@Test
  void customExpander() throws Exception {
    final MethodMetadata md = parseAndValidateMetadata(CustomExpander.class, "clock", Clock.class);

    assertThat(md.indexToExpanderClass()).containsExactly(entry(0, ClockToMillis.class));
  }
Body type is only for the body param.
core/src/test/java/feign/DefaultContractTest.java