1 files changed, 40 insertions, 0 deletions
diff --git a/spec/models/concerns/from_union_spec.rb b/spec/models/concerns/from_union_spec.rb
new file mode 100644
index 00000000000..ee427a667c6
--- /dev/null
+++ b/spec/models/concerns/from_union_spec.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe FromUnion do
+  describe '.from_union' do
+    let(:model) do
+      Class.new(ActiveRecord::Base) do
+        self.table_name = 'users'
+
+        include FromUnion
+      end
+    end
+
+    it 'selects from the results of the UNION' do
+      query = model.from_union([model.where(id: 1), model.where(id: 2)])
+
+      expect(query.to_sql).to match(/FROM \(SELECT.+UNION.+SELECT.+\) users/m)
+    end
+
+    it 'supports the use of a custom alias for the sub query' do
+      query = model.from_union(
+        [model.where(id: 1), model.where(id: 2)],
+        alias_as: 'kittens'
+      )
+
+      expect(query.to_sql).to match(/FROM \(SELECT.+UNION.+SELECT.+\) kittens/m)
+    end
+
+    it 'supports keeping duplicate rows' do
+      query = model.from_union(
+        [model.where(id: 1), model.where(id: 2)],
+        remove_duplicates: false
+      )
+
+      expect(query.to_sql)
+        .to match(/FROM \(SELECT.+UNION ALL.+SELECT.+\) users/m)
+    end
+  end
+end