Add assertion support for Span hasException(null) (#8033)

Author: trask

sdk/testing/src/main/java/io/opentelemetry/sdk/testing/assertj/SpanDataAssert.java

@@ -375,19 +375,28 @@ public SpanDataAssert hasAttributesSatisfyingExactly(Iterable<AttributeAssertion
 
   /**
    * Asserts the span has an exception event for the given {@link Throwable}. The stack trace is not
-   * matched against.
+   * matched against. If {@code exception} is {@code null}, asserts the span has no exception event.
    */
   // Workaround "passing @Nullable parameter 'stackTrace' where @NonNull is required", Nullaway
   // seems to think assertThat is supposed to be passed NonNull even though we know that can't be
   // true for assertions.
   @SuppressWarnings("NullAway")
-  public SpanDataAssert hasException(Throwable exception) {
+  public SpanDataAssert hasException(@Nullable Throwable exception) {
     EventData exceptionEvent =
         actual.getEvents().stream()
             .filter(event -> event.getName().equals(EXCEPTION_EVENT_NAME))
             .findFirst()
             .orElse(null);
 
+    if (exception == null) {
+      if (exceptionEvent != null) {
+        failWithMessage(
+            "Expected span [%s] to have no exception event but had <%s>",
+            actual.getName(), exceptionEvent);
+      }
+      return this;
+    }
+
     if (exceptionEvent == null) {
       failWithMessage(
           "Expected span [%s] to have an exception event but only had events <%s>",

sdk/testing/src/test/java/io/opentelemetry/sdk/testing/assertj/TraceAssertionsTest.java

@@ -301,6 +301,8 @@ void passing() {
 
     assertThat(RESOURCE.getAttributes())
         .containsOnly(entry(DOG, "bark"), entry(AttributeKey.booleanKey("dog is cute"), true));
+
+    assertThat(buildTestSpan(SPAN_ID1, "span")).hasException(null);
   }
 
   @Test
@@ -564,6 +566,8 @@ void failure() {
     assertThatThrownBy(
             () -> assertThat(SPAN1).hasException(new IllegalArgumentException("good argument")))
         .isInstanceOf(AssertionError.class);
+    assertThatThrownBy(() -> assertThat(SPAN1).hasException(null))
+        .isInstanceOf(AssertionError.class);
     assertThatThrownBy(() -> assertThat(SPAN1).hasLinks()).isInstanceOf(AssertionError.class);
     assertThatThrownBy(() -> assertThat(SPAN1).hasLinks(Collections.emptyList()))
         .isInstanceOf(AssertionError.class);