add test coverage for VersionInfo

related to sparklemotion#1896

test/test_version.rb

@@ -0,0 +1,58 @@
+require "helper"
+require "rbconfig"
+require "json"
+
+module TestVersionInfoTests
+  #
+  #  This module is mixed into test classes below so that the tests
+  #  are validated when `nokogiri.rb` is required and when
+  #  `nokogiri/version.rb` is required. See #1896 for background.
+  #
+  def test_version_info_for_xerces
+    skip "xerces is only used for JRuby" unless Nokogiri.jruby?
+    assert_equal @version_info["xerces"], Nokogiri::VERSION_INFO["xerces"]
+  end
+
+  def test_version_info_for_nekohtml
+    skip "nekohtml is only used for JRuby" unless Nokogiri.jruby?
+    assert_equal @version_info["nekohtml"], Nokogiri::VERSION_INFO["nekohtml"]
+  end
+
+  def test_version_info_for_libxml
+    skip "libxml2 is only used for CRuby" unless Nokogiri.uses_libxml?
+    assert_equal @version_info["libxml"]["compiled"], Nokogiri::LIBXML_VERSION
+  end
+end
+
+class TestVersionInfo
+  RUBYEXEC = File.join(RbConfig::CONFIG["bindir"], RbConfig::CONFIG["RUBY_INSTALL_NAME"])
+  ROOTDIR = File.expand_path(File.join(File.dirname(__FILE__), ".."))
+
+  class Base < Nokogiri::TestCase
+    def setup
+      super
+      version_info = Dir.chdir(ROOTDIR) do
+        `#{RUBYEXEC} -Ilib -rjson -r#{@require_me} -e 'puts Nokogiri::VERSION_INFO.to_json'`
+      end
+      @version_info = JSON.parse version_info
+    end
+  end
+
+  class RequireNokogiri < TestVersionInfo::Base
+    include TestVersionInfoTests
+
+    def setup
+      @require_me = "nokogiri"
+      super
+    end
+  end
+
+  class RequireVersionFileOnly < TestVersionInfo::Base
+    include TestVersionInfoTests
+
+    def setup
+      @require_me = "nokogiri/version"
+      super
+    end
+  end
+end