assert_checkerror

Parameters

instr:

a 1-by-1 matrix of strings, an expression to evaluate

expectedmsg :

a string or a string vector, the error message to be produced

expectederrnb :

a 1-by-1 matrix of doubles, integer values, the error number (default expectederrnb=[]).

a1 :

an extra localization argument, passed to the msprintf function.

flag :

a 1-by-1 matrix of boolean, %t if the correct error message was produced, %f if not

errmsg :

a 1-by-1 matrix of strings, the error message. If flag==%t, then errormsg=="". If flag==%f, then errmsg contains the error message.

Description

If the expression does not generate an error, then assert_checkerror generates an error. Performs silently if the evaluated expression generates the expected error message.

If the error message expectedmsg is provided and is not the empty matrix [], we check that the generated error number matches the expected one. If the error number expectederrnb is provided and is not the empty matrix [], we check that the generated error number matches the expected one. If the error message expectedmsg and the error number expectederrnb cannot be equal to the empty matrix [] at the same time: at least one of them must be provided.

The string matching is strict string equality: no pattern or regular expression can be used.

If the error message is not expected or the error number is not expected,

• if the errmsg output variable is not used, an error is generated,

• if the errmsg output variable is used, no error is generated.

The goal of this function is to enable the tester to check the error cases in a simplified framework. Checking the error messages of a function has the following advantages:

• it checks that the correct error is generated when needed,

• it checks that the error message is correctly formatted,

• it checks that the error message is correctly localized.

The expected message can be a localized message. In this case, the message is compared with the output of the gettext function, and depends on the local language. The extra argument a1 can be used for this purpose, for example to format the localized message. All the extra arguments a1, a2, ... are automatically passed to the msprintf function before being compared to the computed error message.

Examples

We give several examples of using the assert_checkerror function. We first have to define a function to be tested.

The following function f generates an error when the number of input arguments in wrong or the type of x is wrong.

function y=f(x)
    [lhs, rhs] = argn()
    if ( rhs <> 1 ) then
        lstr = gettext("%s: Wrong number of input argument: %d expected.\n")
        errmsg = msprintf ( lstr , "f" , 1 )
        error(errmsg)
    end
    if ( typeof(x) <> "constant" ) then
        lstr = gettext("%s: Wrong type for argument #%d: Matrix expected.\n")
        errmsg = msprintf ( lstr , "f" , 1 )
        error(errmsg,123456789)
    end
    y = x
endfunction

Our task is to check the error messages produced by this function. The two following tests pass: the error message is the expected one. We let assert_checkerror manage the localization, by providing only the localized message and the extra parameter "f" (the name of the function) and 1 (the index of the input argument). These two extra parameters are used by assert_checkerror to format the message and to convert the "%s" and "%d" formats into their actual values.

lcl1 = "%s: Wrong number of input argument: %d expected.\n";
assert_checkerror ( "y = f()" , lcl1 , [] , "f" , 1);

lcl2 = "%s: Wrong type for argument #%d: Matrix expected.\n";
assert_checkerror ( "y = f(""a"")" , lcl2 , [] , "f" , 1);

On the other hand, if we make the assumption that the current locale language is english, we could as well use the following statement. But this is not a recommended practice, since the test will fail if the current locale is French, for example.

assert_checkerror ( "y = f()" , "f: Wrong number of input argument: 1 expected." );

In the following test, we also check the error number.

lcl1="%s: Wrong number of input argument: %d expected.\n";
assert_checkerror ( "y=f()" , lcl1 , 10000     , "f" , 1);

lcl2 = "%s: Wrong type for argument #%d: Matrix expected.\n";
assert_checkerror ( "y=f(""a"")" , lcl2 , 123456789 , "f" , 1);

The two following tests fail.

assert_checkerror ( "y = f()" , "oups" );

msg1 = msprintf(gettext("%s: Wrong number of input argument: %d expected.\n"), "f", 1);
assert_checkerror ( "y = f()" , msg1 , 12 );

When errmsg is given as output argument, no error is generated, as in the following example. Notice the content of the flag and errmsg variables.

// A test which pass: flag is %t, errmsg is empty
msg1 = msprintf(gettext("%s: Wrong number of input argument: %d expected.\n"), "f", 1);
[flag, errmsg] = assert_checkerror ( "y = f()" , msg1 )

// A test which fail: flag is %f, errmsg is not empty
[flag, errmsg] = assert_checkerror ( "y = f()" , "oups" )

The messages in the two following tests are localized, so that they can work whatever the current language is. Instead of using the extra parameter a1, we directly localize the message, which is less short, but is a perfectly valid code.

msg1 = msprintf(gettext("%s: Wrong number of input argument: %d expected.\n"), "f", 1);
assert_checkerror ( "y = f()" , msg1 );

msg2 = msprintf(gettext("%s: Wrong type for argument #%d: Matrix expected.\n"), "f", 1);
assert_checkerror ( "y = f(""a"")" , msg2 );

It may happen that we want to just test the error number, but not the error message. The following script just checks that the generated error number is 123456789 when the first argument is not a matrix of doubles: we do not check the error message.

assert_checkerror("f(""foo"")", [], 123456789);

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