MATLAB: How to create a unit testing mocking framework for function files

MATLAB

We have 'first.m' file with function "first" inside and 'second.m' file with function "second" inside. Both are basic scripts with no OOD. From function "first" we call function "second". I want to fake behavior of function "second" without having to change the file first.m. This is to be done for the unit testing of 'first.m'.

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Mocking framework is typical in a lot of testing frameworks. Unfortunately, the methods mentioned in the link below are designed to work on objects and not functions.

https://www.mathworks.com/help/matlab/mocking-framework.html

To mock function files, there are two ways that I can think of:

1. To create a mock function for 'second', an easy way would be to create a sub folder in the parent folder having 'first' and 'second', and add the newly created subfolder to the MATLAB path using 'addpath', right before the function call to 'second' from 'first'.

This subfolder can have a dummy 'second' function which returns only stub or mock values which would enable 'first' to continue execution.

2. The second way is to use 'PathFixture', while writing the tests, which is a fixture for adding a folder to the MATLAB path.

https://www.mathworks.com/help/matlab/ref/matlab.unittest.fixtures.pathfixture-class.html

This will be easier to explain with an example. Please find attached 4 files, 'first.m', an actual 'second.m', the dummy 'second.m' and the unit test file 'tFirst.m', which tests 'first.m', with dummy 'second.m'

If 'home' is my current working directory, then the location of the files are as

\home\tFirst.m

\home\src\first.m

\home\src\second.m (This is the actual 'second.m')

\home\mocks\second.m (This is the dummy 'second.m')

Considering '\home' as the Current directory, the folder '\home\src' has to be added to the path first.

As can be seen in the file 'tFirst.m', adding the two lines of code

import matlab.unittest.fixtures.PathFixture;
testCase.applyFixture(PathFixture(fullfile(pwd,'mocks')));

sets up the fixture such that when 'second' is called from 'first' during the unit test, the dummy 'second' in '\home\mocks' is called.

The dummy 'second.m' must be set up to return stub values and avoid execution of the actual 'second.m'.

Related Solutions

MATLAB: How to create custom code suggestions for class functions in MATLAB live scripts

It is possible to use code suggestions with ordinary class member functions.

The only difference is you must account for the first method argument being a reference to the class.

The first argument passed to a MATLAB class member function is a reference to the object. In that sense, the following two function calls are equivalent:

classObj.func(val)
func(classObj, val)

For more information on this, please see:

https://www.mathworks.com/help/matlab/matlab_oop/specifying-methods-and-functions.html

When creating the 'functionsSignatures.json', be sure to include an input for the class object.

Here is an example 'functionsSignature.json' snippet for a class which has static and ordinary member functions:

{
      "BasicClass.BasicClass":
      {
          "inputs":
          [
              {"name":"inputVal", "kind":"required", "type":["numeric"], "purpose":"Constructor with value to initalize with."}
          ]
      },
      "BasicClass.printString":
      {
          "inputs":
          [
              {"name":"inputString", "kind":"required", "type":["string"], "purpose":"String to print to screen."}
          ]
      },
      "BasicClass.multBy":
      {
          "inputs":
          [
              {"name":"obj", "kind":"required", "type":["BasicClass"], "purpose":"BasicClass object to run function on."},
              {"name":"multVal", "kind":"required", "type":["numeric"], "purpose":"Will multiply the initial value by multVal."}
          ]
      }
  }

In the example, "printString" is static, while "multBy" is a traditional member function.

Moreover, once you have written the JSON file, you can also verify it by executing the following command in the MATLAB Command Window:

>> validateFunctionSignaturesJSON

You will find more information about this function in the documentation:

https://www.mathworks.com/help/matlab/ref/validatefunctionsignaturesjson.html

MATLAB: Do I see error failed since claNotify was not mocked while mocking axes

The names of methods to add to mock in 'createMock' function do not include 'cla'.

I am assuming that there is typo there and you intended to use 'cla' instead of 'clo'-

[mockedAxes, behavior] = testCase.createMock(...

'AddedMethods',["isgraphics" "claNotify" "clo"]);

Replace 'clo' with 'cla' and you should be able to call 'cla' on mocked axes.

This will resolve your problem.

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Related Solutions

MATLAB: How to create custom code suggestions for class functions in MATLAB live scripts

MATLAB: Do I see error failed since claNotify was not mocked while mocking axes

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