Test the `staging` cycle analytics phase.

Remove overlap from the "start + end" durations in the happy test
case. For the `staging` phase, the end time is the _first_ deployment
that happens after the MR merge.

If we have 5 MRs where the `start_time`s (merge time) are the
same, and all the `end_time`s (deploy to production) a few days from
now, only the earliest deploy will get picked up, because that
consitutes a deploy for _all_ the MRs.

We fix this by removing overlap. Every `start_time` is now generated to
be _after_ the preceding `end_time`.

3 files changed, 85 insertions, 4 deletions

diff --git a/app/models/cycle_analytics/queries.rb b/app/models/cycle_analytics/queries.rb
index 7816c96a0ed..2d134a0d9a4 100644
--- a/app/models/cycle_analytics/queries.rb
+++ b/app/models/cycle_analytics/queries.rb
@@ -85,6 +85,8 @@ class CycleAnalytics
         lambda do |data_point|
           merge_request = data_point[:merge_request]
           if merge_request.metrics.present?
+            # The first production deploy to the target branch that occurs after the merge request has been merged in.
+            # TODO: Does this need to account for reverts?
             deployments = Deployment.joins(:environment).where(ref: merge_request.target_branch, "environments.name" => "production").
                           where("deployments.created_at > ?", merge_request.metrics.merged_at)
             deployment = deployments.order(:created_at).first
diff --git a/spec/models/cycle_analytics/staging_spec.rb b/spec/models/cycle_analytics/staging_spec.rb
new file mode 100644
index 00000000000..23e01532500
--- /dev/null
+++ b/spec/models/cycle_analytics/staging_spec.rb
@@ -0,0 +1,79 @@
+require 'spec_helper'
+
+describe 'CycleAnalytics#staging', feature: true do
+  let(:project) { create(:project) }
+  let(:from_date) { 10.days.ago }
+  let(:user) { create(:user, :admin) }
+  subject { CycleAnalytics.new(project, from: from_date) }
+
+  def create_merge_request_closing_issue(issue, message: nil)
+    source_branch = random_git_name
+    project.repository.add_branch(user, source_branch, 'master')
+    sha = project.repository.commit_file(user, random_git_name, "content", "commit message", source_branch, false)
+    project.repository.commit(sha)
+
+    opts = {
+      title: 'Awesome merge_request',
+      description: message || "Fixes #{issue.to_reference}",
+      source_branch: source_branch,
+      target_branch: 'master'
+    }
+
+    MergeRequests::CreateService.new(project, user, opts).execute
+  end
+
+  def merge_merge_requests_closing_issue(issue)
+    merge_requests = issue.closed_by_merge_requests
+    merge_requests.each { |merge_request| MergeRequests::MergeService.new(project, user).execute(merge_request) }
+  end
+
+  def deploy_master(environment: 'production')
+    CreateDeploymentService.new(project, user, {
+                                  environment: environment,
+                                  ref: 'master',
+                                  tag: false,
+                                  sha: project.repository.commit('master').sha
+                                }).execute
+  end
+
+  generate_cycle_analytics_spec(phase: :staging,
+                                data_fn: lambda do |context|
+                                  issue = context.create(:issue, project: context.project)
+                                  { issue: issue, merge_request: context.create_merge_request_closing_issue(issue) }
+                                end,
+                                start_time_conditions: [["merge request that closes issue is merged", -> (context, data) { context.merge_merge_requests_closing_issue(data[:issue])} ]],
+                                end_time_conditions:   [["merge request that closes issue is deployed to production", -> (context, data) { context.deploy_master }],
+                                                        ["production deploy happens after merge request is merged (along with other changes)",
+                                                         lambda do |context, data|
+                                                           # Make other changes on master
+                                                           sha = context.project.repository.commit_file(context.user, context.random_git_name, "content", "commit message", 'master', false)
+                                                           context.project.repository.commit(sha)
+
+                                                           context.deploy_master
+                                                         end]])
+
+  context "when a regular merge request (that doesn't close the issue) is merged and deployed" do
+    it "returns nil" do
+      5.times do
+        merge_request = create(:merge_request)
+        MergeRequests::MergeService.new(project, user).execute(merge_request)
+        deploy_master
+      end
+
+      expect(subject.staging).to be_nil
+    end
+  end
+
+  context "when the deployment happens to a non-production environment" do
+    it "returns nil" do
+      5.times do
+        issue = create(:issue, project: project)
+        merge_request = create_merge_request_closing_issue(issue)
+        MergeRequests::MergeService.new(project, user).execute(merge_request)
+        deploy_master(environment: 'staging')
+      end
+
+      expect(subject.staging).to be_nil
+    end
+  end
+end
diff --git a/spec/support/cycle_analytics_helpers.rb b/spec/support/cycle_analytics_helpers.rb
index b2ca42d7cce..4819f8b517a 100644
--- a/spec/support/cycle_analytics_helpers.rb
+++ b/spec/support/cycle_analytics_helpers.rb
@@ -26,10 +26,10 @@ module CycleAnalyticsHelpers
       context "start condition: #{start_time_conditions.map(&:first).to_sentence}" do
         context "end condition: #{end_time_conditions.map(&:first).to_sentence}" do
           it "finds the median of available durations between the two conditions" do
-            time_differences = Array.new(5) do
+            time_differences = Array.new(5) do |index|
               data = data_fn[self]
-              start_time = Time.now
-              end_time = rand(1..10).days.from_now
+              start_time = (index * 10).days.from_now
+              end_time = start_time + rand(1..5).days
 
               start_time_conditions.each do |condition_name, condition_fn|
                 Timecop.freeze(start_time) { condition_fn[self, data] }
@@ -43,7 +43,7 @@ module CycleAnalyticsHelpers
             end
 
             median_time_difference = time_differences.sort[2]
-            expect(subject.send(phase)).to be_within(2).of(median_time_difference)
+            expect(subject.send(phase)).to be_within(5).of(median_time_difference)
           end
 
           context "when the data belongs to another project" do