@Override
  protected void createParents() {
    parents = new ArrayList<IIndividual>();

    // Parent genotype
    ExprTree genotype = new ExprTree();
    genotype.addBlock(new Add());
    genotype.addBlock(new X());
    genotype.addBlock(new Sub());
    genotype.addBlock(new Mul());
    genotype.addBlock(new Y());
    genotype.addBlock(new Z());
    genotype.addBlock(new X());

    // Add individual to the parents set
    parents.add(new ExprTreeIndividual(genotype));
  }
  @Override
  protected void createExpected() {
    expected = new ArrayList<IIndividual>();

    // Mutated individual genotype
    ExprTree genotype = new ExprTree();
    genotype.addBlock(new Add());
    genotype.addBlock(new X());
    genotype.addBlock(new Add());
    genotype.addBlock(new Sub());
    genotype.addBlock(new X());
    genotype.addBlock(new Y());
    genotype.addBlock(new Z());

    // Add individual to expected set
    expected.add(new ExprTreeIndividual(genotype));
  }