Test database records with rspec

Question

Where am I going wrong?

 describe '#update' do
    let(:new_name) { Faker::Lorem.word }
    let(:request) { patch :update, id: parent_folder.id, folder: { name: new_name, parent_id: nil, user_id: user.id } }

    it 'should change the name' do
      expect{ request }.to change(parent_folder.reload,:name).from(parent_folder.name).to(new_name)
    end

    it 'does work gadnammit' do
      ap parent_folder.reload.name #=> e.g. aqua
      request
      ap parent_folder.reload.name #=> e.g. hortis
    end
  end

The result of 'should change the name' is

Failure/Error: expect{ request }.to change(parent_folder.reload,:name).from(parent_folder.name).to(new_name)# @new_name
expected #name to have changed from "maxime" to "jimmies", but did not change

And yet 'does work gadnammit' logs two different names:

All examples were filtered out; ignoring {:focus=>true}
F."omnis"
"jimmies"

Failures:

1) FoldersController#update should change the name
     Failure/Error: expect{ request }.to change(parent_folder.reload,:name).from(parent_folder.name).to(new_name)# @new_name
       expected #name to have changed from "maxime" to "jimmies", but did not change
     # ./spec/controllers/folders_controller_spec.rb:62:in `block (3 levels) in <top (required)>'

Also, when you're using the let helper with Faker, I am aware you get a new result each time the variable it creates is called, which could be giving the illusion the name is changing in the 'does work gadnammit' spec. However, changing it to a hardcoded string yields no difference:

let(:new_name) { "stagnant" }

Also, this spec:

it 'should make database queries' do
  expect{ request }.to make_database_queries 
end

passes so I really think it is working...

SELECT  "users".* FROM "users"  WHERE "users"."id" = 1  ORDER BY "users"."id" ASC LIMIT 1
SELECT  "folders".* FROM "folders"  WHERE "folders"."user_id" = ? AND "folders"."id" = ? LIMIT 1
SAVEPOINT active_record_1
UPDATE "folders" SET "name" = ?, "updated_at" = ? WHERE "folders"."id" = 1
RELEASE SAVEPOINT active_record_1

(make_database_queries matcher courtesy of db-query-matchers gem)

TL;DR Why isn't

expect{ request }.to change(parent_folder.reload,:name).from(parent_folder.name).to(new_name)

working?

Peter Alfvin · Accepted Answer · 2014-07-01 13:22:45Z

2

The parameter parent.folder.rename is evaluated at the time change is called. It doesn't (and can't) get re-evaluated after the block-under-test is executed. This most likely explains why name called on the resulting object does not change.

If you want an expression to be re-evaluated before and after the execution of the block under test, you need to pass change a block as in:

change { parent.folder.reload }.from(...).to(...)

The "parameter" version of change works when the first parameter remains unchanged (e.g. a constant) and the value returned by the method associated with the second parameter changes.

answered Jul 1, 2014 at 13:22

Peter Alfvin

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3 Comments

Starkers Over a year ago

Thanks peter! Shame it doesn't read nearly as well as expect{ request }.to change... Why is it that expect{ delete :destroy, id: child_folder.id }.to change(Folder, :count).by(-1) works? Surely that must evaluate Folder.count before and after the request is executed, so why doesn't it work when querying an actual record?

Starkers Over a year ago

Right, I'm going to be honest I'm a bit confused. expect { employee.develop_great_new_social_networking_app }.to change(employee, :title).from("Mail Clerk").to("CEO") from rubydoc.info/github/rspec/rspec-expectations/RSpec/… very closely matchers what I want to and yet this doesn't work? Example please :)

Starkers Over a year ago

I had to ask this question a second time. Didn't notice the curly braces, ignore me :P

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