Home > Point2 - Technical > Creating a Fitnesse Wiki Widget

Creating a Fitnesse Wiki Widget

April 2, 2009


We are using Fitnesse to acceptance test our REST apis.  One of our calls requires that a UUID be created and then used in several places throughout the test.  The syntax we wanted to use was :-

!define myUUID ${!uuid}

This however is not possible, because the !define widget in fitnesse does not support value interpolation.  So, we hit on a revised syntax which looks like this:-


This assigns a randomly generated UUID to the variable myUUID, which is then referencable by the usual fitnesse wiki syntax ${myUUID}.  The implementation looks like this:-

import java.util.UUID;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

import fitnesse.wikitext.widgets.ParentWidget;
import fitnesse.html.HtmlUtil;

public class GuidWidget extends ParentWidget {

public static final String REGEXP = “!uuid\\{[\\w]+\\}”;
private static final Pattern pattern = Pattern.compile(“!uuid\\{([\\w]+)\\}”);

private String varName;

public GuidWidget(ParentWidget parent, String text) throws Exception {
final Matcher matcher = pattern.matcher(text);
varName = matcher.group(1);

public String render() throws Exception {
this.parent.addVariable(varName, UUID.randomUUID().toString());
return HtmlUtil.metaText(varName + ” assigned a UUID”);

public String asWikiText() throws Exception {
return “!uuid{” + varName + “}”;

When researching how to implement my own custom widget, I read several posts complaining that !define myVar {!MyWidget(thing)} does not evaluate the custom widget in the define widget.  Well, the ParentWidget class, which you have to extend, allows you to call parent.addVariable(varName, varValue) which does the magic for you.
The one slightly tricky part was that you need to register your widget in the plugins.properties file, and then make sure the new class is in the classpath of fitnesse (not your tests via the !path property).  To do that, all you need to do is add the compiled class to a jar, put the jar in your fitnesse runner lib directory, then amend the run.bat or run.sh.  Our new run.bat looks like this:-

java -cp fitnesse.jar;lib\guid.jar fitnesse.FitNesse ....

When fitnesse starts, it reads all the widgets in the plugins.properties WikiWidgets property and loads them.  It then outputs a list of the widgets that it has added to the console out.

By: Chris Tarttelin

%d bloggers like this: