To effectively test Drag and Drop functionality in Selenium IDE, it is necessary to simulate the behavior. Here are some steps you can take to achieve this:
1) Utilize the mouseDownAt(locator, coordString) command to press down on the left mouse button and hold it.
2) It is often helpful to wait for a reaction or data to be loaded in the DOM before proceeding. Consider adding a small pause to ensure that the object is properly "captured" by the mouse for dragging (remember that test running times may differ from a human's interaction with a website).
3) Use the mouseMoveAt(locator, coordinate) command to drag the selected item to its desired location.
4) Release the mouse button by using the mouseUpAt(locator, coordString) command to complete the drag and drop process.
Experiment with varying mouse speeds by adjusting the values and incorporating pauses at different points in your test script. Modify locators as needed based on the specifics of your project application.
Consider adding setMouseSpeed(pixels) at the beginning of these actions to slow down the mouse movement for better control during dragging. Remember to reset the mouse speed back to its default value (10 pixels per step) at the end of the sequence, unless otherwise specified for specific scenarios.