erlang - 在 erlang eunit failure 中打印测试夹具描述

Question

有没有办法打印使用fixtures的erlang测试生成器的测试描述？使用生成器很难判断哪个测试实际上失败了，打印描述会有所帮助。

例子:

-module(math_test).

-include_lib("eunit/include/eunit.hrl").
-define(test(Desc, F), {Desc, {setup, fun setup/0, fun cleanup/1, F}}).

setup() ->
  ok.

cleanup(_) ->
  ok.

math_test_ () ->
  [
    ?test("adds two numbers", fun add_two_numbers/0),
    ?test("subtract two numbers", fun subtract_two_numbers/0),
    ?test("undefined method called", fun undefined_error/0)
  ].

add_two_numbers () ->
  ?assertEqual(2, 1 + 3).

subtract_two_numbers () ->
  ?assertEqual(1, 2 - 2).

undefined_error () ->
  undefined_module:uh_oh().

然后运行它

[root@a7c901c022bb src]# rebar3 eunit --module=math_test
===> Verifying dependencies...
===> Compiling math
===> Performing EUnit tests...
FFF
Failures:

  1) math_test:math_test_/0
     Failure/Error: ?assertEqual(2, 1 + 3)
       expected: 2
            got: 4
     %% /src/_build/test/lib/math/src/math_test.erl:20:in `math_test:-add_two_numbers/0-fun-0-/1`
     Output: 
     Output: 
  2) math_test:math_test_/0
     Failure/Error: ?assertEqual(1, 2 - 2)
       expected: 1
            got: 0
     %% /src/_build/test/lib/math/src/math_test.erl:23:in `math_test:-subtract_two_numbers/0-fun-0-/1`
     Output: 
     Output: 
  3) math_test:math_test_/0
     Failure/Error: {error,undef,[{undefined_module,uh_oh,[],[]}]}
     Output: 

前 2 个错误没问题，但不是很好——您至少可以在断言中看到实际出错的地方。

然而，第三个错误(调用未定义的模块/方法)是非常错误的地方——没有真正的方法来判断它来自哪里!

有没有办法改进，比如打印测试描述和失败日志？

Answer 1

您可以做的一件事是将测试描述放在测试本身上，而不是整个 setup 元组。即，更改此行:

-define(test(Desc, F), {Desc, {setup, fun setup/0, fun cleanup/1, F}}).

到:

-define(test(Desc, F), {setup, fun setup/0, fun cleanup/1, {Desc, F}}).

随着这个改变，测试描述被打印出来:

Failures:

  1) math_test:math_test_/0: adds two numbers
     Failure/Error: ?assertEqual(2, 1 + 3)
       expected: 2
            got: 4
     %% /tmp/math_test/mylib/_build/test/lib/mylib/test/math_test.erl:20:in `math_test:-add_two_numbers/0-fun-0-/0`
     Output: 
     Output: 
  2) math_test:math_test_/0: subtract two numbers
     Failure/Error: ?assertEqual(1, 2 - 2)
       expected: 1
            got: 0
     %% /tmp/math_test/mylib/_build/test/lib/mylib/test/math_test.erl:23:in `math_test:-subtract_two_numbers/0-fun-0-/0`
     Output: 
     Output: 
  3) math_test:math_test_/0: undefined method called
     Failure/Error: {error,undef,[{undefined_module,uh_oh,[],[]}]}
     Output: 

---

要尝试的另一件事是使用 ?_test 宏而不是普通的 fun 术语指定测试函数:

math_test_ () ->
  [
    ?test("adds two numbers", ?_test(add_two_numbers())),
    ?test("subtract two numbers", ?_test(subtract_two_numbers())),
    ?test("undefined method called", ?_test(undefined_error()))
  ].

?_test 宏会记住它出现的行号，并在测试失败时将其包含在输出中:

  1) math_test:math_test_/0:14: adds two numbers
  [...]
  2) math_test:math_test_/0:15: subtract two numbers
  [...]
  3) math_test:math_test_/0:16: undefined method called
  [...]

现在您可以知道从哪一行调用了这些测试。

---

另一种方法是让各个函数返回 eunit“测试对象”，而不是仅仅运行测试。这将涉及使用 ?_assertEqual 而不是 ?assertEqual，或者将整个内容包装在 ?_test 中:

math_test_ () ->
  [
    ?test("adds two numbers", add_two_numbers()),
    ?test("subtract two numbers", subtract_two_numbers()),
    ?test("undefined method called", undefined_error())
  ].

add_two_numbers () ->
  ?_assertEqual(2, 1 + 3).

subtract_two_numbers () ->
  ?_assertEqual(1, 2 - 2).

undefined_error () ->
  ?_test(undefined_module:uh_oh())

然后输出包含行号和各个测试函数的名称:

Failures:

  1) math_test:add_two_numbers/0:20: adds two numbers
     Failure/Error: ?assertEqual(2, 1 + 3)
       expected: 2
            got: 4
     %% /tmp/math_test/mylib/_build/test/lib/mylib/test/math_test.erl:20:in `math_test:-add_two_numbers/0-fun-0-/0`
     Output: 
     Output: 
  2) math_test:subtract_two_numbers/0:23: subtract two numbers
     Failure/Error: ?assertEqual(1, 2 - 2)
       expected: 1
            got: 0
     %% /tmp/math_test/mylib/_build/test/lib/mylib/test/math_test.erl:23:in `math_test:-subtract_two_numbers/0-fun-0-/0`
     Output: 
     Output: 
  3) math_test:undefined_error/0:26: undefined method called
     Failure/Error: {error,undef,[{undefined_module,uh_oh,[],[]}]}
     Output: