init rxjava3 junit test

update testing logics for rxjava

update test instance level

migrate rxjava3 unit tests to java

sort traces for test - format code style

migrate rest of tests for rxjava3

format code style

Author: kaibocai7

instrumentation/reactor/reactor-3.1/testing/src/main/java/io/opentelemetry/instrumentation/reactor/AbstractReactorCoreTest.java

@@ -9,6 +9,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
+import com.google.common.primitives.Ints;
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.instrumentation.testing.junit.InstrumentationExtension;
 import io.opentelemetry.sdk.testing.assertj.TraceAssert;
@@ -115,6 +116,22 @@ void basicFlux() {
                 span -> span.hasName("add one").hasParent(trace.getSpan(0))));
   }
 
+  @Test
+  void basicFluxIterable() {
+    List<Integer> result =
+        testing.runWithSpan(
+            "parent",
+            () -> Flux.fromIterable(Ints.asList(5, 6)).map(this::addOne).collectList().block());
+    assertThat(result).containsExactly(6, 7);
+
+    testing.waitAndAssertTraces(
+        trace ->
+            trace.hasSpansSatisfyingExactly(
+                span -> span.hasName("parent").hasNoParent(),
+                span -> span.hasName("add one").hasParent(trace.getSpan(0)),
+                span -> span.hasName("add one").hasParent(trace.getSpan(0))));
+  }
+
   @Test
   void twoOperationsFlux() {
     List<Integer> result =