DataHandleTest: make checkLength in testReading optional

Some handles don't know their length, so we need an option to skip the
the length check.

src/test/java/org/scijava/io/handle/DataHandleTest.java

@@ -113,7 +113,7 @@ public void testEndianesSettings() throws IOException {
 	@Test
 	public void testReading() throws IOException {
 		try (final DataHandle<? extends Location> handle = createHandle()) {
-			checkBasicReadMethods(handle);
+			checkBasicReadMethods(handle, true);
 			checkEndiannessReading(handle);
 		}
 	}
@@ -168,13 +168,16 @@ public void populateData(final OutputStream out) throws IOException {
 	 * Checks basic byte reading methods.
 	 *
 	 * @param handle the handle to test
+	 * @param checkLength whether to check the total length of the handle
 	 * @throws IOException
 	 */
 	public <L extends Location> void checkBasicReadMethods(
-		final DataHandle<L> handle) throws IOException
+		final DataHandle<L> handle, boolean checkLength) throws IOException
 	{
 		assertEquals(0, handle.offset());
-		assertEquals(BYTES.length, handle.length());
+		if (checkLength) {
+			assertEquals(BYTES.length, handle.length());
+		}
 		assertEquals("UTF-8", handle.getEncoding());
 
 		// test read()

src/test/java/org/scijava/io/handle/ReadBufferDataHandleTest.java

@@ -64,7 +64,7 @@ public void testSmallBuffer() throws IOException {
 					new ReadBufferDataHandle(handle, 5))
 		{
 			// check with small buffersize
-			checkBasicReadMethods(bufferedHandle);
+			checkBasicReadMethods(bufferedHandle, true);
 			checkEndiannessReading(bufferedHandle);
 		}
 	}
@@ -127,7 +127,6 @@ public void testLargeRead() throws Exception {
 	}
 
 	@Test
-	@Ignore
 	@Override
 	public void testWriting() throws IOException {
 		// nothing to do here

src/test/java/org/scijava/io/handle/WriteBufferDataHandleTest.java

@@ -64,14 +64,12 @@ public DataHandle<? extends Location> createHandle() {
 	}
 
 	@Test
-	@Ignore
 	@Override
 	public void testReading() throws IOException {
 		// nothing to do
 	}
 
 	@Test
-	@Ignore
 	@Override
 	public void checkSkip() throws IOException {
 		// nothing to do