ACPT-860: Indexation time is calculated incorrectly

- Add unit tests coverage;

Author: adifucan

app/code/Magento/Indexer/Test/Unit/Console/Command/IndexerReindexCommandTest.php

@@ -130,6 +130,11 @@ public function testExecuteAll()
             self::STUB_INDEXER_NAME . ' index has been rebuilt successfully in',
             $actualValue
         );
+        $this->assertMatchesRegularExpression(
+            '/' . self::STUB_INDEXER_NAME
+            . ' index has been rebuilt successfully in (?:(?:([01]?\d|2[0-3]):)?([0-5]?\d):)?([0-5]?\d)/m',
+            $actualValue
+        );
     }
 
     /**