1 files changed, 42 insertions, 0 deletions
diff --git a/spec/support/shared_examples/models/concerns/from_set_operator_shared_examples.rb b/spec/support/shared_examples/models/concerns/from_set_operator_shared_examples.rb
new file mode 100644
index 00000000000..6b208c0024d
--- /dev/null
+++ b/spec/support/shared_examples/models/concerns/from_set_operator_shared_examples.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+RSpec.shared_examples 'from set operator' do |sql_klass|
+  from_set_operator_concern = described_class
+  operator_keyword = sql_klass.operator_keyword
+  operator_method = "from_#{sql_klass.operator_keyword.downcase}"
+
+  describe "##{operator_method}" do
+    let(:model) do
+      Class.new(ActiveRecord::Base) do
+        self.table_name = 'users'
+
+        include from_set_operator_concern
+      end
+    end
+
+    it "selects from the results of the #{operator_keyword}" do
+      query = model.public_send(operator_method, [model.where(id: 1), model.where(id: 2)])
+
+      expect(query.to_sql).to match(/FROM \(\(SELECT.+\)\n#{operator_keyword}\n\(SELECT.+\)\) users/m)
+    end
+
+    it 'supports the use of a custom alias for the sub query' do
+      query = model.public_send(operator_method,
+        [model.where(id: 1), model.where(id: 2)],
+        alias_as: 'kittens'
+      )
+
+      expect(query.to_sql).to match(/FROM \(\(SELECT.+\)\n#{operator_keyword}\n\(SELECT.+\)\) kittens/m)
+    end
+
+    it 'supports keeping duplicate rows' do
+      query = model.public_send(operator_method,
+        [model.where(id: 1), model.where(id: 2)],
+        remove_duplicates: false
+      )
+
+      expect(query.to_sql)
+        .to match(/FROM \(\(SELECT.+\)\n#{operator_keyword} ALL\n\(SELECT.+\)\) users/m)
+    end
+  end
+end