练习要求为所提供的每个功能编写单元测试.我正在测试的一个项目是,是否引发了适当的异常.建议我们使用assert_raise来实现此目的.

这是我正在测试的代码：

class ParserError < Exception

end

Pair = Struct.new(:token,:word)

def peek(word_list)
    begin
        word_list.first.token
    rescue
        nil
    end 
end

def match(word_list,expecting)
    word = word_list.shift
    if word.token == expecting
        word
    else
        nil
    end
end

def skip_word(word_list,token)
    while peek(word_list) == token
        match(word_list,token)
    end
end

def parse_verb(word_list)
    skip_word(word_list,:stop)

    if peek(word_list) == :verb
        return match(word_list,:verb)
    else
        raise ParserError.new("Expected a verb next.")
    end
end

这是测试,对于函数parse_verb：

def test_parse_verb
    list_one = [Pair.new(:verb,'go'),Pair.new(:noun,'king')]
    assert_equal(parse_verb(list_one),Pair.new(:verb,'go'))

    list_two = [Pair.new(:noun,'player'),'king')]
    assert_raise(ParserError.new("Expected a verb next.")) {parse_verb(list_two)}
end

当我运行测试时,它失败了,这是我得到的消息：

Larson-2:test larson$ruby test_sentence.rb
Loaded suite test_sentence
Started
.F..
Finished in 0.001204 seconds.

  1) Failure:
test_parse_verb(SentenceTests) [test_sentence.rb:36]:
[#<ParserError: Expected a noun or direction next.>] exception expected,not
Class: <ParserError>
Message: <"Expected a verb next.">
---Backtrace---
/Users/larson/Ruby/projects/ex48/lib/sentence.rb:45:in `parse_verb'
test_sentence.rb:36:in `block in test_parse_verb'
---------------

4 tests,7 assertions,1 failures,0 errors,0 skips

Test run options: --seed 40627

基于我对assert_raise函数的理解,这个测试应该通过,我使用它的方式有什么问题吗？

如果有人想要我正在使用的所有文件的完整源代码,我可以使用here