diff --git a/app/controllers/jwt_controller.rb b/app/controllers/jwt_controller.rb
index 0edf084e9e4bb1ff7e79593e5f46fd80951c9105..f5aa5397ff1c98e2e36a28f56704d703936b2c64 100644
--- a/app/controllers/jwt_controller.rb
+++ b/app/controllers/jwt_controller.rb
@@ -9,7 +9,7 @@ class JwtController < ApplicationController
 
   def auth
     service = SERVICES[params[:service]]
-    head :not_found unless service
+    return head :not_found unless service
 
     result = service.new(@project, @user, auth_params).execute
 
diff --git a/spec/requests/jwt_controller_spec.rb b/spec/requests/jwt_controller_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..7bb71365a48cc7a4162a9e6986ed68bbfa487193
--- /dev/null
+++ b/spec/requests/jwt_controller_spec.rb
@@ -0,0 +1,72 @@
+require 'spec_helper'
+
+describe JwtController do
+  let(:service) { double(execute: {}) }
+  let(:service_class) { double(new: service) }
+  let(:service_name) { 'test' }
+  let(:parameters) { { service: service_name } }
+
+  before { stub_const('JwtController::SERVICES', service_name => service_class) }
+
+  context 'existing service' do
+    subject! { get '/jwt/auth', parameters }
+
+    it { expect(response.status).to eq(200) }
+
+    context 'returning custom http code' do
+      let(:service) { double(execute: { http_status: 505 }) }
+
+      it { expect(response.status).to eq(505) }
+    end
+  end
+
+  context 'when using authorized request' do
+    context 'using CI token' do
+      let(:project) { create(:empty_project, runners_token: 'token', builds_enabled: builds_enabled) }
+      let(:headers) { { authorization: credentials('gitlab_ci_token', project.runners_token) } }
+
+      subject! { get '/jwt/auth', parameters, headers }
+
+      context 'project with enabled CI' do
+        let(:builds_enabled) { true }
+
+        it { expect(service_class).to have_received(:new).with(project, nil, parameters) }
+      end
+
+      context 'project with disabled CI' do
+        let(:builds_enabled) { false }
+
+        it { expect(response.status).to eq(403) }
+      end
+    end
+
+    context 'using User login' do
+      let(:user) { create(:user) }
+      let(:headers) { { authorization: credentials('user', 'password') } }
+
+      before { expect_any_instance_of(Gitlab::Auth).to receive(:find).with('user', 'password').and_return(user) }
+
+      subject! { get '/jwt/auth', parameters, headers }
+
+      it { expect(service_class).to have_received(:new).with(nil, user, parameters) }
+    end
+
+    context 'using invalid login' do
+      let(:headers) { { authorization: credentials('invalid', 'password') } }
+
+      subject! { get '/jwt/auth', parameters, headers }
+
+      it { expect(response.status).to eq(403) }
+    end
+  end
+
+  context 'unknown service' do
+    subject! { get '/jwt/auth', service: 'unknown' }
+
+    it { expect(response.status).to eq(404) }
+  end
+
+  def credentials(login, password)
+    ActionController::HttpAuthentication::Basic.encode_credentials(login, password)
+  end
+end