MATLAB Answers

Using Load in a test methods makes the test pass

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Erik van Oene
Erik van Oene on 15 Oct 2019
Answered: Andy Campbell on 21 Oct 2019
The following test Passed! Why is that?
classdef minExample < matlab.unittest.TestCase
properties
end
methods(Test)
function test1(testCase)
% comment
save matlab
load matlab
verifyEqual(testCase,1,2);
end
end
end

  1 Comment

Erik van Oene
Erik van Oene on 16 Oct 2019
Run it using:
test = minExample
test.run
the outcome I get is:
ans =
TestResult with properties:
Name: 'minExample/test1'
Passed: 1
Failed: 0
Incomplete: 0
Duration: 0.1692
Totals:
1 Passed, 0 Failed, 0 Incomplete.
0.1692 seconds testing time.

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Answers (2)

Andy Campbell
Andy Campbell on 21 Oct 2019
Hi Erik,
The problem here is indeed the fact that the testCase is getting overwritten. Hence why if you assign the output of the load command to a structure the issue is not encountered. These steps are similar to something like the following:
classdef SomethingNotATestCase
methods
function verifyEqual(obj,varargin)
% do something else
end
end
end
Then inside the test, doing something like this:
classdef minExample < matlab.unittest.TestCase
methods(Test)
function test1(testCase)
testCase = SomethingNotATestCase
verifyEqual(testCase,1,2);
end
end
end
In both of these cases you have overwritten the testCase with something that is not the right thing to produce a test failure. This is perfectly allowable by the language. This is part of the reason why it is suggested to use the functional form of the load command, including with the output argument, because when you dont use the output argument you "poof" variables into the workspace, and this can overwrite existing variables. If you assign it to an output argument then you explicitly name your variable, and are much less likely to overwrite another variable unknowingly.
Hope that helps!
Andy

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per isakson
per isakson on 18 Oct 2019
Looks like a bug to me, however in programs one ought to use the functional form
S = load('matlab.mat');
In that case the test fails as expected.

  3 Comments

Erik van Oene
Erik van Oene on 18 Oct 2019
That is true, though, I don't want the variable of my 'old' workspace (saved in matlab.mat) to be loaded as a structure 'S'. So I changed the line you suggested to:
load('matlab.mat')\
which again makes this test Pass.
Problem is probably that 'testCase' is destroyed/overwritten when saving and loading it. Thought, if this is the reason, I expect any failure or error other than letting a test pass which clearly should not.
Erik
per isakson
per isakson on 18 Oct 2019
My memory fails me. However, when the current Matlab oop-stuff was introduced 10+ years ago there was a great deal of discussion about saving and loading objects.
per isakson
per isakson on 18 Oct 2019
Maybe this is of interest to you General-use object copy
Did you contact the Mathworks' tech-support?

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