add class to wrap sensitive values

spec/sensitive_spec.rb

@@ -0,0 +1,26 @@
+require "minitest/autorun"
+
+$LOAD_PATH.unshift File.dirname(__FILE__) + "/../lib"
+
+require "sensitive"
+
+ALPHABET = ('a' .. 'z').reduce(:concat)
+
+describe "Sensitive" do
+  before do
+    @s = Sensitive.new ALPHABET
+  end
+
+  it "test initialize" do
+    _(@s.to_s).must_equal "ab" + "*" * 22 + "yz"
+  end
+
+  it "test initialize" do
+    _(@s.unwrap).must_equal ALPHABET
+  end
+
+  it "test using different mask character" do
+    s = Sensitive.new ALPHABET, ch: "x" 
+    _(s.to_s).must_equal "x"
+  end
+end