Boy Scout: Create document parser spec file

Regroup DocumentParser spec. Now they're duplicates in
local_census_specs and census_api_spec.

Move duplicate private method "dni?(document_type) from
LocalCensus and CensusAPI to DocumentParser

spec/lib/document_parser_spec.rb

@@ -0,0 +1,30 @@
+require "rails_helper"
+include DocumentParser
+
+describe DocumentParser do
+
+  describe "#get_document_number_variants" do
+    it "trims and cleans up entry" do
+      expect(DocumentParser.get_document_number_variants(2, "  1 2@ 34")).to eq(["1234"])
+    end
+
+    it "returns only one try for passports & residence cards" do
+      expect(DocumentParser.get_document_number_variants(2, "1234")).to eq(["1234"])
+      expect(DocumentParser.get_document_number_variants(3, "1234")).to eq(["1234"])
+    end
+
+    it "takes only the last 8 digits for dnis and resicence cards" do
+      expect(DocumentParser.get_document_number_variants(1, "543212345678")).to eq(["12345678"])
+    end
+
+    it "tries all the dni variants padding with zeroes" do
+      expect(DocumentParser.get_document_number_variants(1, "0123456")).to eq(["123456", "0123456", "00123456"])
+      expect(DocumentParser.get_document_number_variants(1, "00123456")).to eq(["123456", "0123456", "00123456"])
+    end
+
+    it "adds upper and lowercase letter when the letter is present" do
+      expect(DocumentParser.get_document_number_variants(1, "1234567A")).to eq(%w(1234567 01234567 1234567a 1234567A 01234567a 01234567A))
+    end
+  end
+
+end