public Optional<Branch> findDefaultBranch() {
    return branches.stream().filter(Branch::isDefault).findFirst();
  }
@Test
  public void findDefaultBranch_givenNoBranches_returnEmptyOptional(){
    BranchesList branchesList = new BranchesList();

    Optional<Branch> defaultBranch = branchesList.findDefaultBranch();

    assertThat(defaultBranch).isNotPresent();
  }