UISpec4J: Java GUI Testing Made Simple Blog


    UISpec4J is an open source functional and/or unit-testing Java library for Swing-based Java applications that is focused on simplicity. UISpec4J's APIs are designed to hide, as much as possible, the complexity of Swing, resulting in easy-to-write and easy-to-read test scripts.

    GUI Testing

    With the advent of Agile development processes such as Extreme Programming (XP), automated testing is being adopted by an increasingly larger number of development teams. There is, however, one area of software that has always had a reputation for being difficult to test: graphical user interfaces.

    In this article, we explain how we faced the same problem on an XP project and came up with a solution by building our own GUI testing toolkit, which is now available as a free open source product. But before delving into this, let's start from the beginning: how can we test GUIs?

    Using Event-Driven Robots

    When it comes to setting up automated tests for graphical user interfaces, the conventional approach is to use event-driven robots that record human interactions with the interface and can replay these interactions at will. The interesting part of this approach is that it is very simple to create new tests--you don't need a developer or someone with scripting skills to do this.

    The trouble is, this simplicity comes with a number of down sides:

    • You need to have the interface to record the tests. You thus cannot use the tests as a guide for driving the development, and you make your development cycles longer by preventing developers and testers from working at the same time on a given feature.

    • The test suite becomes a burden, preventing changes in the GUI. Writing the first twenty tests is easy, but what do you do when you have more than a thousand tests? When you want to change a given screen in your application, will you be willing to chase down the hundreds of impacted tests and record them all again?

    In other words, using generated scripts is simply not always compatible with an incremental, agile approach.

    Using Test-Specific APIs

    A better solution would be to manually code these tests, so that they can be written before the interface is available, and use a rich programming language allowing the incremental refactoring of a test suite that will remain easy to modify. In the Java/Swing world, there are several existing libraries for doing this, such asAbbot, JFCUnit, Marathon, and Jemmy.

    When we were working on a large Java/Swing application several years ago, we had a look at these libraries, but in the end we didn't use them because their APIs were too close to Swing and resulted in tests that looked too "technical."

    The UISpec4J Approach

    We wanted a library that would nicely fit into our XP process:

    • Test-first programming: For both panel-level unit testing and application-level acceptance testing, meaning that we would be able to write tests reading like user interactionsbefore the GUI was available.

    • Refactoring: We would use the Java language (rather than, say, Python or Ruby) to benefit from the powerful refactoring tools available for that language, thus limiting duplication in the test suites.

    We then resolved to create our own testing library--and UISpec4J was born.

    Let's now have a look at some UISpec4J code, to see whether these goals have been successfully met.

    The Address Book Sample Application

    We obviously can't claim to have the most original sample application on the planet, but be that as it may, the application we will be using here is a simple address book that manages a collection of contacts sorted by categories. Figure 1 shows the GUI of this application.

    The address book GUI is split into three main areas of interest:

    1. On the left-hand side, a table displays a list of contacts with basic details. The user can add a new entry in the table by clicking on the button labeled ... "New contact." How intuitive!
    2. On the right-hand side, a tree shows available categories for filtering contacts. A "New category" button is placed on top of the tree for creating categories.
    3. At the bottom of the frame, a form details the currently selected contact. The form is composed of labels and editable text fields.

    AddressBook screenshot
    Figure 1. Address Book screen

    A list of possible interactions with the address book could be:

    • Creating a new contact.
    • Switching between contacts.
    • Editing an existing contact.
    • Filtering contacts by category.

    But before playing with the components, we need to set up a test class and catch our application.

    Creating a Test Class

    A typical way to create a UISpec4J test is to create a class extending UISpecTestCase, which is itself a subclass of JUnit'sTestCase.

    public class AddressBookTest extends UISpecTestCase { ... }

    We then tell this class that it needs to run the address book application using the main() found in theAddressBook class, and that it can run this application with no arguments. To do this, we set up an "adapter" (UISpecAdapter), whose role is to implement the adaptation between the tests suite and the application. In most cases, we just use the MainClassAdapter provided with the library:

    public class AddressBookTest extends UISpecTestCase { protected void setUp() throws Exception { setAdapter(new MainClassAdapter(Main.class, new String[0])); } ... }

    We are now ready to create our first test.

    First Test: Creating a Contact

    Let's write a test that creates a new contact using the "New contact" button and then checks that a new row appears in the contacts table.

    The UISpecTestCase class proposes agetMainWindow() method that uses theUISpecAdapter introduced above to return an UISpec4JWindow object representing the window displayed by the application. This Window object can be used to fetch individual UI components such as the "New contact" button, the contacts table, and the various text fields used for entering contact information.

    Here is the corresponding test:

    public void testCreatingAContact() throws Exception { // 1. Retrieve the components Window window = getMainWindow(); Table table = window.getTable(); Button newContactButton = window.getButton("New contact"); // 2. Check that the contacts table is empty and displays // the proper column names assertTrue(table.getHeader().contentEquals(new String[]{ "First name", "Last name", "E-mail", "Phone", "Mobile" })); assertTrue(table.isEmpty()); // 3. Click on the "New contact" button and check that an // empty row is displayed in the contacts table newContactButton.click(); assertTrue(table.contentEquals(new String[][]{ {"", "", "", "", ""} })); assertTrue(table.rowIsSelected(0)); // 4. Change the fields of the created empty contact and check // that the contacts table is updated accordingly window.getTextBox("first").setText("Homer"); window.getTextBox("last").setText("Simpson"); window.getTextBox("email").setText("homer@simpson.com"); window.getTextBox("phone").setText(""); window.getTextBox("mobile").setText(""); assertTrue(table.contentEquals(new String[][]{ {"Home", "Simpson", "homer@simpson.com", "012345", "242424"} })); }

    Finding Components

    As you can see in the first part of the test, we use thewindow object to retrieve the components using specific methods such as getTree(),getButton(), etc. For each component type, there are various strategies for fetching individual components.

    If you know that there is only one button in the panel, then just ask for it!

    Button button = panel.getButton();

    If there are several buttons in the panel, you specify which button you want using its displayed label:

    Button button = panel.getButton("New contact");

    If there are several buttons with the same displayed label, you can distinguish among them using an "inner name" provided in the production code by the application developers with theJComponent.setName() method. This is, for instance, what we do for the text boxes displayed at the bottom of the address book window--they all look the same, so we need to rely on internal names that we set in the production code:first, last, email, etc. For instance:

    TextBox emailBox = panel.getTextBox("email");

    If none of these methods can do the job, you can still provide your own piece of code for matching components:

    Button button = panel.getButton(new ComponentMatcher(){ boolean matches(Component component) { return component.isEnabled(); } });

    Note: for I18N purposes, we usually force the default locale toLocale.EN in our tests and use English names for retrieving components.

    Using a Table Component

    The Table class provides lots of methods for checking and manipulating the underlying JTablecomponent. Most of these methods work with two-dimensional arrays representing what the end user is expected to see. For instance:

    assertTrue(table.contentEquals(new String[][]{ {"Homer", "Simpson", "homer@simpson.com", "012345", "2424242"}, {"Bart", "Simpson", "bart@simpson.com", "123456", "34343434"} }));

    Note: the Table.contentEquals() method, as many other UISpec4J component methods, return Assertionobjects instead of Booleans. These Assertion objects are used by UISpec4J to implement retry strategies, mostly for the case of multithreaded GUIs where there might be slight delays between actions performed in the tests and the corresponding changes in the UI. This mechanism is completely transparent in the tests, provided that you use UISpecTestCase'sassertXxx methods, or those of theUISpecAssert class.

    Second Test: Dealing with the Categories Tree

    Let's now move to a more complicated test: "a contact must belong to the category in which it was created." Additionally, selecting a category in the tree should trigger the filtering of the contact list.

    Here is the code for this test:

    public void testContactsBelongToTheirOriginatedCategories() throws Exception { // 1. Create the categories structure and check the display createCategory("", "friends"); createCategory("", "work"); createCategory("work", "design-up"); assertTrue(window.getTree().contentEquals("All\n" + " friends\n" + " work\n" + " design-up")); // 2. Create some entries in the "friends" category window.getTree().select("friends"); window.getButton("New contact").click(); window.getTextBox("first").setText("Homer"); window.getTextBox("last").setText("Simpson"); window.getButton("New contact").click(); window.getTextBox("first").setText("Marge"); window.getTextBox("last").setText("Simpson"); // 3. Create some entries in the "work/design-up" category window.getTree().select("work/design-up"); window.getButton("New contact").click(); window.getTextBox("first").setText("Regis"); window.getTextBox("last").setText("Medina"); window.getButton("New contact").click(); window.getTextBox("first").setText("Pascal"); window.getTextBox("last").setText("Pratmarty"); // 4. Check the contents of the root category (category "All") window.getTree().selectRoot(); assertTrue(window.getTable().contentEquals(new String[][]{ {"Homer", "Simpson", "", "", ""}, {"Marge", "Simpson", "", "", ""}, {"Regis", "Medina", "", "", ""}, {"Pascal", "Pratmarty", "", "", ""}, })); // 5. Check the contents of the "friends" category window.getTree().select("friends"); assertTrue(window.getTable().contentEquals(new String[][]{ {"Homer", "Simpson", "", "", ""}, {"Marge", "Simpson", "", "", ""}, })); // 6. Check the contents of the "work" category window.getTree().select("work"); assertTrue(window.getTable().contentEquals(new String[][]{ {"Regis", "Medina", "", "", ""}, {"Pascal", "Pratmarty", "", "", ""}, })); }

    Steps 1 to 3 set up the initial environment and steps 4 to 6 check the contacts displayed for each category. For the setup part, we use a createCategory() method that is described in the next section. On our own projects, we usually end up creating a lot of utility methods like this one, and extract a kind of functional language for manipulating the GUI.

    Working with Dialogs

    The code of the createCategory() method is shown below. We first click on the "New category" button, and then intercept a modal dialog that pops up for querying the name of the category to create.

    protected void createCategory(String parentCategoryPath, String categoryName) { window.getTree().select(parentCategoryPath); WindowInterceptor.init(window.getButton("New Category").triggerClick()) .process(new WindowHandler() { Trigger process(Window dialog) { assertTrue(dialog.titleEquals("Category name:")); dialog.getInputTextBox().setText(categoryName); return dialog.getButton("OK").triggerClick(); } }) .run(); } 

    This method uses the WindowInterceptor utility class to catch the popped-up modal dialog. This is the main class of UISpec4J's window interception mechanism, and provides a means for working with windows without requiring the user interface to be showing on the screen and without requiring any change in the production code.

    Here is how this works:

    1. init(): We first initialize the interceptor with what we call a "trigger." A Triggeris a piece of code that causes a dialog to be shown by the application--for instance, an Open button that displays a file chooser, or a Delete button that displays a confirmation window. Many UISpec4J components offer ready-to-use components throughtriggerXXX() methods, but you can also provide your own implementation of the Trigger interface.

    2. process(): The window displayed by the trigger is caught and given to a WindowHandlerinterface. We provide a WindowHandler implementation that first checks that the displayed window's title is "Category name", then enters the value of the categoryNamevariable into the displayed text field, and then closes the window using its OK button.

      Implementing interceptions like this can look cumbersome, and one would like to be able to test the displayed window without having to create inner classes. But in the case of modal dialogs there is no choice: the application is waiting for the dialog to be closed, which means that the main thread of the application is blocked, so you need to process the dialog within a new thread. One of the strengths of the interception mechanisms is that they hide the multithreading issues associated with the management of modal dialogs.

      Should you need to intercept non-modal dialogs, however, things are much simpler. You would retrieve the window from within the test with a single statement; for instance:

      Window window = WindowInterceptor.run(window.getButton("Show").triggerClick());
      window.getTable() ...
      window.getButton() ...
    3. run: This is when the whole interception gets really executed. The trigger is run, and the displayed window is processed by the handler. Therun() method will throw an exception if no window is shown or if the displayed modal dialog is never closed by the handler.

    It is important to note here that the UISpec4J toolkit is ultimately responsible for handling the display of every window: if the application tries to show a dialog box or a window from outside a WindowInterceptor call, the toolkit will immediately raise an exception and make the current test fail.

    Using Tree Components

    The tree content is being checked before filling the "friends" and "work/design-up" categories with some contacts. As for tables, we also use a "graphical" representation: an indented concatenation of the string representations of the tree nodes separated by the newline (\n) character. In our case:

    assertTrue(window.getTree().contentEquals( "All\n" + " friends\n" + " work\n" + " design-up"));

    You will also have noticed that tree paths are expressed with simple strings, usually the displayed tree node names separated with slashes--for instance, work/design-up. This policy can be overriden quite easily when using UISpec4J'sTree component.

    Other UISpec4J Features

    UISpec4J provides other interesting features that we will only present briefly here.

    Using Displayed Values Instead of Internal Ones

    UISpec4J uses the values displayed by the components. For complex components such as JList,JTable, or JTree, this means relying on renderers, not just the internal model of the component. For most cases, these renderers use JLabel components, so UISpec4J will simply retrieve these labels and check their displayed text. In more advanced cases, you can easily customize how String values are to be interpreted for a specific complex component.

    Extending UISpec4J to Handle New Kinds of Components

    Even though the UISpec4J API is rich enough to handle most of the situations we have had to deal with, there will always be new situations to take into account. For instance, many projects will want to use UISpec4J with custom-made UI components for which there is no UISpec4J wrapper--for instance, a Table with advanced sorting and filtering capabilities, or aCalendar component, or any custom component coming along with third-party libraries (e.g. JavaHelp).

    UISpec4J provides an extension mechanism that allows you to implement your own UISpec4J component wrappers, and plug them into the library by enhancing the Panel class so that it can be used to find them in containers as for any other UISpec4J component.


    This article presents only an overview of UISpe4J's philosophy and capabilities. This framework aims to ease the automated testing of Swing-based applications:

    • A large toolset allows for writing clear test scripts with little effort.
    • Advanced users can extend this toolset for manipulating third-party components and checking rendered content in more detail.

    Should you have any problems, questions, or suggestions, please feel free to either or join our forum--we look forward to hearing from you!