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

A lot of the above answers are a bit out of date, so this is a quick summary for a more recent version of RSpec (3.8+). This solution raises no warnings from rubocop-rspec and is inline with rspec best practices:

A successful JSON response is identified by two things:

1. The content type of the response is application/json
2. The body of the response can be parsed without errors

Assuming that the response object is the anonymous subject of the test, both of the above conditions can be validate using Rspec's built in matchers:

context 'when response is received' do
  subject { response }

  # check for a successful JSON response
  it { is_expected.to have_attributes(content_type: include('application/json')) }
  it { is_expected.to have_attributes(body: satisfy { |v| JSON.parse(v) }) }

  # validates OP's condition
  it { is_expected.to satisfy { |v| JSON.parse(v.body).key?('success') }
  it { is_expected.to satisfy { |v| JSON.parse(v.body)['success'] == true }
end

If you're prepared to name your subject then the above tests can be simplified further:

context 'when response is received' do
  subject(:response) { response }

  it 'responds with a valid content type' do
    expect(response.content_type).to include('application/json')
  end

  it 'responds with a valid json object' do
    expect { JSON.parse(response.body) }.not_to raise_error
  end

  it 'validates OPs condition' do
    expect(JSON.parse(response.body, symoblize_names: true))
      .to include(success: true)
  end
end