Fix MergeRequestsHelper spec

Also, there was a file called `spec/helpers/merge_requests_helper` that
was never being run because it didn't end in `_spec`. This consolidates
that file's tests into the correct spec file.

spec/helpers/merge_request_helper_spec.rb

@@ -4,7 +4,7 @@ describe MergeRequestsHelper do
   let(:project) { create :project }
   let(:merge_request) { MergeRequest.new }
   let(:ci_service) { CiService.new }
-  let(:last_commit) { Commit.new({}) }
+  let(:last_commit) { Commit.new({}, project) }
 
   before do
     merge_request.stub(:source_project) { project }
@@ -19,4 +19,25 @@ describe MergeRequestsHelper do
       expect(ci_build_details_path(merge_request)).to_not match("secret")
     end
   end
+
+  describe 'issues_sentence' do
+    subject { issues_sentence(issues) }
+    let(:issues) do
+      [build(:issue, iid: 1), build(:issue, iid: 2), build(:issue, iid: 3)]
+    end
+
+    it { is_expected.to eq('#1, #2, and #3') }
+
+    context 'for JIRA issues' do
+      let(:issues) do
+        [
+          JiraIssue.new('JIRA-123', project),
+          JiraIssue.new('JIRA-456', project),
+          JiraIssue.new('FOOBAR-7890', project)
+        ]
+      end
+
+      it { is_expected.to eq('#JIRA-123, #JIRA-456, and #FOOBAR-7890') }
+    end
+  end
 end

spec/helpers/merge_requests_helper.rb

-require 'spec_helper'
-
-describe MergeRequestsHelper do
-  describe :issues_sentence do
-    subject { issues_sentence(issues) }
-    let(:issues) do
-      [build(:issue, iid: 1), build(:issue, iid: 2), build(:issue, iid: 3)]
-    end
-
-    it { is_expected.to eq('#1, #2, and #3') }
-
-    context 'for JIRA issues' do
-      let(:issues) do
-        [JiraIssue.new('JIRA-123'), JiraIssue.new('JIRA-456'), JiraIssue.new('FOOBAR-7890')]
-      end
-
-      it { is_expected.to eq('#JIRA-123, #JIRA-456, and #FOOBAR-7890') }
-    end
-  end
-end