Disclosed are various embodiments for evaluating an application under development through use of a viewer application executing in a computer. The computer retrieves an application package comprising code for a target application to be evaluated in the computer. The code for the target application is stored in a memory of the computer accessible to the viewer application. The code for the target application is stored without installing the target application as a stand-alone application on the computer. Code of the viewer application is executed in order to execute the stored code for the target application for evaluation. Executing the stored code of the target application executes the target application within the execution of the viewer application.