@Test
  public void appendMappedQueryParamsWithExistingParams() {
    assertEquals(
        "http://test.com/1?a=b&c=d",
        HttpRequest.append("http://test.com/1?a=b",
            Collections.singletonMap("c", "d")));
    assertEquals(
        "http://test.com/1?a=b&c=d",
        HttpRequest.append("http://test.com/1?a=b&",
            Collections.singletonMap("c", "d")));

  }
Append with base URL already containing a '?'
lib/src/test/java/com/github/kevinsawicki/http/HttpRequestTest.java