Testing Java Applications

Derek Jones and Rainer Mauth

When granularity [of components] becomes so tiny [as when testing Java applications], the problems of integration testing are enormous," says Jeffrey Voas, chief scientist with Reliable Software Technologies (Sterling, VA), a software research and consulting company.

Testing Java applications is difficult because developers are forced to test applets on each configuration that they plan to support. This includes the different implementations of Java virt ual machines (VMs) -- browsers as well as compilers. In addition, because Java doesn't allow a testing class to gain access to private data and methods, developers must either add test methods to a cla ss or change private classes to public classes. "Both of these options might modify the class so that some faults are not found," notes Jeffrey Payne, president of Reliable Software Technologies.

Another issue is that Java's built-in security mechanisms make the testing of applets trickier. Test tools can't easily write results to disk due to security constraints. "In addition, testing must be performed both inside of and through any corporate firewalls to ensure that applets will operate correctly," Payne adds.

To specifically address the problems of VM diversity, JavaSoft has launched the 100% Pure Java Certification program, which requires Java developers to ensure that applications are portable. SunTest, a subsidiary of Sun Microsystems, has introduced a suite of tools that helps developers not only gain certification but also perform overall quality testing.

JavaPureCheck checks that class files are indeed portable. It measures specified classes against a rule base. Classes that don't meet these rules are flagged, along with the construct that violates one of the portability rules. These errors and explanations are kept in a database that creates reports. You can download this tool for free from the SunTest Web site.

JavaSpin tests Java applications at run time. It's a low-end dynamic test tool that exercises a program through its GUI.

JavaScope is a coverage-analysis tool that includes method, branch, logical, and relational coverage (i.e., it looks at the usage of Boolean operators, which is effective for detecting boundary-condition failures). The current release does not support statement coverage, however.

JavaStar is a GUI record and playback tool. It includes a scripting language and compares the behavior of the program under test with the expected behavior.

JavaSpec uses the formal specifications of an API to automatically generate test programs. Developers can verify that an implementation of an API follows its written specification. JavaSpec was selected to create and maintain the entire Java API test suite for JavaSoft.