Add setup method to DataHandleTest

This allows subclasses to modify testing parameters,
first usecase is checkLength, which fails for
compressed handles, as the handdle can have a different length than
the content.

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

@@ -58,6 +58,13 @@ public abstract class DataHandleTest {
 			9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 0, -128, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, //
 			125, 127, -127, -125, -3, -2, -1 };
 
+	/**
+	 * If the handle's length is checked during {@link #checkReads(DataHandle)},
+	 * can be changed by subclasses (e.g. when processing compressed handles with
+	 * unknown length);
+	 */
+	protected boolean checkLength = true;
+
 	// -- Test methods --
 
 	@Test
@@ -72,11 +79,16 @@ public void testDataHandle() throws IOException {
 		{
 			assertEquals(getExpectedHandleType(), handle.getClass());
 
+			setup();
 			checkReads(handle);
 			checkWrites(handle);
 		}
 	}
 
+	protected void setup() {
+		// Subclasses can perform optional setup tasks here
+	}
+
 	// -- DataHandleTest methods --
 
 	public abstract Class<? extends DataHandle<?>> getExpectedHandleType();
@@ -94,7 +106,7 @@ protected <L extends Location> void checkReads(final DataHandle<L> handle)
 		throws IOException
 	{
 		assertEquals(0, handle.offset());
-		assertEquals(BYTES.length, handle.length());
+		if (checkLength) assertEquals(BYTES.length, handle.length());
 		assertEquals("UTF-8", handle.getEncoding());
 		assertEquals(ByteOrder.BIG_ENDIAN, handle.getOrder());
 		assertEquals(false, handle.isLittleEndian());