Replacement of assertEquals() to assertSame()

tests/model/DbExprTest.php

@@ -18,6 +18,6 @@ class DbExprTest extends PHPUnit_Framework_TestCase
     {
         $expr = new DbExpr('THIS IS SQL EXPRESSION');
         $str = (string) $expr;
-        $this->assertEquals('THIS IS SQL EXPRESSION', $str);
+        $this->assertSame('THIS IS SQL EXPRESSION', $str);
     }
 }