_ASSERT - mkilgore/QB64pe GitHub Wiki

The _ASSERT statement can be used to perform tests in code that's in development, for debugging purposes.

_ASSERT condition[,]

• condition is the condition that must be met in order to consider the _ASSERT valid.
• Optional errorMessage$ is the message to be displayed in the console window if $ASSERTS:CONSOLE is used.
• If the condition is not met (that is, if it evaluates to 0), an error occurs ("_ASSERT failed on line #") and program execution stops.

• Version 1.4 and up.

Example: Adding test checks for parameter inputs in a function.

$ASSERTS:CONSOLE
 
DO
    a = INT(RND * 10)
    b$ = myFunc$(a)
    PRINT a, , b$
    _LIMIT 3
LOOP UNTIL _KEYHIT
 
FUNCTION myFunc$ (value AS SINGLE)
    _ASSERT value > 0, "Value cannot be zero"
    _ASSERT value <= 10, "Value cannot exceed 10"
 
    IF value > 1 THEN plural$ = "s"
    myFunc$ = STRING$(value, "*") + STR$(value) + " star" + plural$ + " :-)"
END FUNCTION

• $ASSERTS
• $CHECKING
• Relational Operations