Why does an ets table survive ct:init_per_testcase but not init_per_suite?

common-test, erlang, testing

Solution

As was already mentioned in the answer by Pascal and as discussed in the User Guide only `init_per_testcase` and `end_per_testcase` run in the same process as the testcase. Since ETS tables are bound to a owner process your only way to have a ETS table persist during a whole suite or group is to give it away or define a heir process.

You can easily spawn a process in your `init_per_suite` or `init_per_group` functions, set it as heir for the ETS table and pass its pid along in the config.

To clean up all you need is to kill this process in your `end_per_suite` or `end_per_group` functions.

-module(an_example_SUITE).
-include_lib("common_test/include/ct.hrl").

-compile(export_all).

all() -> [ets_tests].

ets_owner() ->
    receive
        stop -> exit(normal);
        Any -> ets_owner()
    end.

init_per_suite(Config) ->
    Pid = spawn(fun ets_owner/0),
    TabId = ets:new(conns, [set, protected, {heir, Pid, []}]),
    ets:insert(TabId, {foo, 2131}),
    [{table,TabId},{table_owner, Pid} | Config].

end_per_suite(Config) ->
    ?config(table_owner, Config) ! stop.

ets_tests(Config) ->
    TabId = ?config(table, Config),
    [{foo, 2131}] = ets:lookup(TabId, foo).

You also need to make sure you can still access your table from the testcase process, by making it either `protected`or `public`

Problem

Original source