Thanks! Yeah, I know the encoding should be supported that's why I had that exception anyway, but it's better to make it runtime. 👍 Coverage check won't let me merge it without the corresponding tests. A simple "shouldThrowWhenQueryEncodingNotSupported" test on each class would suffice. You'll need to add a @VisibileForTesting package private method in the QueryFilter class to urlEncode(String value), which will return the output of URLEncoder.encode(value, "UTF-8"); but for a single test on each class we will mock that to throw an exception when called with that value and encoding. Tests will look like this:

@Rule
public ExpectedException exception = ExpectedException.none()

@Test
public void shouldThrow...() throws Exception {
  exception.expect(IllegalStateException)
  exception.expectMessage("the exception message goes here")
  String value = "my=test value"
  QueryFilter filter = Mockito.spy(new QueryFilter())
  Mockito.doThrow(UnsupportedEncodingException).when(filter.urlEncode(value, "UTF-8"))
  filter.withQuery(value)
}

I'm sure you'll find similar tests for other classes. Please repeat that for each class and the coverage will raise again.
Cheers

Done. Couldn't find @VisibileForTesting somewhere in the project, so I've omitted it.