Tcases: A Model-Based Test Case Generator

What's New?

What Does It Do?

Tcases is a tool for designing tests. It doesn't matter what kind of system you are testing. Nor does it matter what level of the system you are testing -- unit, subsystem, or full system. You can use Tcases to design your tests in any of these situations. With Tcases, you define the input space for your system-under-test and the level of coverage that you want. Then Tcases generates a minimal set of test cases that meets your requirements.

Tcases is primarily a tool for black-box test design. For such tests, the concept of "coverage" is different from structural testing critieria such as line coverage, branch converage, etc. Instead, Tcases is guided by coverage of the input space of your system.

Tcases gives you a way to define the input space for your system in a form that is concise but comprehensive. Then Tcases allows you to control the number of test cases in your sample subset by specifying the level of coverage you want. You can start with a basic level of coverage, and Tcases will generate a small set of test cases that touches every significant element of the input space. Then you can improve your tests by selectively adding coverage in specific high-risk areas. For example, you can specify pairwise coverage or higher-order combinations of selected input variables.

How Does It Work?

First, you create a system input definition, a document that defines your system as a set of functions. For each system function, the system input definition defines the variables that characterize the function input space. If you are testing a Web service API, you can even generate a system input definition automatically from an OpenAPI spec.

Then, you can create a generator definition. That's another document that defines the coverage you want for each system function. The generator definition is optional. You can skip this step and still get a basic level of coverage.

Finally, you run Tcases. Tcases is a Java program that you can run from the command line or using the Tcases Maven Plugin. The command line version of Tcases comes with built-in support for running using a shell script or an ant target. Using your input definition and your generator definition, Tcases generates a system test definition. The system test definition is a document that lists, for each system function, a set of test cases that provides the specified level of coverage. Each test case defines a specific value for every function input variable. Tcases generates not only valid input values that define successful test cases but also invalid values for the tests cases that are needed to verify expected error handling.

Of course, the system test definition is not something you can execute directly. (Unless it was derived automatically from an OpenAPI spec!) But it follows a well-defined schema, which means you can use a variety of transformation tools to convert it into a form that is suitable for testing your system. For example, Tcases comes with a built-in transformer that converts a system test definition into a Java source code template for a JUnit or TestNG test class.

Get Started!


Thanks to the following people, who have contributed significant improvements to Tcases.