diff --git a/spec/unit/concept_spec.rb b/spec/unit/concept_spec.rb
index 5fac74f..c963744 100644
--- a/spec/unit/concept_spec.rb
+++ b/spec/unit/concept_spec.rb
@@ -38,6 +38,22 @@
         .not_to raise_error
     end
 
+    it "generates a uuid if not given" do
+      concept = described_class.new(attrs)
+      uuid = Glossarist::Utilities::UUID.uuid_v5(
+        Glossarist::Utilities::UUID::OID_NAMESPACE,
+        concept.to_h.to_s
+      )
+
+      expect(concept.uuid).to eq(uuid)
+    end
+
+    it "assign a uuid if given" do
+      concept = described_class.new(attrs.merge("uuid" => "abc"))
+
+      expect(concept.uuid).to eq("abc")
+    end
+
     it "accepts a hash of attributes and create a concept" do
       related = [
         {
diff --git a/spec/unit/managed_concept_collection_spec.rb b/spec/unit/managed_concept_collection_spec.rb
index 14bcc3a..a5f36bb 100644
--- a/spec/unit/managed_concept_collection_spec.rb
+++ b/spec/unit/managed_concept_collection_spec.rb
@@ -57,8 +57,16 @@
   end
 
   describe "#[]" do
-    it "returns a managed concept" do
-      managed_concept = Glossarist::ManagedConcept.new("data" => { id: "id" })
+    let(:managed_concept) { Glossarist::ManagedConcept.new("data" => { id: "id" }) }
+
+    it "returns a managed concept by uuid" do
+      managed_concept_collection.store(managed_concept)
+      uuid = Glossarist::Utilities::UUID.uuid_v5(Glossarist::Utilities::UUID::OID_NAMESPACE, managed_concept.to_h.to_s)
+
+      expect(managed_concept_collection[uuid]).to eq(managed_concept)
+    end
+
+    it "returns a managed concept by id" do
       managed_concept_collection.store(managed_concept)
 
       expect(managed_concept_collection["id"]).to eq(managed_concept)