Customize assertions

Is there a way to add some custom assertions to t existing ones?

I would like to add those basic ones: — t.instanceof(object, clazz) — t.length(array, length) — t.members(array, item, item) — t.includes(string, substring)

I guess t.context can be used, but feels cumbersome. And maybe, those assertions can be considered to be added to ava core.

[sindresorhus]

Not at the moment, but your needs can be solved with the existing methods:

t.true(object instanceof clazz);
t.is(array.length, length);
t.true(array.every(x => [item, item].includes(x)));
t.true(string.includes(substring));

You can already use any external assertion library. The only caveat is that t.plan() doesn’t work.

[sotojuan]

I guess the problem is that it’s a slippery slope. These kind of extra assertions are better in userland as separate modules, functions, or snippets. I personally don’t see anything wrong with the code block in the last comment but you could make it look “prettier” by abstracting those functions away. That way you can use your own custom logic as well.

The smaller core AVA is, the easier it is to use.