referential_spec: Move lock tests to a new file, small improvements

* Move these two tests to a new file to isolate them from the normal
  Referential model tests
* Move the `workbench` to a `let`
* Remove unnecessary schema deletions in transactional synchronous test
* Add comments describing the lock mechanism and how we test it with
  threads & sleeps

1 files changed, 80 insertions, 0 deletions

diff --git a/spec/models/referential/referential_lock_during_creation_spec.rb b/spec/models/referential/referential_lock_during_creation_spec.rb
new file mode 100644
index 000000000..ec2471015
--- /dev/null
+++ b/spec/models/referential/referential_lock_during_creation_spec.rb
@@ -0,0 +1,80 @@
+RSpec.describe Referential, type: :model do
+  
+  context "when two identical Referentials are created, only one is saved" do
+    let( :workbench ){ create :workbench }
+
+    it "works synchronously" do
+        referential_1 = build(
+          :referential,
+          workbench: workbench,
+          organisation: workbench.organisation
+        )
+        referential_2 = referential_1.dup
+        referential_2.slug = "#{referential_1.slug}_different"
+
+        metadata_1 = build(:referential_metadata)
+        metadata_2 = metadata_1.dup
+
+        referential_1.metadatas << metadata_1
+        referential_2.metadatas << metadata_2
+
+        referential_1.save
+        referential_2.save
+
+        expect(referential_1).to be_persisted
+        expect(referential_2).not_to be_persisted
+    end
+
+    it "works asynchronously", truncation: true do
+      begin
+        referential_1 = build(
+          :referential,
+          workbench: workbench,
+          organisation: workbench.organisation
+        )
+        referential_2 = referential_1.dup
+        referential_2.slug = "#{referential_1.slug}_different"
+        referential_3 = nil
+
+        metadata_1 = build(:referential_metadata)
+        metadata_2 = metadata_1.dup
+
+        referential_1.metadatas << metadata_1
+        referential_2.metadatas << metadata_2
+
+        thread_1 = Thread.new do
+          ActiveRecord::Base.transaction do
+            # seize LOCK
+            referential_1.save
+            sleep 10
+            # release LOCK
+          end
+        end
+
+        thread_2 = Thread.new do
+          sleep 5
+          ActiveRecord::Base.transaction do
+            # waits for LOCK, (because of sleep 5)
+            referential_2.save
+            # when lock was eventually obtained validation failed
+            referential_3 = create(:referential)
+          end
+        end
+
+        thread_1.join
+        thread_2.join
+
+        expect(referential_1).to be_persisted
+        expect(referential_2).not_to be_persisted
+        expect(referential_3).to be_persisted
+      ensure
+        Apartment::Tenant.drop(referential_1.slug) if referential_1.persisted?
+        Apartment::Tenant.drop(referential_2.slug) if referential_2.persisted?
+
+        if referential_3.try(:persisted?)
+          Apartment::Tenant.drop(referential_3.slug)
+        end
+      end
+    end
+  end
+end