@Test
public void testSetExpression() throws Exception {

	SdtElement element = createPlainTextContentControl(SdtBlock.class);
	PlainTextContent plainTextContent = new PlainTextContent(element);
	plainTextContent.setExpression("expression");
	String xmlString = XmlUtils.marshaltoString(
			plainTextContent.getXmlElement(), true);
	assertTrue(xmlString.contains("<w:tag w:val=\"expression\"/>"));
}