@Test
	public void testMemoryBlockSplit() throws Exception {
		// split a memory block; verify that the byte viewer shows
		// the separator between blocks after the block is split
		env.showTool();
		Address addr = getAddr(0x01002000);

		MemoryBlock block = memory.getBlock(addr);
		Address newaddr = getAddr(0x01002009);

		txSwing(() -> {
			memory.split(block, newaddr);
		});

		ByteViewerComponent c = panel.getCurrentComponent();
		FieldLocation loc = getFieldLocation(newaddr);
		for (int i = 0; i < c.getNumberOfFields(); i++) {
			ByteField field = c.getField(loc.getIndex().subtract(BigInteger.ONE), i);
			assertEquals("..", field.getText());
		}
	}
Test editing in the Byte Viewer.
Ghidra/Features/ByteViewer/src/test.slow/java/ghidra/app/plugin/core/byteviewer/ByteViewerPlugin2Test.java