```ruby
require 'spec_helper.rb'

module RbNFA
  describe Regexp do
    it "can be build from literal string" do 
      regexp = Regexp.new("a")
      regexp.should_not be_nil
    end
    
    it "can math string" do
      pending("to implementig other")
      regexp = Regexp.new("a")
      regexp.match("aaa").should be_true
    end

    it "cannot match incorrect string" do
      pending("implementing other")
      regexp = Regexp.new("a")
      regexp.match("bbb").should be_false
    end
  end

  describe Lexer do
    let(:lexer){ Lexer.new }
        
    it "on empty string don't generate tokens" do
      lexer.lex("").should have(0).tokens
    end

    it "on literal chracter generate literal token" do 
      result = lexer.lex("a")
      result.should have(1).token
      result[0].should be_kind_of LiteralToken
    end

    it "on plus generate one or more token" do 
      result = lexer.lex("+")
      result.should have(1).token
      result.first.should be OneOrMoreToken
    end

    it "on star generate zero or more token" do
      result = lexer.lex("*")
      result.should have(1).token
      result.first.should be ZeroOrMoreToken
    end
      

    it "on question mark generate zero or one token"

    it "on left parenthesie generate begin group token"

    it "on right parenthiesie generate end group token"

  end
end

```

Add test for zero or one token
user
```ruby
require 'spec_helper.rb'

module RbNFA
  describe Regexp do
    it "can be build from literal string" do 
      regexp = Regexp.new("a")
      regexp.should_not be_nil
    end
    
    it "can math string" do
      pending("to implementig other")
      regexp = Regexp.new("a")
      regexp.match("aaa").should be_true
    end

    it "cannot match incorrect string" do
      pending("implementing other")
      regexp = Regexp.new("a")
      regexp.match("bbb").should be_false
    end
  end

  describe Lexer do
    let(:lexer){ Lexer.new }
        
    it "on empty string don't generate tokens" do
      lexer.lex("").should have(0).tokens
    end

    it "on literal chracter generate literal token" do 
      result = lexer.lex("a")
      result.should have(1).token
      result[0].should be_kind_of LiteralToken
    end

    it "on plus generate one or more token" do 
      result = lexer.lex("+")
      result.should have(1).token
      result.first.should be OneOrMoreToken
    end

    it "on star generate zero or more token" do
      result = lexer.lex("*")
      result.should have(1).token
      result.first.should be ZeroOrMoreToken
    end
      

    it "on question mark generate zero or one token" do
      result = lexer.lex("?")
      result.should have(1).token
      result.first.should be ZeroOrOneToken
    end

    it "on left parenthesie generate begin group token"

    it "on right parenthiesie generate end group token"

  end
end

```
assistant