Fix JenkinsService test button

Closes #637

CHANGELOG-EE

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.9.0 (unreleased)
+  - Fix JenkinsService test button
   - Fix nil user handling in UpdateMirrorService
   - Allow LDAP to mark users as external based on their group membership. !432
   - Forbid MR authors from approving their own MRs

app/models/project_services/jenkins_service.rb

@@ -53,14 +53,13 @@ class JenkinsService < CiService
 
   def test(data)
     begin
-      result = execute(data)
-      message = result.message || result unless result.nil?
-      return { success: false, result: message } if result.code != 200
+      code, message = execute(data)
+      return { success: false, result: message } if code != 200
     rescue StandardError => error
       return { success: false, result: error }
     end
 
-    { success: true, result: result }
+    { success: true, result: message }
   end
 
   def auth

spec/models/project_services/jenkins_service_spec.rb

@@ -25,6 +25,16 @@ describe JenkinsService do
     it { is_expected.to have_one :service_hook }
   end
   let(:project) { create(:project) }
+  let(:jenkins_params) do
+    {
+      active: true,
+      project: project,
+      properties: {
+        jenkins_url: 'http://jenkins.example.com/',
+        project_name: 'my_project'
+      }
+    }
+  end
 
   describe 'username validation' do
     before do
@@ -74,19 +84,26 @@ describe JenkinsService do
     end
   end
 
+  describe '#test' do
+    it 'returns the right status' do
+      user = create(:user, username: 'username')
+      project = create(:project, name: 'project')
+      push_sample_data = Gitlab::PushDataBuilder.build_sample(project, user)
+      jenkins_service = described_class.create(jenkins_params)
+      stub_request(:post, jenkins_service.hook_url)
+
+      result = jenkins_service.test(push_sample_data)
+
+      expect(result).to eq({ success: true, result: '' })
+    end
+  end
+
   describe '#execute' do
     it 'adds default web hook headers to the request' do
       user = create(:user, username: 'username')
       project = create(:project, name: 'project')
       push_sample_data = Gitlab::PushDataBuilder.build_sample(project, user)
-      jenkins_service = described_class.create(
-        active: true,
-        project: project,
-        properties: {
-          jenkins_url: 'http://jenkins.example.com/',
-          project_name: 'my_project'
-        }
-      )
+      jenkins_service = described_class.create(jenkins_params)
       stub_request(:post, jenkins_service.hook_url)
 
       jenkins_service.execute(push_sample_data)