SpringBoot Micrometer Tracer not available in integration tests

This application

@SpringBootApplication
public class TracertestApplication {

    public static void main(String[] args) {
        SpringApplication.run(TracertestApplication.class, args);
    }

    @Bean
    CommandLineRunner clr(Tracer tracer) {
        return (args) -> System.out.println(tracer);
    }
}

with this test

@SpringBootTest
class TracertestApplicationTests {

    @Test
    void contextLoads() {
    }

}

fails:

Parameter 0 of method clr in com.example.tracertest.TracertestApplication required a bean of type 'io.micrometer.tracing.Tracer' that could not be found.

We disable tracing in tests, which means there is no Tracer bean available. We disable metrics too, but we provide a SimpleMeterRegistry for the MeterRegistry.

Marcin has added a NOOP tracer which we should use as a Tracer in tests when tracing is not enabled. With this change, the test works again.

Comment From: mhalbritter

Here are the changes needed: https://github.com/mhalbritter/spring-boot/commit/c0fe55e186ac3a02c4c6d244d5bd6d9e02b3953c (needs Micrometer Tracing Snapshots)