測試異常

執行測試時遇到的異常將導致測試失敗，如果測試不在測試集中，則終止測試引擎。通常，這是一件好事，因為在大多數情況下，異常並不是理想的結果。但有時候，人們想要特別測試是否會引發某種異常。@test_throws 巨集有利於此。

julia> @test_throws BoundsError [1, 2, 3][4]
Test Passed
  Expression: ([1,2,3])[4]
      Thrown: BoundsError

如果丟擲了錯誤的異常，@test_throws 仍然會失敗：

julia> @test_throws TypeError [1, 2, 3][4]
Test Failed
  Expression: ([1,2,3])[4]
    Expected: TypeError
      Thrown: BoundsError
ERROR: There was an error during testing
 in record(::Base.Test.FallbackTestSet, ::Base.Test.Fail) at ./test.jl:397
 in do_test_throws(::Base.Test.Threw, ::Expr, ::Type{T}) at ./test.jl:329

如果沒有丟擲異常，@test_throws 也會失敗：

julia> @test_throws BoundsError [1, 2, 3, 4][4]
Test Failed
  Expression: ([1,2,3,4])[4]
    Expected: BoundsError
  No exception thrown
ERROR: There was an error during testing
 in record(::Base.Test.FallbackTestSet, ::Base.Test.Fail) at ./test.jl:397
 in do_test_throws(::Base.Test.Returned, ::Expr, ::Type{T}) at ./test.jl:329