mastodon/spec/controllers/api/media_controller_spec.rb

require 'rails_helper'

RSpec.describe Api::MediaController, type: :controller do
  render_views

  let(:user)  { Fabricate(:user, account: Fabricate(:account, username: 'alice')) }
  let(:token) { double acceptable?: true, resource_owner_id: user.id }

  before do
    allow(controller).to receive(:doorkeeper_token) { token }
  end

  describe 'POST #create' do
    before do
      post :create, params: { file: fixture_file_upload('files/attachment.jpg', 'image/jpeg') }
    end

    it 'returns http success' do
      expect(response).to have_http_status(:success)
    end

    it 'creates a media attachment' do
      expect(MediaAttachment.first).to_not be_nil
    end

    it 'uploads a file' do
      expect(MediaAttachment.first).to have_attached_file(:file)
    end

    it 'returns media ID in JSON' do
      expect(body_as_json[:id]).to eq MediaAttachment.first.id
    end
  end
end