@Test void parsesListOfLocalhosts_failsWhenAllInvalid() {
    InitialEndpointSupplier supplier = new InitialEndpointSupplier(HTTP, ",");
    assertThatThrownBy(supplier::get)
      .isInstanceOf(IllegalArgumentException.class)
      .hasMessage("No valid endpoints found in ES hosts: ,");
  }
This helps ensure old setups don't break (provided they have http port 9200 open)
zipkin-server/src/test/java/zipkin2/server/internal/elasticsearch/InitialEndpointSupplierTest.java