How can I make my test find a second function in a neighboring file?

I inherited some matlab files and I want to write tests for them.

Each file contains multiple function declarations.

It seems like I can only access the top-level function. How do I make tests for the other functions?

(I did the OnRamp course...)

File: toBeTested.m

function value = toBeTested(x)
    value = toBeTested2(x) - 1; 
end
 
function value = toBeTested2(x)
    value = x; 
end

File: toBeTestedTest.m

function tests = toBeTestedTest
  tests = functiontests(localfunctions);
end 
function setupOnce(~)
    addpath .. .
end
function test1(testCase)
    which test1
    which toBeTested   % this is found...
    verifyEqual(testCase, 1, toBeTested(2));
end
function test2(testCase)
    which test2
    which toBeTested2  % this says it can't be found :?(
    verifyEqual(testCase, 2, toBeTested2(2));  % This fails, with an error
end

When I open the file in the LiveEditor, it prompts me with a RunTests button.

The test1 passes. test2 fails with:

Error occurred in toBeTestedTest/test2 and it did not run to completion.
    ---------
    Error ID:
    ---------
    'MATLAB:UndefinedFunction'
    --------------
    Error Details:
    --------------
    Undefined function 'toBeTested2' for input arguments of type 'double'.
    
    Error in toBeTestedTest>test2 (line 18)
        verifyEqual(testCase, 2, toBeTested2(2));

Answer 1

[matquest]

See the accepted answer to this related question: Multiple functions in one .m file, but the upshot is that unfortunately you cannot do what you're trying to.

I actually have been in a similar situation recently and there are two main options that I was able to identify:

1. Convert the functions to classes. Then you can create a "unit_tests" function that you can call
2. Change the function that has the same name as the file (e.g., if your file is named "complicated_stuff.m" the function header would look like function output = complicated_stuff([args]) to use varargin. Then do potentially horribly inelegant stuff to check the number of inputs and redirect to a unit_tests function at the bottom.