How can I access a record of the Command Window using MATLAB Grader?

I have asked learners to write a function that displays some messages to the Command Window.

In MATLAB I know I can use the diary function to access a record of the Command Window text, like this:

% Start the diary
diary CommandLog

% run the learner solution here

% Access the log then assess if correct
printOuts = fileread('CommandLog')

For some reason, this comes up as empty char in MATLAB Grader. Is there an alterative?

[Cris LaPierre]

Could you share an example? How many outputs does their function create? How are they created?

[IFM]

How the learners display the messages is up to them. Here are some MWE functions that might be produced by the students.

function y = myFunction(x)
    fprintf('Num #1 is passed')
    y=32;
end

%% Second example to show they can print out in any way
function y = myFunction2(x)
    s=sprintf('check #1 passed')
    disp(s)
    y=64;
end

And here is what I tried in the MATLAB Grader Testing Suite (just on a function with one output for ease of testing):

diary CommandLog.out

% Run learner solution.
x = 1;
y = myFunction(x); 

% Run reference solution.
yRef = reference.myFunction(x); 

% Compare.
assessVariableEqual('y', yRef);

% Access "diary" to see all stuf fin Command Window.
printOuts = fileread('CommandLog.out');
whos printOuts

if isempty(printOuts)
    error('Your function does not display any messages to the Command Window')
end

However the test fails regardless, even if myFunction is displaying something. "printOuts" is always empty.

Answer 1

[Cris LaPierre]

One workaround could be to write an assessment test that calls the functions using evalc. This captures the command window output in a variable you can then use for assessment.

[IFM]

Great, this looks like it will work. Thanks!