1 files changed, 50 insertions, 1 deletions
diff --git a/spec/models/concerns/from_set_operator_spec.rb b/spec/models/concerns/from_set_operator_spec.rb
index 8ebbb5550c9..1ef0d1adb08 100644
--- a/spec/models/concerns/from_set_operator_spec.rb
+++ b/spec/models/concerns/from_set_operator_spec.rb
@@ -3,7 +3,22 @@
 require 'spec_helper'
 
 RSpec.describe FromSetOperator do
-  describe 'when set operator method already exists' do
+  let_it_be(:from_set_operator) do
+    Class.new do
+      extend FromSetOperator
+      define_set_operator Gitlab::SQL::Union
+
+      def table_name
+        'groups'
+      end
+
+      def from(*args)
+        ''
+      end
+    end
+  end
+
+  context 'when set operator method already exists' do
     let(:redefine_method) do
       Class.new do
         def self.from_union
@@ -17,4 +32,38 @@ RSpec.describe FromSetOperator do
 
     it { expect { redefine_method }.to raise_exception(RuntimeError) }
   end
+
+  context 'with members' do
+    let_it_be(:group1) { create :group }
+    let_it_be(:group2) { create :group }
+    let_it_be(:groups) do
+      [
+        Group.where(id: group1),
+        Group.where(id: group2)
+      ]
+    end
+
+    shared_examples 'set operator called with correct members' do
+      it do
+        expect(Gitlab::SQL::Union).to receive(:new).with(groups, anything).and_call_original
+        subject
+      end
+    end
+
+    context 'as array' do
+      subject { from_set_operator.new.from_union(groups) }
+
+      it_behaves_like 'set operator called with correct members'
+
+      it { expect { subject }.not_to make_queries }
+    end
+
+    context 'as multiple parameters' do
+      subject { from_set_operator.new.from_union(*groups) }
+
+      it_behaves_like 'set operator called with correct members'
+
+      it { expect { subject }.not_to make_queries }
+    end
+  end
 end