Add coverage for LanguageValidator (#25593)

spec/validators/language_validator_spec.rb

@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe LanguageValidator do
+  let(:record_class) do
+    Class.new do
+      include ActiveModel::Validations
+      attr_accessor :locale
+
+      validates :locale, language: true
+    end
+  end
+  let(:record) { record_class.new }
+
+  describe '#validate_each' do
+    context 'with a nil value' do
+      it 'does not add errors' do
+        record.locale = nil
+
+        expect(record).to be_valid
+        expect(record.errors).to be_empty
+      end
+    end
+
+    context 'with an array of values' do
+      it 'does not add errors with array of existing locales' do
+        record.locale = %w(en fr)
+
+        expect(record).to be_valid
+        expect(record.errors).to be_empty
+      end
+
+      it 'adds errors with array having some non-existing locales' do
+        record.locale = %w(en fr missing)
+
+        expect(record).to_not be_valid
+        expect(record.errors.first.attribute).to eq(:locale)
+        expect(record.errors.first.type).to eq(:invalid)
+      end
+    end
+
+    context 'with a locale string' do
+      it 'does not add errors when string is an existing locale' do
+        record.locale = 'en'
+
+        expect(record).to be_valid
+        expect(record.errors).to be_empty
+      end
+
+      it 'adds errors when string is non-existing locale' do
+        record.locale = 'missing'
+
+        expect(record).to_not be_valid
+        expect(record.errors.first.attribute).to eq(:locale)
+        expect(record.errors.first.type).to eq(:invalid)
+      end
+    end
+  end
+end