rspec users - Dec 2012 - Augmenting a previous 'let' value

I find myself wanting to do something like this, and I''m curious to
hear what others think of this pattern.

describe "a hash with two values" do
  let(:hsh) {{ xxx: 1, yyy: 2 }}

  context "with a third value added" do
    alias _hsh hsh
    let(:hsh) { _hsh.merge(zzz: 3) }

    it "should contain all three values" do
      hsh.should == { xxx:1, yyy:2, zzz:3 }
    end
  end
end

The alias there is a workaround, ideally I''d like hsh to reference the
previous value when inside that block : let(:hsh) { hsh.merge(zzz: 3)
} , but with the current implementation that gives infinite recursion.

Another way is to use a before block, but I don''t like the mixing of
let and before in this case.

describe "a hash with two values" do
  let(:hsh) {{ xxx: 1, yyy: 2 }}

  context "with a third value added" do
    before { hsh.merge!(zzz: 3) }

    it "should contain all three values" do
      hsh.should == { xxx:1, yyy:2, zzz:3 }
    end
  end
end

I don''t want to use a different name, because I have shared examples
that reference it. I know there are ways to side step the issue.

Have you used something like this before? Would you consider it bad practice?

- Arne

If you declare :hsh in two peer context (neither inside the other), then
your shared group does the right thing: it demands the existence of :hsh
and blows up when it doesn''t exist. Better design, no?



On Fri, Dec 21, 2012 at 9:24 AM, Arne Brasseur <arne.brasseur at
gmail.com>wrote:
> I find myself wanting to do something like this, and I''m curious
to
> hear what others think of this pattern.
>
> describe "a hash with two values" do
>   let(:hsh) {{ xxx: 1, yyy: 2 }}
>
>   context "with a third value added" do
>     alias _hsh hsh
>     let(:hsh) { _hsh.merge(zzz: 3) }
>
>     it "should contain all three values" do
>       hsh.should == { xxx:1, yyy:2, zzz:3 }
>     end
>   end
> end
>
> The alias there is a workaround, ideally I''d like hsh to reference
the
> previous value when inside that block : let(:hsh) { hsh.merge(zzz: 3)
> } , but with the current implementation that gives infinite recursion.
>
> Another way is to use a before block, but I don''t like the mixing
of
> let and before in this case.
>
> describe "a hash with two values" do
>   let(:hsh) {{ xxx: 1, yyy: 2 }}
>
>   context "with a third value added" do
>     before { hsh.merge!(zzz: 3) }
>
>     it "should contain all three values" do
>       hsh.should == { xxx:1, yyy:2, zzz:3 }
>     end
>   end
> end
>
> I don''t want to use a different name, because I have shared
examples
> that reference it. I know there are ways to side step the issue.
>
> Have you used something like this before? Would you consider it bad
> practice?
>
> - Arne
> _______________________________________________
> rspec-users mailing list
> rspec-users at rubyforge.org
> http://rubyforge.org/mailman/listinfo/rspec-users
>


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J. B. (Joe) Rainsberger :: http://www.myagiletutor.com ::
http://www.jbrains.ca ::
http://blog.thecodewhisperer.com
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