public static Matcher<String> text(String text) {
   return new MultiLineStringMatcher(text, System.getProperty("line.separator"));
 }
 @Test
 public void joinで文字列が連結される() throws Exception {
   String ls = System.getProperty("line.separator");
   String expected = "Hello" + ls + "World" + ls;
   assertThat(MultiLineString.join("Hello", "World"), is(text(expected)));
 }