ChristmasBranch { public String toString() { return this.branch; } ChristmasBranch(int nbOfStars); String toString();  }
@Test public void firstBranchShouldHave1Star() { ChristmasBranch branch = new ChristmasBranch(1); assertThat(branch.toString()).isEqualTo("*"); }
@Test public void secondBranchShouldHave2StarAnd1Space() { ChristmasBranch branch = new ChristmasBranch(2); assertThat(branch.toString()).isEqualTo("* *"); }
@Test public void thirdBranchShouldHave3StarAnd2Space() { ChristmasBranch branch = new ChristmasBranch(3); assertThat(branch.toString()).isEqualTo("* * *"); }