@Test
	public void concatenationTest() {
		Context c = new Context();
		DataFactory factory = new DataFactory();
		IVPString a = factory.createIVPString();
		IVPString b = factory.createIVPString();
		Concatenation conc = factory.createConcatenation();
		conc.setExpressionA(a.getUniqueID());
		conc.setExpressionB(b.getUniqueID());

		c.addString(a.getUniqueID(), "Hello, ");
		c.addString(b.getUniqueID(), "world!");

		HashMap map = new HashMap();
		map.put(a.getUniqueID(), a);
		map.put(b.getUniqueID(), b);
		map.put(conc.getUniqueID(), conc);

		IVPString result = (IVPString) conc.evaluate(c, map, factory);
		assertTrue(c.getString(result.getUniqueID()).equals("Hello, world!"));
	}