diff --git a/composer.json b/composer.json
index 93414b9..b5a8fc9 100644
--- a/composer.json
+++ b/composer.json
@@ -38,7 +38,7 @@
         "friendsofphp/php-cs-fixer": "^2.3",
         "johnkary/phpunit-speedtrap": "^3.2",
         "phlak/coding-standards": "^1.1",
-        "phpunit/phpunit": "^9.1",
+        "phpunit/phpunit": "^8.0 || ^9.0",
         "psy/psysh": "^0.10",
         "symfony/var-dumper": "^5.0",
         "vimeo/psalm": "^3.6"
diff --git a/tests/Controllers/SearchControllerTest.php b/tests/Controllers/SearchControllerTest.php
index 10b3ba4..bad95c4 100644
--- a/tests/Controllers/SearchControllerTest.php
+++ b/tests/Controllers/SearchControllerTest.php
@@ -30,7 +30,7 @@ class SearchControllerTest extends TestCase
 
         $this->assertInstanceOf(ResponseInterface::class, $response);
         $this->assertEquals(200, $response->getStatusCode());
-        $this->assertDoesNotMatchRegularExpression('/No results found/', (string) $response->getBody());
+        $this->assertStringNotContainsString('No results found', (string) $response->getBody());
     }
 
     public function test_it_returns_no_results_found_when_there_are_no_results(): void
@@ -49,7 +49,7 @@ class SearchControllerTest extends TestCase
 
         $this->assertInstanceOf(ResponseInterface::class, $response);
         $this->assertEquals(200, $response->getStatusCode());
-        $this->assertMatchesRegularExpression('/No results found/', (string) $response->getBody());
+        $this->assertStringContainsString('No results found', (string) $response->getBody());
     }
 
     public function test_it_returns_no_results_found_for_a_blank_search(): void
@@ -68,6 +68,6 @@ class SearchControllerTest extends TestCase
 
         $this->assertInstanceOf(ResponseInterface::class, $response);
         $this->assertEquals(200, $response->getStatusCode());
-        $this->assertMatchesRegularExpression('/No results found/', (string) $response->getBody());
+        $this->assertStringContainsString('No results found', (string) $response->getBody());
     }
 }
diff --git a/tests/TemporaryFileTest.php b/tests/TemporaryFileTest.php
index 5c2c7c0..3273ef0 100644
--- a/tests/TemporaryFileTest.php
+++ b/tests/TemporaryFileTest.php
@@ -33,6 +33,6 @@ class TemporaryFileTest extends TestCase
 
         unset($tempFile);
 
-        $this->assertFileDoesNotExist($filePath);
+        $this->assertFalse(is_file($filePath));
     }
 }