diff --git a/sources/Composer/iTopComposer.php b/sources/Composer/iTopComposer.php
index c759d9ed0..0f5f0e77a 100644
--- a/sources/Composer/iTopComposer.php
+++ b/sources/Composer/iTopComposer.php
@@ -27,6 +27,8 @@ use RecursiveIteratorIterator;
 
 class iTopComposer
 {
+	const TEST_DIR_REGEXP = '/^[tT]ests?$/';
+
 	/**
 	 * @return array List of all subdirs of /lib that are {@see IsTestDir}.
 	 *              Warning : each path contains slashes (meaning on Windows you'll get eg `C:/Dev/wamp64/www/itop-27/lib/goaop/framework/tests`)
@@ -60,9 +62,9 @@ class iTopComposer
 		return $aAllTestDirs;
 	}
 	
-	private function IsTestDir($sDirName)
+	public static function IsTestDir($sDirName)
 	{
-		return preg_match('/^[tT]ests?$/', $sDirName);
+		return preg_match(self::TEST_DIR_REGEXP, $sDirName);
 	}
 
 	/**
diff --git a/test/application/composer/iTopComposerTest.php b/test/application/composer/iTopComposerTest.php
index 2d7ef86ee..159714618 100644
--- a/test/application/composer/iTopComposerTest.php
+++ b/test/application/composer/iTopComposerTest.php
@@ -54,10 +54,16 @@ class iTopComposerTest extends ItopTestCase
 
 		$this->assertTrue(is_array($aDirs));
 
+		$aDeniedDirWrongFormat = [];
 		foreach ($aDirs as $sDir)
 		{
-			$this->assertRegExp('#[tT]ests?/?$#', $sDir);
+			if (false === iTopComposer::IsTestDir($sDir)) {
+				$aDeniedDirWrongFormat[] = $sDir;
+			}
 		}
+
+		$this->assertEmpty($aDeniedDirWrongFormat,
+			'There are elements in \Combodo\iTop\Composer\iTopComposer::ListDeniedTestDir that are not test dirs :'.var_export($aDeniedDirWrongFormat, true));
 	}
 
 	public function testListAllowedTestDir()
@@ -100,9 +106,11 @@ class iTopComposerTest extends ItopTestCase
 		$aMissing = array_diff($aExistingDirs, $aAllowedAndDeniedDirs);
 		$aExtra = array_diff($aAllowedAndDeniedDirs, $aExistingDirs);
 
-		$this->assertEmpty($aMissing, "The iTop instance running this test has matching directories That must be either in the allowed or in the denied list:".var_export($aMissing, true));
-
+		$this->assertEmpty(
+			$aMissing,
+			'Test dirs exists in /lib !'."\n"
+				.'  They must be declared either in the allowed or denied list in '.iTopComposer::class." (see N°2651).\n"
+				.'  List of dirs:'."\n".var_export($aMissing, true)
+		);
 	}
-
-
 }