Ignore NullObservation in ObservationValidator

micrometer-observation-test/src/main/java/io/micrometer/observation/tck/ObservationValidator.java

@@ -16,6 +16,7 @@
 package io.micrometer.observation.tck;
 
 import io.micrometer.common.lang.Nullable;
+import io.micrometer.observation.NullObservation.NullContext;
 import io.micrometer.observation.Observation.Context;
 import io.micrometer.observation.Observation.Event;
 import io.micrometer.observation.ObservationHandler;
@@ -47,7 +48,7 @@ class ObservationValidator implements ObservationHandler<Context> {
     }
 
     ObservationValidator(Consumer<ValidationResult> consumer) {
-        this(consumer, context -> true);
+        this(consumer, context -> !(context instanceof NullContext));
     }
 
     ObservationValidator(Consumer<ValidationResult> consumer, Predicate<Context> supportsContextPredicate) {

micrometer-observation-test/src/test/java/io/micrometer/observation/tck/ObservationValidatorTests.java

@@ -15,6 +15,7 @@
  */
 package io.micrometer.observation.tck;
 
+import io.micrometer.observation.NullObservation;
 import io.micrometer.observation.Observation;
 import io.micrometer.observation.Observation.Event;
 import io.micrometer.observation.Observation.Scope;
@@ -253,4 +254,9 @@ void startErrorErrorStopShouldBeValid() {
         Observation.start("test", registry).error(new RuntimeException()).error(new RuntimeException()).stop();
     }
 
+    @Test
+    void nullObservationShouldBeIgnored() {
+        new NullObservation(registry).openScope();
+    }
+
 }

micrometer-observation/src/main/java/io/micrometer/observation/NullObservation.java

@@ -28,7 +28,7 @@
 public class NullObservation extends SimpleObservation {
 
     public NullObservation(ObservationRegistry registry) {
-        super("null", registry, new Context());
+        super("null", registry, new NullContext());
     }
 
     @Override
@@ -66,4 +66,16 @@ public Observation start() {
         return this;
     }
 
+    /**
+     * A special {@link Observation.Context} that should be used only in
+     * {@link NullObservation} in special cases where clearing of scopes is important. Its
+     * only purpose is to make scenarios through {@link NullObservation} distinguishable
+     * from "normal" {@link Observation Observations}.
+     *
+     * @since 1.14.0
+     */
+    public static class NullContext extends Context {
+
+    }
+
 }