HelloControllerTest.java

package hello;

import static org.hamcrest.Matchers.containsString;
import static org.mockito.Mockito.when;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

import io.micrometer.tracing.Span;
import io.micrometer.tracing.TraceContext;
import io.micrometer.tracing.Tracer;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc;
import org.springframework.test.context.bean.override.mockito.MockitoBean;
import org.springframework.test.web.servlet.MockMvc;

@SpringBootTest
@AutoConfigureMockMvc
class HelloControllerTest {

    @Autowired
    private MockMvc mvc;

    @MockitoBean
    private Tracer tracer;

    @Test
    void returnsTraceAndSpanDetailsAndParentFromTraceparent() throws Exception {
        Span span = org.mockito.Mockito.mock(Span.class);
        TraceContext traceContext = org.mockito.Mockito.mock(TraceContext.class);

        when(tracer.currentSpan()).thenReturn(span);
        when(span.context()).thenReturn(traceContext);
        when(traceContext.traceId()).thenReturn("4bf92f3577b34da6a3ce929d0e0e4736");
        when(traceContext.spanId()).thenReturn("00f067aa0ba902b7");
        when(traceContext.sampled()).thenReturn(Boolean.TRUE);

        mvc.perform(get("/")
                .header("traceparent", "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01"))
            .andExpect(status().isOk())
            .andExpect(content().string(containsString("current span: [Trace:")))
            .andExpect(content().string(containsString("Span:")))
            .andExpect(content().string(containsString("parents: [00f067aa0ba902b7]")));
    }
}