1 files changed, 51 insertions, 0 deletions
diff --git a/spec/lib/api/helpers/common_helpers_spec.rb b/spec/lib/api/helpers/common_helpers_spec.rb
new file mode 100644
index 00000000000..5162d2f1000
--- /dev/null
+++ b/spec/lib/api/helpers/common_helpers_spec.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe API::Helpers::CommonHelpers do
+  include Rack::Test::Methods
+
+  subject do
+    Class.new(Grape::API) do
+      helpers API::Helpers::CommonHelpers
+
+      before do
+        coerce_nil_params_to_array!
+      end
+
+      params do
+        requires :id, type: String
+        optional :array, type: Array, coerce_with: ::API::Validations::Types::CommaSeparatedToArray.coerce
+        optional :array_of_strings, type: Array[String], coerce_with: ::API::Validations::Types::CommaSeparatedToArray.coerce
+        optional :array_of_ints, type: Array[Integer], coerce_with: ::API::Validations::Types::CommaSeparatedToIntegerArray.coerce
+      end
+      get ":id" do
+        params.to_json
+      end
+    end
+  end
+
+  def app
+    subject
+  end
+
+  describe '.coerce_nil_params_to_array!' do
+    let(:json_response) { Gitlab::Json.parse(last_response.body) }
+
+    it 'converts all nil parameters to empty arrays' do
+      get '/test?array=&array_of_strings=&array_of_ints='
+
+      expect(json_response['array']).to eq([])
+      expect(json_response['array_of_strings']).to eq([])
+      expect(json_response['array_of_ints']).to eq([])
+    end
+
+    it 'leaves non-nil parameters alone' do
+      get '/test?array=&array_of_strings=test,me&array_of_ints=1,2'
+
+      expect(json_response['array']).to eq([])
+      expect(json_response['array_of_strings']).to eq(%w(test me))
+      expect(json_response['array_of_ints']).to eq([1, 2])
+    end
+  end
+end