rewrite asserts without warnings

Author: m.zharinova

spring-boot-3-demo-app/src/test/java/io/github/mfvanek/spring/boot3/test/service/PublicApiServiceTest.java

@@ -11,6 +11,7 @@
 import io.github.mfvanek.spring.boot3.test.support.TestBase;
 import io.micrometer.observation.Observation;
 import io.micrometer.observation.ObservationRegistry;
+import io.micrometer.tracing.Span;
 import io.micrometer.tracing.Tracer;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -86,12 +87,15 @@ void retriesOnceToGetZonedTime(@Nonnull final CapturedOutput output) {
     }
 
     @Test
-    void throwsJsonProcessingExceptionWithBdResponse(CapturedOutput output) {
+    void throwsJsonProcessingExceptionWithBadResponse(CapturedOutput output) {
         final String zoneName = stubBadResponse();
         Observation.createNotStarted("test", observationRegistry).observe(() -> {
             final LocalDateTime result = publicApiService.getZonedTime();
+            final Span currentSpan = tracer.currentSpan();
+
+            assert currentSpan != null;
             assertThat(result).isNull();
-            assertThat(tracer.currentSpan().context().traceId()).isNotNull();
+            assertThat(currentSpan.context().traceId()).isNotNull();
             assertThat(output.getAll()).contains("Failed to convert response");
         });
         verify(1, getRequestedFor(urlPathMatching("/" + zoneName)));