +49,7 @@
         "sort-packages": true
     },
     "require-dev": {
-        "phpunit/phpunit": "5.7.27",
+        "yoast/phpunit-polyfills": "^1.0.1",
         "squizlabs/php_codesniffer": "^3.3"
     },
     "scripts": {
diff --git a/tests/TestHelpers/CurlSpyTestCase.php b/tests/TestHelpers/CurlSpyTestCase.php
index 050afcf..09f6e2f 100644
--- a/tests/TestHelpers/CurlSpyTestCase.php
+++ b/tests/TestHelpers/CurlSpyTestCase.php
@@ -2,7 +2,7 @@
 
 namespace DataDog\TestHelpers;
 
-use PHPUnit\Framework\TestCase;
+use Yoast\PHPUnitPolyfills\TestCases\TestCase;
 
 $curlSpy = new CurlSpy();
 
@@ -11,13 +11,12 @@ class CurlSpyTestCase extends TestCase
     /**
      * Set up a spy object to capture calls to built in curl functions
      */
-    protected function setUp()
+    protected function set_up()
     {
         global $curlSpy;
 
         $curlSpy = new CurlSpy();
-
-        parent::setUp();
+        parent::set_up();
     }
 
     /**
diff --git a/tests/TestHelpers/SocketSpyTestCase.php b/tests/TestHelpers/SocketSpyTestCase.php
index 24b1514..7b85dda 100644
--- a/tests/TestHelpers/SocketSpyTestCase.php
+++ b/tests/TestHelpers/SocketSpyTestCase.php
@@ -3,7 +3,7 @@
 namespace DataDog\TestHelpers;
 
 use DataDog\DogStatsd;
-use PHPUnit\Framework\TestCase;
+use Yoast\PHPUnitPolyfills\TestCases\TestCase;
 
 /**
  * Making this variable global to this file is necessary for interacting with
@@ -24,13 +24,13 @@ class SocketSpyTestCase extends TestCase
     /**
      * Set up a spy object to capture calls to global built in socket functions
      */
-    protected function setUp()
+    protected function set_up()
     {
         global $socketSpy;
 
         $socketSpy = new SocketSpy();
 
-        parent::setUp();
+        parent::set_up();
     }
 
     /**
diff --git a/tests/UnitTests/BatchedDogStatsdTest.php b/tests/UnitTests/BatchedDogStatsdTest.php
index ae707de..7594d91 100644
--- a/tests/UnitTests/BatchedDogStatsdTest.php
+++ b/tests/UnitTests/BatchedDogStatsdTest.php
@@ -8,9 +8,9 @@
 
 class BatchedDogStatsdTest extends SocketSpyTestCase
 {
-    protected function setUp()
+    protected function set_up()
     {
-        parent::setUp();
+        parent::set_up();
 
         // Flush the buffer to reset state for next test
         BatchedDogStatsd::$maxBufferLength = 50;
diff --git a/tests/UnitTests/DogStatsd/SocketsTest.php b/tests/UnitTests/DogStatsd/SocketsTest.php
index f9443b4..ee7ce97 100644
--- a/tests/UnitTests/DogStatsd/SocketsTest.php
+++ b/tests/UnitTests/DogStatsd/SocketsTest.php
@@ -9,9 +9,9 @@
 
 class SocketsTest extends SocketSpyTestCase
 {
-    public function setUp()
+    public function set_up()
     {
-        parent::setUp();
+        parent::set_up();
 
         // Reset the stubs for mt_rand() and mt_getrandmax()
         global $mt_rand_stub_return_value;
diff --git a/tests/curl_and_error_log_function_stubs.php b/tests/curl_and_error_log_function_stubs.php
index 4d964a4..ebf7c64 100644
--- a/tests/curl_and_error_log_function_stubs.php
+++ b/tests/curl_and_error_log_function_stubs.php
@@ -24,7 +24,7 @@ function curl_init($url = null)
 
     $curlSpy->curlInitWasCalledWithArg($url);
 
-    $resource = fopen('/dev/null', 'r');
+    $resource = tmpfile();
 
     $curlSpy->curlInitDidReturn($resource);
 
diff --git a/tests/socket_function_stubs.php b/tests/socket_function_stubs.php
index cc2c7d7..554f877 100644
--- a/tests/socket_function_stubs.php
+++ b/tests/socket_function_stubs.php
@@ -29,7 +29,7 @@ function socket_create($domain, $type, $protocol)
 
     // A PHP resource of unimportance, useful primarily to assert that our stubs
     // of the global socket functions return or take a deterministic value.
-    $resource = fopen('/dev/null', 'r');
+    $resource = tmpfile();
 
     $socketSpy->socketCreateDidReturn($resource);