How to #let a JSON file in RSpec on Rails

EDIT:

The solution seems to start with describe KayNein::Twitter do instead of RSpec.describe KayNein::Twitter do.

describe KayNein::Twitter do

RSpec.describe KayNein::Twitter do

Why is this the case?

Rails 5.2.1
Ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]

Original Question

I have a class that initializes with a JSON file:

module KayNein
class Twitter < Handler

def initialize(json_file)
@website_hash = JSON.parse(json_file)
end


And I'm trying to write an RSpec:

RSpec.describe KayNein::Twitter do
let (:json_file) File.read(PATH_TO_FILE)
context "Initialized" do
subject = KayNein::Twitter.new(json_file)
end
end


But RSpec gives me this error:

An error occurred while loading ./spec/app/kay_nein/sites/twitter_spec.rb.
Failure/Error: subject = KayNein::Twitter.new(json_file)
`json_file` is not available on an example group (e.g. a `describe` or `context` block). It is only available from within individual examples (e.g. `it` blocks) or from constructs that run
in the scope of an example (e.g. `before`, `let`, etc).
# ./spec/app/kay_nein/sites/twitter_spec.rb:8:in `block (2 levels) in <top (required)>'
# ./spec/app/kay_nein/sites/twitter_spec.rb:7:in `block in <top (required)>'
# ./spec/app/kay_nein/sites/twitter_spec.rb:5:in `<top (required)>'


What am I doing wrong?

Even this gives me an error, so it has nothing to do with the file:

RSpec.describe KayNein::Twitter do
let (:json_file) "Hello world"
context "Initialized" do
subject = KayNein::Twitter.new(json_file)
end
end


it "returns a file" do write your test here end

3 Answers
3

Can you try something like this ?

let(:file) File.read(File.join('spec', 'fixtures', 'public', filename))

describe "File" do
it "should be a file" do
expect(file).to be_a File
end

it "should initialize and read the contents"
initialize_file = KayNein::Twitter.new(file)
expect(response.body["key"]).to eq(..)
end
end


Rspec.describe

We have two ways to DRY up tests (before and let) that share an intersecting purpose, to create variables that are common across tests. For common variable instantiation, the Ruby community prefers let, and while before is often used to perform actions common across tests.

when you use the context you can initialize the let inside the context block like this, will work

describe KayNein::Twitter do
context "Initialized" do
let (:json_file) File.read(PATH_TO_FILE)
subject = KayNein::Twitter.new(json_file)
end
end

otherwise if you don't want to use context, can try this way

describe KayNein::Twitter do
let (:json_file) File.read(PATH_TO_FILE)
it "Initialized" do
subject = KayNein::Twitter.new(json_file)
end
end


You can think of let as defining accessors. And those accessors are available only inside example blocks it or specify.

let

it

specify

You are trying to use json_file (defined in let) inside a context. And this is exactly what the error message is trying to tell you:

json_file

context

json_file is not available on an example group (e.g. a describe or
context block). It is only available from within individual examples
(e.g. it blocks) or from constructs that run in the scope of an
example (e.g. before, let, etc).

json_file

describe

context

it

before

let

You can fix it like this:

RSpec.describe KayNein::Twitter do
let (:json_file) File.read(PATH_TO_FILE)
context "Initialized" do
specify do # it instead of specify also works
subject = KayNein::Twitter.new(json_file)
expect(subject).not_to be_nil # this is just an example, not needed to
# get rid of the issue
end
end
end


or even better - define subject outside of example block (for reusability etc) like this:

RSpec.describe KayNein::Twitter do
let (:json_file) File.read(PATH_TO_FILE)
subject KayNein::Twitter.new(json_file)
context "Initialized" do
specify do # it instead of specify also works
expect(subject).not_to be_nil # this is just an example, not needed to
# get rid of the issue
end
end
end


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