Write Tests That Use App Testing and Mocking Frameworks

This example shows how to write tests that use the app testing framework and the mocking framework. The app contains a file selection dialog box and a label indicating the selected file. To test the app programmatically, use a mock object to define the behavior of the file selector.

Create App

Create the launchApp app in your current folder. The app allows a user to select an input file and displays the name of the file in the app. The file selection dialog box is a blocking modal dialog box that waits for user input.

function app = launchApp
f = uifigure;
button = uibutton(f,"Text","Input file");
button.ButtonPushedFcn = @(src,event) pickFile;
label = uilabel(f,"Text","No file selected");
label.Position(1) = button.Position(1) + button.Position(3) + 25;
label.Position(3) = 200;

% Add components to app
app.UIFigure = f;
app.Button = button;
app.Label = label;

    function file = pickFile
        [file,~,status] = uigetfile("*.*");
        if status
            label.Text = file;
        end
    end
end

To explore the properties of the app prior to testing, call the launchApp function at the command prompt. This step is not necessary for the tests, but it is helpful to explore the properties used by the app tests. For example, use app.Button to access the Input file button within the app.

app = launchApp;
app.Button

ans = 

  Button (Input file) with properties:

               Text: 'Input file'
               Icon: ''
    ButtonPushedFcn: @(src,event)pickFile
           Position: [100 100 100 22]

  Show all properties

Test App with Manual Intervention

Create the LaunchAppTest test class without using mocks. The test requires that the file input.txt exists in your current folder. If it does not exist, create it. The test presses the Input file button programmatically and verifies that the label matches 'input.txt'. You must manually select the file.

classdef LaunchAppTest < matlab.uitest.TestCase
    properties
        Filename = 'input.txt'
    end
    methods(TestClassSetup)
        function checkFile(testCase)
            import matlab.unittest.constraints.IsFile
            testCase.assertThat(testCase.Filename,IsFile)
        end
    end
    methods (Test)
        function testInput(testCase)
            app = launchApp;
            testCase.addTeardown(@close,app.UIFigure)

            testCase.press(app.Button)

            testCase.verifyEqual(app.Label.Text,testCase.Filename)
        end
    end
end

Run the test. When the file selection dialog box appears, select input.txt to allow MATLAB to proceed with the test. Selecting any other file results in a test failure.

runtests("LaunchAppTest");

Running LaunchAppTest
.
Done LaunchAppTest
__________

Create Fully Automated Tests

To test the app without manual intervention, use the mocking framework. Modify the app to accept a file-choosing service instead of implementing it in the app (dependency injection).

Create a FileChooser service with an Abstract method that implements the file selection functionality.

classdef FileChooser
    % Interface to choose a file
    methods (Abstract)
        [file,folder,status] = chooseFile(chooser,varargin)
    end
end

Create a default FileChooser service that uses the uigetfile function for file selection.

classdef DefaultFileChooser < FileChooser
    methods
        function [file,folder,status] = chooseFile(~,varargin)
            [file,folder,status] = uigetfile(varargin{:});
        end
    end
end

Change the app to accept an optional FileChooser object. When called with no inputs, the app uses an instance of DefaultFileChooser.

function app = launchApp(fileChooser)
arguments
    fileChooser (1,1) FileChooser = DefaultFileChooser
end

f = uifigure;
button = uibutton(f,"Text","Input file");
button.ButtonPushedFcn = @(src,event) pickFile(fileChooser);
label = uilabel(f,"Text","No file selected");
label.Position(1) = button.Position(1) + button.Position(3) + 25;
label.Position(3) = 200;

% Add components to app
app.UIFigure = f;
app.Button = button;
app.Label = label;

    function file = pickFile(fileChooser)
        [file,~,status] = fileChooser.chooseFile("*.*");
        if status
            label.Text = file;
        end
    end
end

Make these modifications to LaunchAppTest:

• Change the class to inherit from both matlab.uitest.TestCase and matlab.mock.TestCase.

• Remove the properties block and the TestClassSetup methods block. Because the mock defines the output of the chooseFile method call, the tests do not rely on the existence of an external file.

• Change the testInput method to perform these actions:

  • Create a mock object from FileChooser.

  • Define mock behavior such that when the chooseFile method is called with the input "*.*", the outputs are the filename ('input.txt'), the current folder, and a selected filter index of 1. These outputs are analogous to the outputs from the uigetfile function.

  • Launch the app with the mockChooser object.

  • Press the button and verify the name of the selected file. These actions are the same as in the original test, but the mock assigns the output values, so you do not need to interact with the app to continue testing.

• To test the Cancel button, add a Test method named testCancel to perform these actions:

  • Create a mock object from FileChooser.

  • Define mock behavior such that when the chooseFile method is called with the input "*.*", the outputs are the filename ('input.txt'), the current folder, and a selected filter index of 0. These outputs are analogous to the outputs from the uigetfile function if a user selects a file and then chooses to cancel.

  • Launch the app with the mockChooser object.

  • Press the button and verify that the test calls the chooseFile method and that the label indicates that no file was selected.

classdef LaunchAppTest < matlab.uitest.TestCase & matlab.mock.TestCase
    methods (Test)
        function testInput(testCase)
            import matlab.mock.actions.AssignOutputs
            filename = 'input.txt';

            [mockChooser,behavior] = testCase.createMock(?FileChooser);
            when(behavior.chooseFile("*.*"),AssignOutputs(filename,pwd,1))

            app = launchApp(mockChooser);
            testCase.addTeardown(@close,app.UIFigure)

            testCase.press(app.Button)

            testCase.verifyEqual(app.Label.Text,filename)
        end

        function testCancel(testCase)
            import matlab.mock.actions.AssignOutputs

            [mockChooser,behavior] = testCase.createMock(?FileChooser);
            when(behavior.chooseFile("*.*"),AssignOutputs('input.txt',pwd,0))

            app = launchApp(mockChooser);
            testCase.addTeardown(@close,app.UIFigure)

            testCase.press(app.Button)

            testCase.verifyCalled(behavior.chooseFile("*.*"))
            testCase.verifyEqual(app.Label.Text,'No file selected')
        end
    end
end

Run the tests. The tests run to completion without manual file selection.

runtests("LaunchAppTest");

Running LaunchAppTest
..
Done LaunchAppTest
__________