A test domain configuration module generates graphical user interfaces for identifying information about desired tests such as data types and domain configurations, and collects information used by other modules to generate tests. The identified information may include, for example, an abstract syntax, a static semantic, max counts on instances of data types, or costs of field accesses or data types for max path costs or max expression costs. A test input generator, generates test input for the identified and configured data types. In one case, the generated test inputs are generated as tree data structures. A predicate determines whether a generated test input follows semantic conditions. A test input evaluator counts instances of data types in, sums paths through, or sums total costs of, the generated test inputs. A test acceptance module saves test inputs acceptable to the predicate and the test input evaluator.