@Test void providesCollectorComponent_whenUrlSet() {
    TestPropertyValues.of("zipkin.collector.activemq.url:tcp://localhost:61611") // wrong port
      .applyTo(context);
    context.register(
      PropertyPlaceholderAutoConfiguration.class,
      ZipkinActiveMQCollectorConfiguration.class,
      InMemoryConfiguration.class);

    assertThatThrownBy(context::refresh)
      .isInstanceOf(BeanCreationException.class)
      .hasMessageContaining("Unable to establish connection to ActiveMQ broker");
  }
This prevents an empty ACTIVEMQ_URL variable from being mistaken as a real one
zipkin-server/src/test/java/zipkin2/server/internal/activemq/ZipkinActiveMQCollectorPropertiesTest.java