NoMethodError：未定義的方法`RuntimeError'當我使用{...}語法代替do ... end with minitest

Question

我正在使用minitest來測試引發異常的方法。我使用了在​​中描述的技術，但我有一些混亂的結果：

代碼：

class Formatter 
    def output_report 
    raise "Abstract method called: #{__method__}" 
    end 
end 

測試：

require 'minitest/autorun' 
require_relative 'formatter' 

class TestFormatter < Minitest::Test 
    def setup 
    @formatter = Formatter.new 
    end 

    def test_formatter_error_when_abstract_method_called 
    err = assert_raises RuntimeError { @formatter.output_report } 
    assert_equal "Abstract method called: output_report", err.message 
    end 
end 

我預期測試通過​​，除了相反，我得到了以下錯誤：

Run options: --seed 64742 

# Running: 

E 

Finished in 0.001274s, 784.9294 runs/s, 0.0000 assertions/s. 

    1) Error: 
TestFormatter#test_formatter_error_when_abstract_method_called: 
NoMethodError: undefined method `RuntimeError' for #<TestFormatter:0x007fd07a2b93d0> 
    test_formatter.rb:10:in `test_formatter_error_when_abstract_method_called' 

1 runs, 0 assertions, 0 failures, 1 errors, 0 skips 

但是，如果我使用do...end塊語法，而不是{...}，則測試通過

做...結束：

require 'minitest/autorun' 
require_relative 'formatter' 

class TestFormatter < Minitest::Test 
    def setup 
    @formatter = Formatter.new 
    end 

    def test_formatter_error_when_abstract_method_called 
    # err = assert_raises RuntimeError { @formatter.output_report } 
    err = assert_raises RuntimeError do 
     @formatter.output_report 
    end 
    assert_equal "Abstract method called: output_report", err.message 
    end 
end 

輸出：

Run options: --seed 37315 

# Running: 

. 

Finished in 0.001298s, 770.4160 runs/s, 1540.8321 assertions/s. 

1 runs, 2 assertions, 0 failures, 0 errors, 0 skips 

這究竟是爲什麼？我認爲do...end等於{...}，除了在製作多行塊時使用前者的慣例？

Answer 1

do..end和{...}之間有顯着性差異：優先事項很重要。捲毛是貪婪的，do...end不是。

人爲的例子：

puts [1].each { |i| i } #⇒ 1 
puts [1].each do |i| i end #⇒ #<Enumerator:0x000000067dd678> 

這就是說，要使花括號按預期方式工作，應該使用圓括號：

assert_raises(RuntimeError) { @formatter.output_report }