diff --git a/app/models/synapse.rb b/app/models/synapse.rb
index 0b40da02..ea5889cc 100644
--- a/app/models/synapse.rb
+++ b/app/models/synapse.rb
@@ -1,5 +1,4 @@
 class Synapse < ActiveRecord::Base
-
   belongs_to :user
 
   belongs_to :topic1, :class_name => "Topic", :foreign_key => "node1_id"
@@ -13,15 +12,17 @@ class Synapse < ActiveRecord::Base
   validates :permission, presence: true
   validates :permission, inclusion: { in: Perm::ISSIONS.map(&:to_s) }
 
+  validates :category, inclusion: { in: ['from-to', 'both'], allow_nil: true }
+
   # :nocov:
   def user_name
-    self.user.name
+    user.name
   end
   # :nocov:
 
   # :nocov:
   def user_image
-    self.user.image.url
+    user.image.url
   end
   # :nocov:
 
diff --git a/spec/controllers/synapses_controller_spec.rb b/spec/controllers/synapses_controller_spec.rb
index 9b7471ab..478ee6ed 100644
--- a/spec/controllers/synapses_controller_spec.rb
+++ b/spec/controllers/synapses_controller_spec.rb
@@ -2,15 +2,15 @@ require 'rails_helper'
 
 RSpec.describe SynapsesController, type: :controller do
   let(:synapse) { create(:synapse) }
-  let(:valid_attributes) { synapse.attributes.except(:id) }
-  let(:invalid_attributes) { { permission: :commons } } 
+  let(:valid_attributes) { synapse.attributes.except('id') }
+  let(:invalid_attributes) { { permission: :invalid_lol } } 
   before :each do
     sign_in
   end
 
   describe 'GET #show' do
     it 'assigns the requested synapse as @synapse' do
-      get :show, { id: synapse.to_param }
+      get :show, { id: synapse.to_param, format: :json }
       expect(assigns(:synapse)).to eq(synapse)
     end
   end
@@ -18,27 +18,28 @@ RSpec.describe SynapsesController, type: :controller do
   describe 'POST #create' do
     context 'with valid params' do
       it 'creates a new Synapse' do
+        synapse.reload # ensure it's present
         expect do
-          post :create, { synapse: valid_attributes }
+          post :create, { synapse: valid_attributes, format: :json }
         end.to change(Synapse, :count).by(1)
       end
 
       it 'assigns a newly created synapse as @synapse' do
-        post :create, { synapse: valid_attributes }
+        post :create, { synapse: valid_attributes, format: :json }
         expect(assigns(:synapse)).to be_a(Synapse)
         expect(assigns(:synapse)).to be_persisted
       end
 
-      it 'redirects to the created synapse' do
-        post :create, { synapse: valid_attributes }
-        expect(response).to redirect_to(Synapse.last)
+      it 'returns 201 CREATED' do
+        post :create, { synapse: valid_attributes, format: :json }
+        expect(response.status).to eq 201
       end
     end
 
     context 'with invalid params' do
-      it 'assigns a newly created but unsaved synapse as @synapse' do
-        post :create, { synapse: invalid_attributes }
-        expect(assigns(:synapse)).to be_a_new(Synapse)
+      it 'returns 422 UNPROCESSABLE ENTITY' do
+        post :create, { synapse: invalid_attributes, format: :json }
+        expect(response.status).to eq 422
       end
     end
   end
@@ -46,48 +47,49 @@ RSpec.describe SynapsesController, type: :controller do
   describe 'PUT #update' do
     context 'with valid params' do
       let(:new_attributes) do
-        skip('Add a hash of attributes valid for your model')
+        { desc: 'My new description',
+          category: 'both',
+          permission: :public }
       end
 
       it 'updates the requested synapse' do
         put :update,
-            { id: synapse.to_param, synapse: new_attributes }
+            { id: synapse.to_param, synapse: new_attributes, format: :json }
         synapse.reload
-        skip('Add assertions for updated state')
+        expect(synapse.desc).to eq 'My new description'
+        expect(synapse.category).to eq 'both'
+        expect(synapse.permission).to eq 'public'
       end
 
-      it 'assigns the requested synapse as @synapse' do
+      it 'returns 204 NO CONTENT' do 
         put :update,
-            { id: synapse.to_param, synapse: valid_attributes }
-        expect(assigns(:synapse)).to eq(synapse)
-      end
-
-      it 'redirects to the synapse' do
-        put :update,
-            { id: synapse.to_param, synapse: valid_attributes }
-        expect(response).to redirect_to(synapse)
+            { id: synapse.to_param, synapse: valid_attributes, format: :json }
+        expect(response.status).to eq 204
       end
     end
 
     context 'with invalid params' do
       it 'assigns the synapse as @synapse' do
         put :update,
-            { id: synapse.to_param, synapse: invalid_attributes }
+            { id: synapse.to_param, synapse: invalid_attributes, format: :json }
         expect(assigns(:synapse)).to eq(synapse)
       end
     end
   end
 
   describe 'DELETE #destroy' do
+    let(:synapse) { create(:synapse, user: controller.current_user) }
+
     it 'destroys the requested synapse' do
+      synapse.reload # ensure it's present
       expect do
-        delete :destroy, { id: synapse.to_param }
+        delete :destroy, { id: synapse.to_param, format: :json }
       end.to change(Synapse, :count).by(-1)
     end
 
-    it 'redirects to the synapses list' do
-      delete :destroy, { id: synapse.to_param }
-      expect(response).to redirect_to(synapses_url)
+    it 'returns 204 NO CONTENT' do
+      delete :destroy, { id: synapse.to_param, format: :json }
+      expect(response.status).to eq 204
     end
   end
 end
diff --git a/spec/factories/synapses.rb b/spec/factories/synapses.rb
index b83a0073..4454a7a4 100644
--- a/spec/factories/synapses.rb
+++ b/spec/factories/synapses.rb
@@ -1,9 +1,10 @@
 FactoryGirl.define do
   factory :synapse do
     sequence(:desc) { |n| "Cool synapse ##{n}" }
-    category :to
+    category :'from-to'
     permission :commons
     association :topic1, factory: :topic
     association :topic2, factory: :topic
+    user
   end
 end
diff --git a/spec/models/synapse_spec.rb b/spec/models/synapse_spec.rb
index a1069805..dcf85358 100644
--- a/spec/models/synapse_spec.rb
+++ b/spec/models/synapse_spec.rb
@@ -8,6 +8,7 @@ RSpec.describe Synapse, type: :model do
   it { is_expected.to have_many :mappings }
   it { is_expected.to validate_presence_of :permission }
   it { is_expected.to validate_inclusion_of(:permission).in_array Perm::ISSIONS.map(&:to_s) }
+  it { is_expected.to validate_inclusion_of(:category).in_array ['from-to', 'both'] }
   it { is_expected.to validate_length_of(:desc).is_at_least(0) } # TODO don't allow nil
 
   context 'permissions' do