fix tests failed in exports

src/Bundle/ChillMainBundle/Test/Export/AbstractAggregatorTest.php

@@ -166,6 +166,7 @@ abstract class AbstractAggregatorTest extends KernelTestCase
         $this->assertContainsOnly(
             'string',
             $queryKeys,
+            true,
             'test that the query keys returned by `getQueryKeys` are only strings'
         );
         $this->assertGreaterThanOrEqual(

src/Bundle/ChillMainBundle/Test/Export/AbstractExportTest.php

@@ -140,6 +140,7 @@ abstract class AbstractExportTest extends WebTestCase
         $this->assertContainsOnly(
             'string',
             $formattersTypes,
+            true,
             'Test that the method `getAllowedFormattersTypes` returns an array of string'
         );
     }
@@ -174,6 +175,7 @@ abstract class AbstractExportTest extends WebTestCase
         $this->assertContainsOnly(
             'string',
             $queryKeys,
+            true,
             'test that the query keys returned by `getQueryKeys` are only strings'
         );
         $this->assertGreaterThanOrEqual(
@@ -395,6 +397,7 @@ abstract class AbstractExportTest extends WebTestCase
             $this->assertContainsOnly(
                 'string',
                 $export->supportsModifiers(),
+                true,
                 'Test that the `supportsModifiers` method returns only strings'
             );
         } elseif ($query instanceof NativeQuery) {