diff --git a/phpunit.xml b/phpunit.xml
index 03c0f13..002a138 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -19,12 +19,6 @@
       <directory suffix="Test.php">tests/Functional/</directory>
       <directory suffix="Test.php">tests/BC/</directory>
     </testsuite>
-    <testsuite name="unit">
-      <directory suffix="Test.php">tests/Unit/</directory>
-    </testsuite>
-    <testsuite name="functional">
-      <directory suffix="Test.php">tests/Functional/</directory>
-    </testsuite>
   </testsuites>
   <source>
     <include>
diff --git a/src/V1/Factory.php b/src/V1/Factory.php
index 8d99636..f1bab75 100644
--- a/src/V1/Factory.php
+++ b/src/V1/Factory.php
@@ -67,7 +67,11 @@ public function make($name, array $args = []): Accessable
         $object = $class->newInstanceArgs($args);
 
         if (! $object instanceof Accessable) {
-            throw new FactoryException($this->classes[$name] . ' must be instance of `Art4\JsonApiClient\Accessable`');
+            throw new FactoryException(sprintf(
+                '%s must be instance of `%s`',
+                $this->classes[$name],
+                Accessable::class
+            ));
         }
 
         return $object;
diff --git a/tests/Unit/V1/FactoryTest.php b/tests/Unit/V1/FactoryTest.php
index a96aaef..5d1b6b0 100644
--- a/tests/Unit/V1/FactoryTest.php
+++ b/tests/Unit/V1/FactoryTest.php
@@ -13,6 +13,7 @@
 use Art4\JsonApiClient\V1\Factory;
 use Art4\JsonApiClient\V1\ResourceNull;
 use PHPUnit\Framework\TestCase;
+use stdClass;
 
 class FactoryTest extends TestCase
 {
@@ -49,4 +50,18 @@ public function testMakeAnUndefindedClassThrowsException()
 
         $class = $factory->make('NotExistent');
     }
+
+    public function testMakeWithClassNotImplementingAccessableThrowsException()
+    {
+        $factory = new Factory([
+            'Default' => stdClass::class,
+        ]);
+
+        $this->expectException(FactoryException::class);
+        $this->expectExceptionMessage(
+            'stdClass must be instance of `Art4\JsonApiClient\Accessable`'
+        );
+
+        $class = $factory->make('Default');
+    }
 }