Provide unique IDs for all node info objects

spock-core/src/main/java/org/spockframework/runtime/SpecInfoBuilder.java

@@ -76,6 +76,7 @@ private void buildSpec() {
     SpecUtil.checkIsSpec(clazz);
 
     SpecMetadata metadata = clazz.getAnnotation(SpecMetadata.class);
+    spec.setUniqueId(clazz.getName());
     spec.setParent(null);
     spec.setPackage(ReflectionUtil.getPackageName(clazz));
     spec.setName(clazz.getSimpleName());
@@ -115,6 +116,7 @@ private void buildFeatures() {
 
   private FeatureInfo createFeature(Method method, FeatureMetadata featureMetadata) {
     FeatureInfo feature = new FeatureInfo();
+    feature.setUniqueId(String.format("%s.%s", spec.getUniqueId(), method.getName()));
     feature.setParent(spec);
     feature.setName(featureMetadata.name());
     feature.setLine(featureMetadata.line());

spock-core/src/main/java/org/spockframework/runtime/model/IterationInfo.java

@@ -31,6 +31,7 @@ public class IterationInfo extends NodeInfo<FeatureInfo, AnnotatedElement> imple
   private String displayName;
 
   public IterationInfo(FeatureInfo feature, int iterationIndex, Object[] dataValues, int estimatedNumIterations) {
+    setUniqueId(String.format("%s[%d]", feature.getUniqueId(), iterationIndex));
     setParent(feature);
     this.iterationIndex = iterationIndex;
     this.dataValues = dataValues;

spock-core/src/main/java/org/spockframework/runtime/model/NodeInfo.java

@@ -20,19 +20,37 @@
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.AnnotatedElement;
+import java.util.UUID;
 
 /**
  * Base class for runtime information about an element in a Spock specification.
  *
  * @author Peter Niederwieser
  */
 public abstract class NodeInfo<P extends NodeInfo, R extends AnnotatedElement> {
+  private String uniqueId = UUID.randomUUID().toString();
   private String name;
   private int line = -1;
   private P parent;
   private R reflection;
   private Object metadata;
 
+  /**
+   * A unique ID for this node during the current execution. Although some subclasses might
+   * provide semantic IDs, and the default implementation uses UUIDs, no semantic or format
+   * or maximum length is guaranteed. The only thing that should be assumed is, that the ID
+   * is unique across all nodes during the same invocation.
+   *
+   * @return the unique ID for this node
+   */
+  public String getUniqueId() {
+    return uniqueId;
+  }
+
+  public void setUniqueId(String uniqueId) {
+    this.uniqueId = uniqueId;
+  }
+
   public String getName() {
     return name;
   }