1 files changed, 40 insertions, 0 deletions
diff --git a/spec/lib/gitlab/background_migration/set_merge_request_diff_files_count_spec.rb b/spec/lib/gitlab/background_migration/set_merge_request_diff_files_count_spec.rb
new file mode 100644
index 00000000000..6e9f51f510a
--- /dev/null
+++ b/spec/lib/gitlab/background_migration/set_merge_request_diff_files_count_spec.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::BackgroundMigration::SetMergeRequestDiffFilesCount, schema: 20200807152315 do
+  let(:merge_request_diff_files) { table(:merge_request_diff_files) }
+  let(:merge_request_diffs) { table(:merge_request_diffs) }
+  let(:merge_requests) { table(:merge_requests) }
+  let(:namespaces) { table(:namespaces) }
+  let(:projects) { table(:projects) }
+
+  let(:namespace) { namespaces.create!(name: 'foo', path: 'foo') }
+  let(:project) { projects.create!(namespace_id: namespace.id) }
+  let(:merge_request) { merge_requests.create!(source_branch: 'x', target_branch: 'master', target_project_id: project.id) }
+
+  it 'fills the files_count column' do
+    empty_diff = merge_request_diffs.create!(merge_request_id: merge_request.id)
+    filled_diff = merge_request_diffs.create!(merge_request_id: merge_request.id)
+
+    3.times do |n|
+      merge_request_diff_files.create!(
+        merge_request_diff_id: filled_diff.id,
+        relative_order: n,
+        new_file: false,
+        renamed_file: false,
+        deleted_file: false,
+        too_large: false,
+        a_mode: '',
+        b_mode: '',
+        old_path: '',
+        new_path: ''
+      )
+    end
+
+    described_class.new.perform(empty_diff.id, filled_diff.id)
+
+    expect(empty_diff.reload.files_count).to eq(0)
+    expect(filled_diff.reload.files_count).to eq(3)
+  end
+end