@Test void servesOtherContentFromClasspath() throws Exception {
    assertThat(get("/zipkin/test.txt").body().string())
      .isEqualToIgnoringWhitespace(stringFromClasspath(getClass(), "zipkin-lens/test.txt"));
  }
index.html is served separately. This tests other content is also loaded from the classpath.
zipkin-server/src/test/java/zipkin2/server/internal/ui/ITZipkinUiConfiguration.java