UPDATE: hauleth mentions me a better solution in ElixirForum. So, I updated this article.
I found a way which is parameterized testing with ExUnit.
ExUnit.start() defmodule ParameterizedTest do use ExUnit.Case, async: true for {lhs, rhs} <- [{"one", 1}, {"two", 2}, {"three", 3}] do test "#{lhs} convert to #{rhs}" do assert unquote(lhs) === unquote(rhs) end end end 1) test one convert to 1 (ParameterizedTest) parameterized_test.exs:7 Assertion with === failed code: assert "one" === 1 left: "one" right: 1 stacktrace: parameterized_test.exs:8: (test) 2) test three convert to 3 (ParameterizedTest) parameterized_test.exs:7 Assertion with === failed code: assert "three" === 3 left: "three" right: 3 stacktrace: parameterized_test.exs:8: (test) 3) test two convert to 2 (ParameterizedTest) parameterized_test.exs:7 Assertion with === failed code: assert "two" === 2 left: "two" right: 2 stacktrace: parameterized_test.exs:8: (test) Finished in 0.03 seconds (0.03s on load, 0.00s on tests) 3 tests, 3 failures Randomized with seed 169786 The Probrem
We can't pass variables from outside into the block of tests directly.
ExUnit.start() defmodule ParameterizedTest do use ExUnit.Case, async: true for {lhs, rhs} <- [{"one", 1}, {"two", 2}, {"three", 3}] do test "#{lhs} convert to #{rhs}" do assert lhs === rhs # We can't use their variables here. end end end ** (CompileError) parameterized_test.exs:8: undefined function lhs/0 (stdlib) lists.erl:1338: :lists.foreach/2 Other solutions
Use assertions instead of tests
Assertions and tests work well. But, ExUnit shows only one message per test. So, If you desire showing outline of tests. It does not match well.
ExUnit.start() defmodule ParameterizedTest do use ExUnit.Case, async: true test "convert" do for {lhs, rhs} <- [{"one", 1}, {"two", 2}, {"three", 3}] do assert lhs === rhs end end end 1) test convert (ParameterizedTest) parameterized_test.exs:6 Assertion with === failed code: assert lhs === rhs left: "one" right: 1 stacktrace: parameterized_test.exs:8: anonymous fn/2 in ParameterizedTest."test convert"/1 (elixir) lib/enum.ex:1925: Enum."-reduce/3-lists^foldl/2-0-"/3 parameterized_test.exs:7: (test) Finished in 0.03 seconds (0.03s on load, 0.00s on tests) 1 test, 1 failure Randomized with seed 303559 Use module attributes
Tests work well. But, module attributes breaks scope. So, you have to keep module attribute in mind after using it.
ExUnit.start() defmodule ParameterizedTest do use ExUnit.Case, async: true for {lhs, rhs} <- [{"one", 1}, {"two", 2}, {"three", 3}] do @pair {lhs, rhs} test "#{lhs} convert to #{rhs}" do {l, r} = @pair assert l === r end end test "pair should not have any value" do assert nil === @pair # We don't expect getting any values end end 1) test pair should not have any value (ParameterizedTest) parameterized_test.exs:15 Assertion with === failed code: assert nil === @pair left: nil right: {"three", 3} stacktrace: parameterized_test.exs:16: (test) 2) test three convert to 3 (ParameterizedTest) parameterized_test.exs:9 Assertion with === failed code: assert l === r left: "three" right: 3 stacktrace: parameterized_test.exs:11: (test) 3) test two convert to 2 (ParameterizedTest) parameterized_test.exs:9 Assertion with === failed code: assert l === r left: "two" right: 2 stacktrace: parameterized_test.exs:11: (test) 4) test one convert to 1 (ParameterizedTest) parameterized_test.exs:9 Assertion with === failed code: assert l === r left: "one" right: 1 stacktrace: parameterized_test.exs:11: (test) Finished in 0.04 seconds (0.04s on load, 0.00s on tests) 4 tests, 4 failures Randomized with seed 936081 Use ex_parameterized
https://github.com/KazuCocoa/ex_parameterized makes allow parameterized testing following:
defmodule MyExampleTest do use ExUnit.Case, async: true use ExUnit.Parameterized # Required test_with_params "add params", # description fn (a, b, expected) -> # test case assert a + b == expected end do [ {1, 2, 3}, # parameters "description": {1, 4, 5}, # parameters with description ] end end I like this idea. But this time, I have wanted to write ExUnit test cases with only standard libraries.
Use ExUnit.Case.register_test/4
Registers a new attribute to be used during ExUnit.Case tests.
The attribute values will be available as a key/value pair in context.registered. The key/value pairs will be cleared after each ExUnit.Case.test/3 similar to @tag.
ExUnit.start() defmodule ParameterizedTest do use ExUnit.Case, async: true ExUnit.Case.register_attribute __ENV__, :pair for {lhs, rhs} <- [{"one", 1}, {"two", 2}, {"three", 3}] do @pair {lhs, rhs} test "#{lhs} convert to #{rhs}", context do {l, r} = context.registered.pair assert l === r end end test "pair should not have any value" do assert nil === @pair end end warning: undefined module attribute @pair, please remove access to @pair or explicitly set it before access parameterized_test.exs:18: ParameterizedTest (module) . 1) test two convert to 2 (ParameterizedTest) parameterized_test.exs:11 Assertion with === failed code: assert l === r left: "two" right: 2 stacktrace: parameterized_test.exs:13: (test) 2) test one convert to 1 (ParameterizedTest) parameterized_test.exs:11 Assertion with === failed code: assert l === r left: "one" right: 1 stacktrace: parameterized_test.exs:13: (test) 3) test three convert to 3 (ParameterizedTest) parameterized_test.exs:11 Assertion with === failed code: assert l === r left: "three" right: 3 stacktrace: parameterized_test.exs:13: (test) Finished in 0.05 seconds (0.05s on load, 0.00s on tests) 4 tests, 3 failures Randomized with seed 385498 It works well, outline of tests, scope about variables and only using standard libraries. Actually, this solution is written on the top of this article before I update. But I feel codes a little bit verbose. for example: {l, r} = context.registered.pair.
Top comments (1)
面白いです！Thank you for sharing this.