How to test custom class with unit test class

Since, I'am very new to the topic of MatLab unit tests, I struggle with testing a custom MatLab class using a unit test class in a separate file.

Like I know from other programming languages, I would like to write a unit test (in a separate class) for a custom MatLab class. However, I do not see how to create an instance of / how to use my custom class within the test class.

Therefore, I would have the following questions, where I hope you can help me:

1. How do I properly create an instance of my custom class within the test class?
2. When I place my test class file in a sub-directory "tests/", how do I include the file of the my custom class?
3. Can you recommend a proper folder structure? Concrete, is it appropriate to place test classes in a sub-folder tests/

Thank you very much!

PS: Up to now - as minimal example - I have a file with a custom class MyMath.m:

classdef MyMath
    methods
        function obj = MyMath()
        end
        
        function outputArg = add(~, a1, a2)
            outputArg = a1+a2;
        end
    end
end

and a file with the test class MyMath_Test.m

classdef MyMath_Test < matlab.unittest.TestCase
    methods(TestClassSetup)
        % Shared setup for the entire test class
        my_math = MyMath();
    end
    
    methods(TestMethodSetup)
        % Setup for each test
    end
    
    methods(Test)
        % Test methods
        
        function unimplementedTest(testCase)
            res = my_math.add(4,5);
            testCase.verifyEqual(res, 9)
        end
    end 
end

Running Tests via Matlab GUI Buttons, results in the error:

>> runtests("MyMath_Test")

Running MyMath_Test

================================================================================

Error occurred while setting up or tearing down MyMath_Test.

As a result, all MyMath_Test tests failed and did not run to completion.

---------

Error ID:

---------

'MATLAB:TooManyInputs'

--------------

Error Details:

--------------

Error using MyMath_Test/MyMath

Too many input arguments.

================================================================================

Answer 1

[Jatin]

Hi @Christian,

To correctly create an instance of your custom class within the test class, define a property in the test class that is accessible to all test methods. This can be achieved using the "properties" block.

If your test class is located in a subdirectory, ensure that directory is included in MATLAB's path by using the "Add to Path" option.

Organizing your test cases in a subdirectory named "tests/" is a good practice, as it helps keep your code well-organized.

Here is a correct example of a unit test class for the custom class you mentioned.

classdef MyMath
    methods
        function obj = MyMath()
        end
        
        function outputArg = add(~, a1, a2)
            outputArg = a1 + a2;
        end
    end
end

Test class:

classdef MyMath_Test < matlab.unittest.TestCase
    properties
        myMath % Property to hold an instance of MyMath
    end

    methods(TestMethodSetup)
        function createMyMathInstance(testCase)
            % Setup for each test - create an instance of MyMath
            testCase.myMath = MyMath();
        end
    end
    
    methods(Test)
        function testAddMethod(testCase)
            % Test the add method
            res = testCase.myMath.add(4, 5);
            testCase.verifyEqual(res, 9);
        end
    end
end

Kindly go through the below documentation for more on "Ways to right unit tests":

https://www.mathworks.com/help/matlab/matlab_prog/ways-to-write-unit-tests.html

Hope this helps!

Answer 2

[Deepak Gupta]

Hi,

Methods keyword is used to define a wrapper for all the method which need to run during class setup or method setup or test themselve, just like you have done for methods(Test) . Here is updated code, with few changes.

classdef MyMath_Test < matlab.unittest.TestCase
    properties
        my_math % You have defined your class object in a TestClassSetup. It needs to be declared first
        %  as a property I would rather suggest you to create class object
        %  inside test method or TestMethodSetup so object gets created for
        %  each run individually.
    end

    methods(TestClassSetup)
        % To answer your question, regarding where to place tests. You can
        % place them anywhere. I would suggest you create a separate
        % directly for tests from source. You can use path fixture to add
        % source path for your test to use at runtime. Any function defined
        % as TestClassSetup will only run once at the start of this test.
        function pathFixture(testCase)
            import matlab.unittest.fixtures.PathFixture
            testCase.applyFixture(PathFixture("SourcePath\Custom_Class"))
        end
    end
    
    methods(TestMethodSetup)
        % Any function defined as TestMethodSetup will run for each test
        % point and will create and destruct objects automatically after
        % test point is complete
        function CreateClassObject(testCase)
            testCase.my_math = MyMath();
        end
    end
    
    methods(Test)
        % Test methods
        function unimplementedTest(testCase)
            res = testCase.my_math.add(4,5);
            testCase.verifyEqual(res, 9)
        end
    end 
end

If you create object inside test method itself it will be like this:

classdef MyMath_Test2 < matlab.unittest.TestCase
    methods(TestClassSetup)
        function pathFixture(testCase)
            import matlab.unittest.fixtures.PathFixture
            testCase.applyFixture(PathFixture("SourcePath\Custom_Class"))
        end
    end
    methods(Test)
        % Test methods
        function unimplementedTest(testCase)
            my_math = MyMath();
            res = my_math.add(4,5);
            testCase.verifyEqual(res, 9)
        end
    end 
end

Cheers,

Deepak

[Christian]

Dear @Deepak Gupta,

thank you very much for your fast answer and all the interesting background/additional information.

Answer 3

[Jack]

It looks like you're facing issues with setting up your unit tests in MATLAB. To create an instance of your custom class in the test class, make sure you initialize it in a method rather than directly in the TestClassSetup. Also, ensure that your test class file is in the same directory or correctly referenced if in a sub-directory. Much like how you might strategize in iq test, a common structure is to have a src/ folder for your classes and a tests/ folder for your test classes. This way, you can easily manage and run your tests. Good luck!