### Question:
QuerystringBuilder { public String build() { return getParams().entrySet() .stream() .map(param -> param.getKey() + "=" + encode(param.getValue())) .collect(Collectors.joining("&")); }  QuerystringBuilder addParameter(String name, String value); String build();  }### Answer:
@Test public void shouldBeEmptyString_whenEmptyParameter() { QuerystringBuilder input = new QuerystringBuilder(); String output = input.build(); String expected = ""; assertThat(output).isEqualTo(expected); }