Fix a bug in shrinking logic

Author: leventov

src/main/java/io/timeandspace/smoothie/SmoothieMapStats.java

@@ -37,6 +37,10 @@ final class SmoothieMapStats {
     @Nullable OrdinarySegmentStats @Nullable [][] ordinarySegmentStatsPerOrderAndNumFullSlots =
             new OrdinarySegmentStats[MAX_SEGMENTS_ARRAY_ORDER + 1][];
 
+    int getNumAggregatedSegments() {
+        return numAggregatedSegments;
+    }
+
     int getNumInflatedSegments() {
         return numInflatedSegments;
     }

src/main/javaTemplates/io/timeandspace/smoothie/SmoothieMap.java

@@ -4507,6 +4507,7 @@ private void doShrinkInto(Segment<K, V> fromSegment, final long fromSegment_bitS
                                 ", intoSegment_allocCapacity: " + intoSegment_allocCapacity);
                     }
 
+                    this.modCount++;
                     byte tag = (byte) tagBits(hash);
                     writeEntry(intoSegment,
                             /* if Interleaved segments Supported intermediateSegments */

src/test/java/io/timeandspace/smoothie/ShrinkTest.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) The SmoothieMap 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 io.timeandspace.smoothie;
+
+import org.junit.Assert;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+
+public class ShrinkTest {
+    @Test
+    public void testShrink() {
+        final SmoothieMap<Integer, Integer> map = SmoothieMap
+                .<Integer, Integer>newBuilder().doShrink(true).build();
+
+        Random r = new Random(1);
+        List<Integer> keys = new ArrayList<>();
+        for (int i = 0; i < 10_000; i++) {
+            int key = r.nextInt();
+            keys.add(key);
+            map.put(key, key);
+        }
+
+        for (Integer key : keys) {
+            map.remove(key);
+        }
+        final SmoothieMapStats stats = new SmoothieMapStats();
+        map.aggregateStats(stats);
+        Assert.assertEquals(1, stats.getNumAggregatedSegments());
+    }
+}