Add more test coverage for maximum buffer size

src/test/java/com/amazon/ion/impl/ResizingPipedInputStreamTest.java

@@ -25,6 +25,7 @@
 import static org.junit.runners.Parameterized.Parameter;
 import static org.junit.runners.Parameterized.Parameters;
 
+@SuppressWarnings("resource")
 @RunWith(Parameterized.class)
 public class ResizingPipedInputStreamTest {
 

src/test/java/com/amazon/ion/impl/UnifiedInputBufferXTest.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2007-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * or in the "license" file accompanying this file. This file 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.amazon.ion.impl;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class UnifiedInputBufferXTest {
+
+    @Test
+    public void ctorThrowsWithIllegalInitialPageSize() {
+        assertThrows(IllegalArgumentException.class,
+                () -> new UnifiedInputBufferX.Chars(-1));
+
+        assertThrows(IllegalArgumentException.class,
+                () -> new UnifiedInputBufferX.Chars(Integer.MAX_VALUE));
+    }
+
+    @Test
+    public void ctorWorksWithLegalInitialPageSize() {
+        new UnifiedInputBufferX.Chars(0);
+        new UnifiedInputBufferX.Chars(_Private_IonConstants.ARRAY_MAXIMUM_SIZE);
+    }
+
+}

src/test/java/com/amazon/ion/impl/UnifiedInputStreamXTest.java

@@ -15,14 +15,17 @@
 
 package com.amazon.ion.impl;
 
-import org.junit.Assert;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
 
-public class UnifiedInputStreamXTest extends Assert {
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class UnifiedInputStreamXTest {
+
     @Test
     public void testReadExactlyAvailable() throws Exception {
         class TestInputStream extends InputStream {