RELEASE LiveCode 6.6 DP1

[Trevor DeVore]

On Sunday, February 16, 2014, Peter Haworth <pete at lcsql.com> wrote:

> The assert command seems to have appeared out of nowhere.  Is it on any
> plan that anyone has seen?


I believe it was added in order to aid with adding test coverage to
LiveCode. At least I seem to recall reading something about that in some
commit notes on GitHub.


> Anyway, with assert:
> -----------------------------
> --Test Harness using assert
> -----------------------------
> command test1
>   <do test commands>
>    assert .....
> end test1
>
> command test2
>   <do test commands>
>    assert .....
> end test2
>
> on assertMessage
>   switch phandler
>      case "test1"
>          <log stuff>
>          break
>       case "test2"
>          <log stuff>
>          break
>    end switch
> end assertMessage
> ------------------------------


I wouldn't have a switch statement like that in assert message. Why not
just stop execution on every error? The developer sees the error, knows
exactly which line to check (your code could even open the script editor
and position the cursor at the exact spot), makes the fix, and then runs
the tests again.

I don't see how you could do that with assert since the main way to
> identify which test failed is by the handlername parameter so it would be
> one test per test handler unless you wanted to rely on the line parameter
> which doesn't feel very safe.  I guess you could stop the tests by setting
> a script local or global variable but seems unnecessarily complicated.
>

Can't you just stop the tests with 'exit to top'?

I think a useful implementation of assertMessage is to log the error, open
the script editor, and then stop execution with 'exit to top'. If a
developer runs their test suite prior to every release they have a quick
way of finding any errors that break their preconditions defined by the
asserts and fixing them.

Another use would be to just log a bunch of messages that the developer
could go back and check. Perhaps assert could be improved upon with the
ability to tell it to stop execution if the assertion fails:

Assert 'condition' with exit to top

The engine would send the assertMessage and then halt execution
automatically.

Ultimately I think assert gives us a richer way of expressing what it is we
are doing in the code - testing that something behaves as it is intended.
Personally I find assert more descriptive when reading through code (assert
is commonly used in other languages).

-- 
Trevor DeVore