testlib: Add ConcurrentMapSpliteratorTester for spliterator characteristics

guava-testlib/src/com/google/common/collect/testing/ConcurrentMapTestSuiteBuilder.java

@@ -22,6 +22,7 @@
 import com.google.common.collect.testing.testers.ConcurrentMapRemoveTester;
 import com.google.common.collect.testing.testers.ConcurrentMapReplaceEntryTester;
 import com.google.common.collect.testing.testers.ConcurrentMapReplaceTester;
+import com.google.common.collect.testing.testers.ConcurrentMapSpliteratorTester;
 import java.util.List;
 
 /**
@@ -44,7 +45,8 @@ public static <K, V> ConcurrentMapTestSuiteBuilder<K, V> using(TestMapGenerator<
           ConcurrentMapPutIfAbsentTester.class,
           ConcurrentMapRemoveTester.class,
           ConcurrentMapReplaceTester.class,
-          ConcurrentMapReplaceEntryTester.class);
+          ConcurrentMapReplaceEntryTester.class,
+          ConcurrentMapSpliteratorTester.class);
 
   @SuppressWarnings("rawtypes") // class literals
   @Override

guava-testlib/src/com/google/common/collect/testing/testers/CollectionSpliteratorTester.java

@@ -75,6 +75,56 @@ public void testSpliteratorNotImmutable_collectionAllowsRemove() {
     assertFalse(collection.spliterator().hasCharacteristics(Spliterator.IMMUTABLE));
   }
 
+  /**
+   * Tests that the spliterator does not report both {@code CONCURRENT} and {@code SIZED}
+   * characteristics, which are incompatible per the {@link Spliterator} specification.
+   */
+  public void testSpliteratorNotConcurrentAndSized() {
+    Spliterator<E> spliterator = collection.spliterator();
+    assertFalse(
+        "spliterator should not have both CONCURRENT and SIZED characteristics",
+        spliterator.hasCharacteristics(Spliterator.CONCURRENT)
+            && spliterator.hasCharacteristics(Spliterator.SIZED));
+  }
+
+  /**
+   * Tests that the spliterator does not report both {@code CONCURRENT} and {@code IMMUTABLE}
+   * characteristics, which are incompatible per the {@link Spliterator} specification.
+   */
+  public void testSpliteratorNotConcurrentAndImmutable() {
+    Spliterator<E> spliterator = collection.spliterator();
+    assertFalse(
+        "spliterator should not have both CONCURRENT and IMMUTABLE characteristics",
+        spliterator.hasCharacteristics(Spliterator.CONCURRENT)
+            && spliterator.hasCharacteristics(Spliterator.IMMUTABLE));
+  }
+
+  /**
+   * Tests that if the spliterator reports {@code SORTED}, it also reports {@code ORDERED}, as
+   * required by the {@link Spliterator} specification.
+   */
+  public void testSpliteratorSortedRequiresOrdered() {
+    Spliterator<E> spliterator = collection.spliterator();
+    if (spliterator.hasCharacteristics(Spliterator.SORTED)) {
+      assertTrue(
+          "spliterator reporting SORTED must also report ORDERED",
+          spliterator.hasCharacteristics(Spliterator.ORDERED));
+    }
+  }
+
+  /**
+   * Tests that if the spliterator reports {@code SUBSIZED}, it also reports {@code SIZED}, as
+   * required by the {@link Spliterator} specification.
+   */
+  public void testSpliteratorSubsizedRequiresSized() {
+    Spliterator<E> spliterator = collection.spliterator();
+    if (spliterator.hasCharacteristics(Spliterator.SUBSIZED)) {
+      assertTrue(
+          "spliterator reporting SUBSIZED must also report SIZED",
+          spliterator.hasCharacteristics(Spliterator.SIZED));
+    }
+  }
+
   @J2ktIncompatible
   @GwtIncompatible // reflection
   public static Method getSpliteratorNotImmutableCollectionAllowsAddMethod() {

guava-testlib/src/com/google/common/collect/testing/testers/ConcurrentMapSpliteratorTester.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2025 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.collect.testing.testers;
+
+import com.google.common.annotations.GwtCompatible;
+import com.google.common.collect.testing.AbstractMapTester;
+import java.util.Spliterator;
+import java.util.concurrent.ConcurrentMap;
+import org.jspecify.annotations.NullMarked;
+import org.junit.Ignore;
+
+/**
+ * A generic JUnit test which tests spliterator characteristics on concurrent map views. Verifies
+ * that {@link ConcurrentMap} implementations return spliterators with the {@link
+ * Spliterator#CONCURRENT} characteristic on their {@code entrySet()}, {@code keySet()}, and {@code
+ * values()} views.
+ *
+ * <p>Can't be invoked directly; please see {@link
+ * com.google.common.collect.testing.ConcurrentMapTestSuiteBuilder}.
+ *
+ * @author Guava Authors
+ */
+@GwtCompatible
+@Ignore("test runners must not instantiate and run this directly, only via suites we build")
+// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
+@SuppressWarnings("JUnit4ClassUsedInJUnit3")
+@NullMarked
+public class ConcurrentMapSpliteratorTester<K, V> extends AbstractMapTester<K, V> {
+  @Override
+  protected ConcurrentMap<K, V> getMap() {
+    return (ConcurrentMap<K, V>) super.getMap();
+  }
+
+  /**
+   * Tests that the spliterator returned by {@code entrySet().spliterator()} has the {@code
+   * CONCURRENT} characteristic.
+   */
+  public void testEntrySetSpliteratorHasConcurrent() {
+    Spliterator<?> spliterator = getMap().entrySet().spliterator();
+    assertTrue(
+        "entrySet().spliterator() should have CONCURRENT characteristic",
+        spliterator.hasCharacteristics(Spliterator.CONCURRENT));
+  }
+
+  /**
+   * Tests that the spliterator returned by {@code keySet().spliterator()} has the {@code
+   * CONCURRENT} characteristic.
+   */
+  public void testKeySetSpliteratorHasConcurrent() {
+    Spliterator<?> spliterator = getMap().keySet().spliterator();
+    assertTrue(
+        "keySet().spliterator() should have CONCURRENT characteristic",
+        spliterator.hasCharacteristics(Spliterator.CONCURRENT));
+  }
+
+  /**
+   * Tests that the spliterator returned by {@code values().spliterator()} has the {@code
+   * CONCURRENT} characteristic.
+   */
+  public void testValuesSpliteratorHasConcurrent() {
+    Spliterator<?> spliterator = getMap().values().spliterator();
+    assertTrue(
+        "values().spliterator() should have CONCURRENT characteristic",
+        spliterator.hasCharacteristics(Spliterator.CONCURRENT));
+  }
+}