diff --git a/.gitignore b/.gitignore
index a6d5a82..6d847b0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@
 composer.lock
 composer.phar
 tests.log
+/.phpunit.result.cache
diff --git a/composer.json b/composer.json
index d5f8693..05d2633 100644
--- a/composer.json
+++ b/composer.json
@@ -26,7 +26,7 @@
         "ethanhann/redis-raw": "v1.x-dev"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.0",
+        "phpunit/phpunit": "^8.0",
         "mockery/mockery": "^0.9.9",
         "predis/predis": "^1.1",
         "friendsofphp/php-cs-fixer": "^2.2",
diff --git a/tests/RediSearch/Aggregate/AggregationResultTest.php b/tests/RediSearch/Aggregate/AggregationResultTest.php
index dd9be38..07bef94 100644
--- a/tests/RediSearch/Aggregate/AggregationResultTest.php
+++ b/tests/RediSearch/Aggregate/AggregationResultTest.php
@@ -14,7 +14,7 @@ class AggregationResultTest extends RediSearchTestCase
     protected $subject;
     protected $expectedDocuments;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->expectedDocuments = [
             ['title' => 'part1'],
diff --git a/tests/RediSearch/Aggregate/BuilderTest.php b/tests/RediSearch/Aggregate/BuilderTest.php
index 4850b9d..a612e0e 100644
--- a/tests/RediSearch/Aggregate/BuilderTest.php
+++ b/tests/RediSearch/Aggregate/BuilderTest.php
@@ -19,7 +19,7 @@ class BuilderTest extends RediSearchTestCase
     private $expectedResult3;
     private $expectedResult4;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->indexName = 'AggregateBuilderTest';
         $index = (new TestIndex($this->redisClient, $this->indexName))
@@ -67,7 +67,7 @@ public function setUp()
         $this->subject = (new Builder($this->redisClient, $this->indexName));
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         $this->redisClient->flushAll();
     }
diff --git a/tests/RediSearch/Fields/TextFieldTest.php b/tests/RediSearch/Fields/TextFieldTest.php
index 11957b0..d48c183 100644
--- a/tests/RediSearch/Fields/TextFieldTest.php
+++ b/tests/RediSearch/Fields/TextFieldTest.php
@@ -18,7 +18,7 @@ class TextFieldTest extends TestCase
     /** @var float */
     private $defaultWeight = 1.0;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->subject = new TextField($this->fieldName);
     }
diff --git a/tests/RediSearch/IndexTest.php b/tests/RediSearch/IndexTest.php
index fc586d8..9de6d7c 100644
--- a/tests/RediSearch/IndexTest.php
+++ b/tests/RediSearch/IndexTest.php
@@ -29,7 +29,7 @@ class IndexTest extends RediSearchTestCase
     /** @var IndexInterface */
     private $subject;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->indexName = 'ClientTest';
         $this->subject = (new TestIndex($this->redisClient, $this->indexName))
@@ -43,7 +43,7 @@ public function setUp()
         $this->logger->debug('setUp...');
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         $this->redisClient->flushAll();
     }
diff --git a/tests/RediSearch/Query/BuilderTest.php b/tests/RediSearch/Query/BuilderTest.php
index 79a1ab7..f99e837 100644
--- a/tests/RediSearch/Query/BuilderTest.php
+++ b/tests/RediSearch/Query/BuilderTest.php
@@ -14,7 +14,7 @@ class BuilderTest extends RediSearchTestCase
     private $expectedResult1;
     private $expectedResult2;
     private $expectedResult3;
-    public function setUp()
+    public function setUp(): void
     {
         $this->indexName = 'QueryBuilderTest';
         $index = (new TestIndex($this->redisClient, $this->indexName))
@@ -54,7 +54,7 @@ public function setUp()
         $this->subject = (new Builder($this->redisClient, $this->indexName));
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         $this->redisClient->flushAll();
     }
diff --git a/tests/RediSearch/RuntimeConfigurationTest.php b/tests/RediSearch/RuntimeConfigurationTest.php
index e498f53..cb9ec40 100644
--- a/tests/RediSearch/RuntimeConfigurationTest.php
+++ b/tests/RediSearch/RuntimeConfigurationTest.php
@@ -10,12 +10,12 @@ class RuntimeConfigurationTest extends RediSearchTestCase
     /** @var RuntimeConfiguration */
     private $subject;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->subject = (new RuntimeConfiguration($this->redisClient, 'foo'));
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         $this->redisClient->flushAll();
     }
diff --git a/tests/RediSearch/SuggestionTest.php b/tests/RediSearch/SuggestionTest.php
index dfa442c..6134f21 100644
--- a/tests/RediSearch/SuggestionTest.php
+++ b/tests/RediSearch/SuggestionTest.php
@@ -10,12 +10,12 @@ class SuggestionTest extends RediSearchTestCase
     /** @var Suggestion */
     private $subject;
 
-    public function setUp()
+    public function setUp(): void
     {
         $this->subject = (new Suggestion($this->redisClient, 'foo'));
     }
 
-    public function tearDown()
+    public function tearDown(): void
     {
         $this->redisClient->flushAll();
     }