Ruby Rspec： expectvsexpect什么区别

在学习rspec语法时，我注意到这段代码是有效的:

  context "given a bad list of players" do
    let(:bad_players) { {} }

    it "fails to create given a bad player list" do
       expect{ Team.new("Random", bad_players) }.to raise_error
     end 
  end

但这段代码没有:

  context "given a bad list of players" do
    let(:bad_players) { {} }

    it "fails to create given a bad player list" do
       expect( Team.new("Random", bad_players) ).to raise_error
     end 
  end

这给了我一个错误:

Team given a bad list of players fails to create given a bad player list
     Failure/Error: expect( Team.new("Random", bad_players) ).to raise_error
     Exception:
       Exception
     # ./lib/team.rb:6:in `initialize'
     # ./spec/team_spec.rb:23:in `new'
     # ./spec/team_spec.rb:23:in `block (3 levels) in <top (required)>'

我的问题是:

1. 为什么会这样？
2. 在ruby中，前一个例子和后一个例子有什么不同？

我也在寻找rules个关于何时使用一个而不是另一个

还有一个相同但相反的结果示例，其中代码起作用:

  it "has a list of players" do
    expect(Team.new("Random").players).to be_kind_of Array
  end 

但是这个代码失败了

  it "has a list of players" do
    expect{ Team.new("Random").players }.to be_kind_of Array
  end

在这种情况下，我得到的错误是:

Failure/Error: expect{ Team.new("Random").players }.to be_kind_of Array
       expected #<Proc:0x007fbbbab29580@/Users/amiterandole/Documents/current/ruby_sandbox/tdd-ruby/spec/team_spec.rb:9> to be a kind of Array
     # ./spec/team_spec.rb:9:in `block (2 levels) in <top (required)>'

我正在测试的类如下所示:

class Team
  attr_reader :name, :players

  def initialize(name, players = [])
    raise Exception unless players.is_a? Array

    @name = name
    @players = players
  end
end