Serialization test.

pom.xml

@@ -66,6 +66,8 @@
             <configuration>
                <source>1.5</source>
                <target>1.5</target>
+               <testSource>1.8</testSource>
+               <testTarget>1.8</testTarget>
             </configuration>
          </plugin>
          <plugin>

src/test/java/com/zaxxer/sparsebits/SerializationTest.java

@@ -0,0 +1,82 @@
+package com.zaxxer.sparsebits;
+
+import java.io.*;
+import java.nio.file.*;
+import java.util.*;
+import java.util.stream.*;
+
+import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests serialization of SparseBitSet of different number of set bits,
+ * from 1 to MAX_BITS.
+ */
+public class SerializationTest {
+
+  private static final Path DST = Paths.get(System.getProperty("java.io.tmpdir"), "sbs.ser");
+  private static final int MAX_BITS = Integer.parseInt(System.getProperty("test.max_bits", "100"));
+
+  private int numOfBits;
+  private int[] data;
+  private SparseBitSet sparseBitSet;
+
+  @Test
+  public void testFromOneToNBits() {
+    IntStream.range(1, MAX_BITS + 1).forEach(this::execute);
+  }
+
+  private void execute(int numOfBits) {
+    try {
+      this.numOfBits = numOfBits;
+      this.sparseBitSet = new SparseBitSet();
+
+      createData();
+      fillSparseBitSet();
+      write();
+
+      this.sparseBitSet = null;
+      sortData();
+      read();
+
+      verify();
+    } catch (Exception e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+  private void verify() {
+    for (int i = sparseBitSet.nextSetBit(0), j = 0; i >= 0; i = sparseBitSet.nextSetBit(i + 1), j++) {
+      assertEquals(data[j], i);
+    }
+  }
+
+  private void createData() {
+    Set<Integer> s = new HashSet<>();
+    Random r = new Random();
+    while (s.size() < numOfBits) {
+      s.add(r.nextInt(Integer.MAX_VALUE));
+    }
+    data = s.stream().mapToInt(i -> i).toArray();
+  }
+
+  private void sortData() {
+    Arrays.sort(data);
+  }
+
+  private void fillSparseBitSet() {
+    IntStream.of(data).forEach(sparseBitSet::set);
+  }
+
+  private void write() throws Exception {
+    try (ObjectOutputStream s = new ObjectOutputStream(new FileOutputStream(DST.toFile()))) {
+      s.writeObject(sparseBitSet);
+    }
+  }
+
+  private void read() throws Exception {
+    try (ObjectInputStream s = new ObjectInputStream(new FileInputStream(DST.toFile()))) {
+      sparseBitSet = (SparseBitSet) s.readObject();
+    }
+  }
+}