Add tests

Author: garydgregory

src/test/java/org/apache/commons/io/input/ProxyInputStreamTest.java

@@ -327,6 +327,17 @@ void testReadEof() throws Exception {
         }
     }
 
+    @Test
+    void testSetReference() throws Exception {
+        final ByteArrayInputStream first = new ByteArrayInputStream(new byte[2]);
+        try (ProxyInputStream wrapped = new ProxyInputStreamFixture(first)) {
+            assertSame(first, wrapped.unwrap());
+            final NullInputStream in = new NullInputStream();
+            wrapped.setReference(in);
+            assertSame(in, wrapped.unwrap());
+        }
+    }
+
     @Test
     void testSubclassAfterReadConsumer() throws Exception {
         final byte[] hello = "Hello".getBytes(StandardCharsets.UTF_8);
@@ -355,4 +366,12 @@ void testSubclassAfterReadConsumer() throws Exception {
         // @formatter:on
     }
 
+    @Test
+    void testUnwrap() throws Exception {
+        final ByteArrayInputStream first = new ByteArrayInputStream(new byte[2]);
+        try (ProxyInputStream wrapped = new ProxyInputStreamFixture(first)) {
+            assertSame(first, wrapped.unwrap());
+        }
+    }
+
 }