added test case for traditional encryption

zip file generated by archive-zip as reference

test/encryption_test.rb

@@ -0,0 +1,33 @@
+require 'test_helper'
+
+class EncryptionTest < MiniTest::Test
+  ENCRYPT_ZIP_TEST_FILE = 'test/data/zipWithEncryption.zip'
+  INPUT_FILE1 = 'test/data/file1.txt'
+
+  def test_encrypt
+    test_file = open(ENCRYPT_ZIP_TEST_FILE, 'rb').read
+
+    @rand = [250, 143, 107, 13, 143, 22, 155, 75, 228, 150, 12]
+    @output = ::Zip::DOSTime.stub(:now, ::Zip::DOSTime.new(2014, 12, 17, 15, 56, 24)) do
+      Random.stub(:rand, lambda { |range| @rand.shift }) do
+        Zip::OutputStream.write_buffer(::StringIO.new(''), Zip::TraditionalEncrypter.new('password')) do |zos|
+          zos.put_next_entry('file1.txt')
+          zos.write open(INPUT_FILE1).read
+        end.string
+      end
+    end
+
+    @output.unpack("C*").each_with_index do |c, i|
+      assert_equal test_file[i].ord, c
+    end
+  end
+
+  def test_decrypt
+    Zip::InputStream.open(ENCRYPT_ZIP_TEST_FILE, 0, Zip::TraditionalDecrypter.new('password')) do |zis|
+      entry = zis.get_next_entry
+      assert_equal 'file1.txt', entry.name
+      assert_equal 1327, entry.size
+      assert_equal open(INPUT_FILE1, 'r').read, zis.read
+    end
+  end
+end