kicad-developers team mailing list archive

[Jon Evans <jon@xxxxxxxxxxxxx>]

Hi John,

That makes sense!  Thanks for the detailed explanation.

-Jon

On Mon, Apr 29, 2019 at 8:28 AM John Beard <john.j.beard@xxxxxxxxx> wrote:

> On 29/04/2019 12:41, John Beard wrote:
>
> > Then you might start running into consistency issues with multiple
> > users of A_C getting different answers.
>
> Notably, there is a specific case that illustrates where global state
> can cause Bad Things (TM) right now: unit tests.
>
> Say you had a mutable ADVANCED_CFG, and you have a test suite like this:
>
>      BOOST_AUTO_TEST_CASE( Test1 )
>      {
>          CONNECTIVITY_FOO thing;
>          ADVANCED_CFG::GetCfg().m_whatever = true; // default false
>
>          thing.Frobnicate(); // cares about m_whatever
>      }
>
>      BOOST_AUTO_TEST_CASE( Test2 )
>      {
>          // what is ADVANCED_CFG::GetCfg().m_whatever?
>          // It depends on the test case ordering.
>          // Test2 does not *have* to come second, and might even be
> concurrent
>          // so AC::m_whatever could even change *during* this test
>
>          CONNECTIVITY_FOO thing;
>          thing.Frobnicate(); // what will this do?
>      }
>
> Also, if core functions depend on A_C, it's very hard to test them with
> good coverage. It's better to pass the A_C as a higher level parameter,
> so you can do this:
>
>      BOOST_AUTO_TEST_CASE( TestWithFeatureOn )
>      {
>          bool enable_feature = true;
>          CONNECTIVITY_FOO thing( enable_feature );
>          thing.Frobnicate(); // test with feature
>      }
>
>      BOOST_AUTO_TEST_CASE( TestWithFeatureOff )
>      {
>          bool enable_feature = false;
>          CONNECTIVITY_FOO thing( enable_feature );
>          thing.Frobnicate(); // test without feature
>      }
>
> If CONNECTIVITY_FOO only used A_C internally, you cannot test the
> feature reliably as it depends on the config the user has set.
>
> Cheers,
>
> John
>