diff --git a/api/tests/api/WorkingHours/BrowseWorkingHoursCest.php b/api/tests/api/WorkingHours/BrowseWorkingHoursCest.php
index 65a5d1b..823495f 100644
--- a/api/tests/api/WorkingHours/BrowseWorkingHoursCest.php
+++ b/api/tests/api/WorkingHours/BrowseWorkingHoursCest.php
@@ -3,6 +3,7 @@
 namespace TorstenHettstedt\TimekeepingApi\Tests\Api\WorkingHours;
 
 use ApiTester;
+use Codeception\Example;
 use Codeception\Util\HttpCode;
 use Helper\Api;
 
@@ -20,16 +21,54 @@ class BrowseWorkingHoursCest
         $I->seeHttpHeader('Access-Control-Max-Age');
     }
 
+    public function validWorkingHoursFilterProvider(): array
+    {
+        return [
+            [[null]],
+            [['start-date' => '2020-01-01', 'end-date' => '2020-01-08']],
+            [['start-date' => '2020-01-01', 'end-date' => '2020-04-30']],
+            [['start-date' => '2020-04-01', 'end-date' => '2020-04-30']],
+        ];
+    }
+
     /**
      * @param ApiTester $I
+     * @param Example   $example
+     *                          
+     * @dataProvider validWorkingHoursFilterProvider
      */
-    public function browseWorkingHours(ApiTester $I): void
+    public function browseWorkingHours(ApiTester $I, Example $example): void
     {
         $I->haveHttpHeader('Origin', Api::TEST_ORIGIN);
-        $I->sendGet('/working-hours');
+        $I->sendGet('/working-hours', $example[0]);
         $I->seeResponseCodeIs(HttpCode::OK);
         $I->canSeeHttpHeader('Access-Control-Allow-Origin', Api::TEST_ORIGIN);
         $I->seeResponseIsJson();
         $I->seeResponseMatchesJsonType(Api::WORKING_HOURS_JSON_FORMAT);
     }
+
+    public function invalidWorkingHoursFilterProvider(): array
+    {
+        return [
+            ['2020-11-31'],
+            ['2020-11'],
+            ['2020'],
+        ];
+    }
+
+    /**
+     * @param ApiTester $I
+     * @param Example   $example
+     *
+     * @dataProvider invalidWorkingHoursFilterProvider
+     */
+    public function browseWorkingHoursWithWrongFilterDate(ApiTester $I, Example $example): void
+    {
+        $I->haveHttpHeader('Origin', Api::TEST_ORIGIN);
+        $I->sendGet('/working-hours', ['start-date' => $example[0]]);
+        $I->seeResponseCodeIs(HttpCode::BAD_REQUEST);
+        $I->canSeeHttpHeader('Access-Control-Allow-Origin', Api::TEST_ORIGIN);
+        $I->seeResponseIsJson();
+        $I->seeResponseMatchesJsonType(Api::ERROR_JSON_FORMAT);
+    }
 }