Package de.hsh.graja.modules.junit.api

Class StaticMethodChecker

  • public class StaticMethodChecker
extends Object

    The StaticMethodChecker invokes a static method of a student submitted class and compares the return value with the return value of a sample implementation of that method. Currently the static method may have zero to three arguments and a return value. The type of arguments and return value can be any of the following types: int, double, int[], double[], int[][] or double[][] or the respective wrapper classes. If the return values differ, a CommentAssertionError will be thrown that contains a detailed description of the causing method call.

    Example:

     @RunWith(GrajaRunner.class)
 public class Grader  {
    @InjectContext public static GraderContext ctx;
     private static StaticMethodChecker check;
     
    @BeforeClass public static void setUpOnce() {
         check= new StaticMethodChecker()
                 .callStaticMethod("create")
                 .withReturnType(double[].class)
                 .onSubmission(ctx.getPublicClassForName("ArrayFactory"))
                 .compareWithSample(Grader::sampleImpl)
                 .allowingMaxRuntimeMillis(10000)
                 .allowingDoubleReturnTolerance(0.0);
     }
    @Test public void testValid() {
         check.with("Valid parameters", 4, 0.6);
     }
    @Test public void testInvalid() {
         check.with("Invalid parameters", -1, 0.6);
     }
     private static double[] sampleImpl(int n, double v) {
         if (n < 0) throw new IllegalArgumentException();
         double[] a= new double[n];
         Arrays.fill(a, v);
         return a;
     }
 }

    When applied to the following poor student submission, the test leads to the following student feedback:

    Poor submission:

     public class ArrayFactory {
     public static double[] create(int n, double v) {
         return new double[n];
     }
 }

    Feedback of testValid method

    When trying to call

    ArrayFactory.create(4, 0.6)

    the following error was detected:

    Expected result: [0.6, 0.6, 0.6, 0.6]

    Observed result: [0.0, 0.0, 0.0, 0.0]

    Feedback of testInvalid method:

    When trying to call

    ArrayFactory.create(-1, 0.6)

    the following error was detected:

    Expected result: java.lang.IllegalArgumentException

    Observed result: java.lang.NegativeArraySizeException