After you add a data source to the Data Source Library, you can test the data source to make sure that it is working properly. There are two ways to do this: Either you can show the data in the Data Source Details task pane, or you can drag the data source onto a page. If the data is displayed as expected either on the page or in the task pane, the data source is configured properly.
What do you want to do?
Show data in the Data Source Details task pane
The Data Source Details task pane displays data from one record at a time in your data source. At the top of the task pane, you can see the total number of records in the data source and also which record is currently displayed.
If the Data Source Library isn't visible, on the Task Panes menu, click Data Source Library.
In the Data Source Library task pane, click the data source that you want to test, and then click Show Data.
If the data in the Data Source Details task pane appears as expected, your data source is configured properly.A SharePoint Announcements list as it appears in the Data Source Details task pane
If your data source connection includes multiple records, you can view data in other records by clicking one of the arrows near the top of the data list.
Test a data source by dragging it onto the page
You can also quickly test a data source by creating a Data View of that data source. When you drag a data source onto a page, the result is a default view of the data, in which the first five fields in your data source appear in each row in a basic table. If the first five fields appear with the corresponding data, the data source is configured properly.
Data Views are based on Microsoft ASP.NET 2.0 technology. To create a Data View, you must start with an ASP.NET page (.aspx file).
On the File menu, click New.
In the New dialog box, on the Page tab, click General, then click ASPX, and then click OK.
A new page with a FORM tag opens.
On the Task Panes menu, click Data Source Library.
In the Data Source Library task pane, locate your data source, and then drag it onto the page.
A Data View is displayed on your page. If the data in the Data View appears as expected, your data source is configured properly.