...
Click on Setup menu and select Import/Export Test option.
You will be landed on Import Export Test screen.
Select application from the drop down or you can simply write the application name in the search field whose you want to export test cases. Once you select the application, created module and test cases in selected application along with business component will populate in right pane of the window.
Expand modules and select test case whose you want to export. You can select multiple test case.
Note :- Here if a test contains business component will export automatically along with test cases. you need not select business component separately. Suppose you are exporting Create Contacts test case and this test is using business component Login to Salesforce will export automatically along test case Create Contacts.
Click on Export button.
Enter name by which you want to identify exported test's file. Click on Start button. File will be downloaded in .bqo format and a unique number is appended in the file name. Entire data in file name will be in completely encrypted format.
...