I have another one:

For several test cases I have to suppress the display of progress (otherwise the tests would run much slower). To do that, I override performTest to catch the relevant exceptions/notifications and mute them. I need that in multiple test case classes, but I do not want to provide the progress suppressing with an abstract test superclass. So I created a trait that contains this performTest override. Test cases that need the progress muted can mix that in by using the trait.

Why don't I want the abstract superclass? Because I have two more such traits for test cases: one that provides additional assert methods for a certain type of object, and one that provides a method for suppressing change notifications so the changes file is not cluttered that much when the tests run. As traits I can mix in and combine these into test case classes when they are required.

The latter mentioned trait would benefit from a traits implementation with state, though.

Am So., 31. März 2019 um 21:21 Uhr schrieb Levente Uzonyi <leves@caesar.elte.hu>:
On Sat, 30 Mar 2019, David T. Lewis wrote:

> Changing the subject line to focus on Levente's question.
>
> On Thu, Mar 28, 2019 at 06:43:11PM +0100, Levente Uzonyi wrote:
>>
>> What are the current use cases for traits?
>
> In order to experiment with Git based repositories, I have loaded the
> Tonel package from the github repositories of Jakob Reschke.
>
>       Installer ensureRecentMetacello.
>       (Smalltalk classNamed: #Metacello) new
>          repository: 'github://j4yk/tonel:squeak';
>          baseline: 'Tonel';
>          load.
>
> This brings in the FS-AnsiStreams package, which uses traits.
>
> Having traits in Squeak allows me to load this package.

I haven't tried your snippet and I don't know which version of FS depends
on Traits, but the one on SqueakSource definitely does not.
Btw, Traits can be flattened, so it's possible to make it loadable into
images with no Trait support.

So far all use cases of Traits in this thread (and its parent) were about
interfaces. Squeak doesn't have a concept for that, and Traits are
definitely more than just simple interfaces (as long as you don't want to
interface state). Perhaps we need interfaces instead of traits.

Levente

>
> Dave