1 files changed, 40 insertions, 0 deletions
diff --git a/spec/migrations/ensure_filled_external_diff_store_on_merge_request_diffs_spec.rb b/spec/migrations/ensure_filled_external_diff_store_on_merge_request_diffs_spec.rb
new file mode 100644
index 00000000000..808580d5770
--- /dev/null
+++ b/spec/migrations/ensure_filled_external_diff_store_on_merge_request_diffs_spec.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20200910170908_ensure_filled_external_diff_store_on_merge_request_diffs.rb')
+
+RSpec.describe EnsureFilledExternalDiffStoreOnMergeRequestDiffs, schema: 20200908095446 do
+  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) }
+
+  before do
+    constraint_name = 'check_93ee616ac9'
+
+    # In order to insert a row with a NULL to fill.
+    ActiveRecord::Base.connection.execute "ALTER TABLE merge_request_diffs DROP CONSTRAINT #{constraint_name}"
+
+    @external_diff_store_1 = merge_request_diffs.create!(external_diff_store: 1, merge_request_id: merge_request.id)
+    @external_diff_store_2 = merge_request_diffs.create!(external_diff_store: 2, merge_request_id: merge_request.id)
+    @external_diff_store_nil = merge_request_diffs.create!(external_diff_store: nil, merge_request_id: merge_request.id)
+
+    # revert DB structure
+    ActiveRecord::Base.connection.execute "ALTER TABLE merge_request_diffs ADD CONSTRAINT #{constraint_name} CHECK ((external_diff_store IS NOT NULL)) NOT VALID"
+  end
+
+  it 'correctly migrates nil external_diff_store to 1' do
+    migrate!
+
+    @external_diff_store_1.reload
+    @external_diff_store_2.reload
+    @external_diff_store_nil.reload
+
+    expect(@external_diff_store_1.external_diff_store).to eq(1)   # unchanged
+    expect(@external_diff_store_2.external_diff_store).to eq(2)   # unchanged
+    expect(@external_diff_store_nil.external_diff_store).to eq(1) # nil => 1
+  end
+end