CodeFirst:The specified named connection is either not found in the configuration

I create a Test Project to test my queries , every thing goes okay except when i try to test a method which use Entity Connection ,I get the following exception :

The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid.

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My connection string in app.config in the TestQuery Project which is my startup project is:

 <connectionStrings>
    <add name="DataLayer.Context" connectionString="Data Source=.;Initial Catalog=TestQ;Integrated Security=True" providerName="System.Data.SqlClient"/>
 </connectionStrings>

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All the methods which use linq to entity works just fine and brings the data except this one ?