How to check for a JSON response using RSpec?

Question

I have the following code in my controller:

format.json { render :json => { 
        :flashcard  => @flashcard,
        :lesson     => @lesson,
             


        

Answer 1

For Your JSON response you should parse that response for expected results For Instance: parsed_response = JSON.parse(response.body)

You can check other variables which is included in response like

expect(parsed_response["success"]).to eq(true)
expect(parsed_response["flashcard"]).to eq("flashcard expected value")
expect(parsed_response["lesson"]).to eq("lesson expected value")
expect(subject["status_code"]).to eq(201)

I prefer also check keys of JSON response, For Example:

expect(body_as_json.keys).to match_array(["success", "lesson","status_code", "flashcard"])

Here, We can use should matchers For expected results in Rspec

Answer 2

There's also the json_spec gem, which is worth a look

https://github.com/collectiveidea/json_spec

Answer 3

When using Rails 5 (currently still in beta), there's a new method, parsed_body on the test response, which will return the response parsed as what the last request was encoded at.

The commit on GitHub: https://github.com/rails/rails/commit/eee3534b

Answer 4

If you want to take advantage of the hash diff Rspec provides, it is better to parse the body and compare against a hash. Simplest way I've found:

it 'asserts json body' do
  expected_body = {
    my: 'json',
    hash: 'ok'
  }.stringify_keys

  expect(JSON.parse(response.body)).to eql(expected_body)
end

Answer 5

I found a customer matcher here: https://raw.github.com/gist/917903/92d7101f643e07896659f84609c117c4c279dfad/have_content_type.rb

Put it in spec/support/matchers/have_content_type.rb and make sure to load stuff from support with something like this in you spec/spec_helper.rb

Dir[Rails.root.join('spec/support/**/*.rb')].each {|f| require f}

Here is the code itself, just in case it disappeared from the given link.

RSpec::Matchers.define :have_content_type do |content_type|
  CONTENT_HEADER_MATCHER = /^(.*?)(?:; charset=(.*))?$/

  chain :with_charset do |charset|
    @charset = charset
  end

  match do |response|
    _, content, charset = *content_type_header.match(CONTENT_HEADER_MATCHER).to_a

    if @charset
      @charset == charset && content == content_type
    else
      content == content_type
    end
  end

  failure_message_for_should do |response|
    if @charset
      "Content type #{content_type_header.inspect} should match #{content_type.inspect} with charset #{@charset}"
    else
      "Content type #{content_type_header.inspect} should match #{content_type.inspect}"
    end
  end

  failure_message_for_should_not do |model|
    if @charset
      "Content type #{content_type_header.inspect} should not match #{content_type.inspect} with charset #{@charset}"
    else
      "Content type #{content_type_header.inspect} should not match #{content_type.inspect}"
    end
  end

  def content_type_header
    response.headers['Content-Type']
  end
end

Answer 6

JSON comparison solution

Yields a clean but potentially large Diff:

actual = JSON.parse(response.body, symbolize_names: true)
expected = { foo: "bar" }
expect(actual).to eq expected

Example of console output from real data:

expected: {:story=>{:id=>1, :name=>"The Shire"}}
     got: {:story=>{:id=>1, :name=>"The Shire", :description=>nil, :body=>nil, :number=>1}}

   (compared using ==)

   Diff:
   @@ -1,2 +1,2 @@
   -:story => {:id=>1, :name=>"The Shire"},
   +:story => {:id=>1, :name=>"The Shire", :description=>nil, ...}

(Thanks to comment by @floatingrock)

String comparison solution

If you want an iron-clad solution, you should avoid using parsers which could introduce false positive equality; compare the response body against a string. e.g:

actual = response.body
expected = ({ foo: "bar" }).to_json
expect(actual).to eq expected

But this second solution is less visually friendly as it uses serialized JSON which would include lots of escaped quotation marks.

Custom matcher solution

I tend to write myself a custom matcher that does a much better job of pinpointing at exactly which recursive slot the JSON paths differ. Add the following to your rspec macros:

def expect_response(actual, expected_status, expected_body = nil)
  expect(response).to have_http_status(expected_status)
  if expected_body
    body = JSON.parse(actual.body, symbolize_names: true)
    expect_json_eq(body, expected_body)
  end
end

def expect_json_eq(actual, expected, path = "")
  expect(actual.class).to eq(expected.class), "Type mismatch at path: #{path}"
  if expected.class == Hash
    expect(actual.keys).to match_array(expected.keys), "Keys mismatch at path: #{path}"
    expected.keys.each do |key|
      expect_json_eq(actual[key], expected[key], "#{path}/:#{key}")
    end
  elsif expected.class == Array
    expected.each_with_index do |e, index|
      expect_json_eq(actual[index], expected[index], "#{path}[#{index}]")
    end
  else
    expect(actual).to eq(expected), "Type #{expected.class} expected #{expected.inspect} but got #{actual.inspect} at path: #{path}"
  end
end

Example of usage 1:

expect_response(response, :no_content)

Example of usage 2:

expect_response(response, :ok, {
  story: {
    id: 1,
    name: "Shire Burning",
    revisions: [ ... ],
  }
})

Example output:

Type String expected "Shire Burning" but got "Shire Burnin" at path: /:story/:name

Another example output to demonstrate a mismatch deep in a nested array:

Type Integer expected 2 but got 1 at path: /:story/:revisions[0]/:version

As you can see, the output tells you EXACTLY where to fix your expected JSON.