Question

Is it possible to define some test data, for a java program, in a way that enables it to be easily human readable and programmatically parsable into the relevant function calls and data elements.
If it is impossible do achieve in Java I’m open to using Scala for this. The code under test is java code and this will not be ported to Scala.

    interface someInterface {
        class X {
            // the member variables will always either 
            // be enums or intrinsic types 
            private int a;
            public int a() { return this.a; };
            public void a(int a) {this.a = a; };

            private double b;
            public double b() { return this.b; };
            public void b(double b) {this.b = b; };

            private String c;
            public String c() { return this.c; };
            public void c(String c) {this.c = c; };
        }

        enum A {
            A_1,
            A_2
        }
        class Y {
            // assume setters and getters as per X above
            private A a;
            private double b;
            private String c;
            private Z[] z;
        }
        class Z {
            private int a;
            private double b;
            private String c;
        }

        Y function1(X x, String s);
    }

    public void boo() {
        String[] testData = {
            /* how can I specify this array so that 
               coo(...) can be called as below
               would I be better off defining this 
               test code in Scala?
               the classes and interfaces above: 
               someInterface, A, X, Y and Z are in Java 
               and will not be ported to Scala */
        };
        coo(testData);
    }

    public void coo(String[] testData) {
        /* this function will know how to:
               a) parse testData
               b) use reflection to call 
                  someInterface.functionXXX with parameters
                  as specified in testData
               c) construct the return result as specified 
                  in testData and compare against actual 
                  return result */
    }   
}

Answer 1

You can use JUnit 4 for this and run with a Parameterized class.

Create a test class like this:

@RunWith(Parameterized.class)
public class MyTest
{
      private String s;
      private SomeInterface.X x;
      private SomeInterface someInterface;

      @Parameters
      public static Collection<Object[]> prepareData()
      {
            Collection<Object[]> args = new ArrayList<Object[]>();

            args.add(new Object[]{"org.some.thing.Impl",  1, 2.6,"Hello", "World"});
            args.add(new Object[]{"org.some.thing.Impl",  2, 2.7,"Goodbye", "World"});
            args.add(new Object[]{"org.some.thing.Impl",  3, 2.8,"Hello", "Universe"});
            args.add(new Object[]{"org.some.thing.Impl2", 4, 2.9,"Goodbye", "Universe"});

            return args;        
      }

      public MyTest(Object[] args)
      {
            String someInterfaceImplementation = args[0].toString();

            someInterface = null;

            int a = (Integer) args[1];
            double b = (Double) args[2];
            String c = (String) args[3];

            s = (String) args[4];

            x = new SomeInterface.X();
            x.a(a);
            x.b(b);
            x.c(c);
      }

      @Test
      public void testSomething()
      {
            someInterface.function1(x, s);
      }
 }

Explenation:

@RunWith(Parameterized.class) tells the JUnit framework to run ask the test class for parameters, and run all the test in the class with those parametrs.
It expects a Collection of Object[]. Each Object[] is passed via reflection to the constructor of this class.

prepareData – provides all the scenarios you want to test.

MyTest(Object[] args) populates the members of this class before running all the tests on a specific parameter set. Important to note that the ‘someInterface` is initialized only once – for each parameter set. If you add more tests for the same parameter set, you might need to re-initialize it.

testSomething() runs your test. It will run one time per Object[] that prepareData provides. And it is guaranteed to run after the MyTest(Object[] args) has been executed (duh, like you have any alternative here)