diff --git a/tests/Encoder/JsonEncoderTest.php b/tests/Encoder/JsonEncoderTest.php
index 52462ab..bbcf7b8 100644
--- a/tests/Encoder/JsonEncoderTest.php
+++ b/tests/Encoder/JsonEncoderTest.php
@@ -18,7 +18,7 @@ class JsonEncoderTest extends TestCase
      *
      * @return void
      */
-    public function testEncode()
+    public function testEncode(): void
     {
         $encoder = new JsonEncoder();
         $actual = $encoder->encode(['key' => 'value']);
diff --git a/tests/Transformer/ErrorDetailsTransformerTest.php b/tests/Transformer/ErrorDetailsTransformerTest.php
index 89ae0c7..8e044cc 100644
--- a/tests/Transformer/ErrorDetailsTransformerTest.php
+++ b/tests/Transformer/ErrorDetailsTransformerTest.php
@@ -18,7 +18,7 @@ class ErrorDetailsTransformerTest extends TestCase
      *
      * @return void
      */
-    public function testTransform()
+    public function testTransform(): void
     {
         $transformer = new ErrorDetailsResultTransformer();
 
@@ -44,12 +44,4 @@ public function testTransform()
 
         static::assertSame($exptected, $actual);
     }
-
-    /**
-     * Test.
-     */
-    public function testInvalidEncoding(): void
-    {
-        $this->assertTrue(true);
-    }
 }