Microsoft Unit Tests - Data source cannot be found in the test configuration settings

I am trying to build Test class of data-driven unit tests in C#. I want to use 3 databases: one from SQL, one from Access and one from Excel. This is my app.config file:

    <?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="microsoft.visualstudio.testtools"
             type="Microsoft.VisualStudio.TestTools.UnitTesting.TestConfigurationSection, 
                   Microsoft.VisualStudio.QualityTools.UnitTestFramework, 
                   Version=10.0.0.0, 
                   Culture=neutral"/>
  </configSections>
  <connectionStrings>
    <add name="MyJetConn"
         connectionString="Provider=Microsoft.ACE.OLEDB.12.0;
                           Data Source=H:\SQA\CoolMath\CoolMath\Database1.accdb;
                           Persist Security Info=False;"
         providerName="System.Data.OleDb" />
    <add name="MyExcelConn"
         connectionString="Dsn=Excel Files;
                           dbq=H:\SQA\CoolMath\CoolMath\CoolMathExcelDataTable.xlsx;
                           defaultdir=.;
                           driverid=1046;
                           maxbuffersize=2048;
                           pagetimeout=5"
         providerName="System.Data.Odbc" />
    <add name="MSSQLConn"
         connectionString="Data Source=H:\SQA\CoolMath\CoolMath\SQLExpress;
                           Initial Catalog=MSSQLDB;
                           Integrated Security=SSPI;"
         providerName="System.Data.SqlClient" />
  </connectionStrings>
  <microsoft.visualstudio.testtools>
    <dataSources>
      <add name="MyJetDataSource"
           connectionString="MyJetConn"
           dataTableName="CoolMathAcessDataTable"
           dataAccessMethod="Sequential"/>
      <add name="MyExcelDataSource"
           connectionString="MyExcelConn"
           dataTableName="Sheet1$"
           dataAccessMethod="Sequential"/>
      <add name="MSSQLDataSource"
           connectionString="MSSQLConn"
           dataTableName="dbo.CoolMathDataTable"
      dataAccessMethod="Sequential"/>
    </dataSources>
  </microsoft.visualstudio.testtools>
</configuration>

When I try to run the tests, they all fail with the message: "Data source cannot be found in the test configuration settings". I can't see what am I doing wrong, perhaps it is the location of the databases? (they all in the same library as the code project and the XML file). Thank for all the helpers!