Add timeouts to ExUnit, closes #2660

Author: José Valim

lib/ex_unit/lib/ex_unit.ex

@@ -109,6 +109,15 @@ defmodule ExUnit do
                  tests: [ExUnit.Test.t]}
   end
 
+  defmodule TimeoutError do
+    defexception [:timeout]
+
+    def message(%{timeout: timeout}) do
+      "test timed out after #{timeout}ms (you can change the test timeout " <>
+        "by setting \"@tag timeout: x\" where x is an integer in miliseconds)"
+    end
+  end
+
   use Application
 
   @doc false

lib/ex_unit/lib/ex_unit/runner.ex

@@ -208,12 +208,18 @@ defmodule ExUnit.Runner do
         exit(:shutdown)
       end)
 
+    timeout = Map.get(test.tags, :timeout, 30_000)
+
     test =
       receive do
         {^test_pid, :test_finished, test} ->
           test
         {:DOWN, ^test_ref, :process, ^test_pid, error} ->
           %{test | state: {:failed, {{:EXIT, test_pid}, error, []}}}
+      after
+        timeout ->
+          Process.exit(test_pid, :kill)
+          %{test | state: {:failed, {:error, %ExUnit.TimeoutError{timeout: timeout}, []}}}
       end
 
     exec_on_exit(test, test_pid)

lib/ex_unit/test/ex_unit_test.exs

@@ -40,6 +40,20 @@ defmodule ExUnitTest do
     end) =~ "1 tests, 1 failures"
   end
 
+  test "it supports timeouts" do
+    defmodule TimeoutTest do
+      use ExUnit.Case
+
+      @tag timeout: 10
+      test "ok" do
+        :timer.sleep(:infinity)
+      end
+    end
+
+    assert capture_io(fn -> ExUnit.run end) =~
+           "** (ExUnit.TimeoutError) test timed out after 10ms"
+  end
+
   test "filtering cases with tags" do
     defmodule ParityTest do
       use ExUnit.Case