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rspec users.. how do _you_ explain the difference between `subject` and `let`?
@esparta@ruby.social@kerrizor both are kind of the same, but IMO it's about semantics.
- `subject` is related to point and to name the system under test.
- `let` is related to making available a value to the context.
You can use both to perform the expectations, but semantically it is more "natural" to use the subject.
One difference is about when they are evaluated: all the `subject` are lazily evaluated, and some `let` can be _immediate_ if use `let!`
@kerrizor ... cont ...
re:
> rspec users.. how do _you_ explain the difference between `subject` and `let`?
Another difference: `subject` can be (ab)used to perform one-liners on #rspec expectations:
subject { Validator.call(obj) }
context 'with valid obj' do
let (:obj) { 42 }
it { is_expected.to be_valid }
end
context 'with invalid obj' do
let(:obj) { 18 }
it { is_expected.to be_failure }
end
@esparta subject can be eagerly evaluated as well with subject! (Same as let!)
@jasonkarns ohh right!
True. True.
Forgot about that, perhaps since I never use `subject!` and actually never seen in the codebases I've been working on.
@esparta agree. seeing it actually used would probably be a sign of a code smell if the subject needed to be triggered prior to example actually running 