Ulf Wiger
140 lines
4.2 KiB
Markdown
140 lines
4.2 KiB
Markdown
gm_ctflow
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=====
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A helper application for cross-testcase test flows in Common Test
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Description
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----
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When testing complex systems it often feels convenient to organize test
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sequences as a sequential group where a series of test cases perform a
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flow of operations. A challenge may arise when the results from one
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test case need to be reused by later cases - Common Test does cater for
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this through the `save_config` return.
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However, occasionally, one also needs to have bespoke servers running
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for the duration of such a sequence, and this tends to lead to hacking
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a plain process with a custom protocol.
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This application attempts to make that a bit more structured.
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In its initial version, there are a few different APIs:
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* `gm_ctflow_fun`, where one can instantiate a stateful handler fun,
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which can be called by test cases as needed.
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* `gm_ctflow_worker`, a gen_server where the server logic is given
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by a user-provided fun. The server is spawned under a
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`simple_one_for_one` supervisor.
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* `gm_ctflow_reg`, used to register and find `gm_ctflow_worker` processes.
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Complies with the `via` addressing scheme for OTP behaviors.
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* `gm_ctflow`, providing a shared dictionary, logging and status support.
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The application `gm_ctflow` is intended to be started in
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`init_per_suite/1` and stopped in `end_per_suite/1`, or in
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`init_per_group/2` / `end_per_group/2`.
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Some examples from `test/gm_ctflow_SUITE.erl`:
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```erlang
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groups() ->
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[ {statefuns, [sequence], [ init_counter
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, incr
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, check1 %% state = 1
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, incr
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, check2 %% state = 2
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, incr
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, check3 %% state = 3
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]}
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, {workers, [sequence], [ init_counter
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, init_worker
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, append
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, checkl1 %% [A0]
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, append
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, checkl2 %% [A0, A1]
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, append
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, checkl3 %% [A0, A1, A2]
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]}
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].
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```
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Here, we interleave test cases with checks of the flow fun states.
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This test suite does nothing but exercize the flow funs, but normally,
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these funs would be used to e.g. spawn an endpoint needed for the tests,
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or thread some state through a test sequence.
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The `gm_ctflow` application is started and stopped per-group here:
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```erlang
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init_per_group(_Grp, Config) ->
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ok = application:start(gm_ctflow, permanent),
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Config.
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end_per_group(_Grp, _Config) ->
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ok = application:stop(gm_ctflow),
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ok.
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```
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This resets the state and removes all helper processes for each group.
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A simple way to keep track of the flow state:
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```erlang
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init_per_testcase(_Case, Config) ->
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gm_ctflow:status(),
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Config.
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end_per_testcase(_Case, _Config) ->
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gm_ctflow:status(),
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ok.
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```
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This gives output like this, from the `gm_ctflow_SUITE:incr/1` testcase:
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```
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*** User 2026-05-30 13:06:02.679 ***🔗
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== Summary for flow my_counter
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= Worker State: - none -
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= Fun State: 0
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= State: - none -
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= Log History:
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2026-05-30 13:06:02.654:
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New flow: my_counter
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*** User 2026-05-30 13:06:02.679 ***🔗
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my_counter[<0.332.0>]: F(incr, 0) -> {ok,1,1}
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*** User 2026-05-30 13:06:02.679 ***🔗
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== Summary for flow my_counter
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= Worker State: - none -
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= Fun State: 1
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= State: - none -
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= Log History:
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2026-05-30 13:06:02.654:
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New flow: my_counter
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2026-05-30 13:06:02.679:
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F(incr, 0) -> {ok,1,1}
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```
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Normally, of course, there would be more going on in the test, making the
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bookends a bit less dominant, but here we see the initial state of the flow
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`my_counter`: The "Fun state" is `0`, while there's no worker, and no shared state.
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The log history shows one previous message, from instantiating the fun.
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The next log output shows the effect of calling the fun. Log messages produced
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with `gm_ctflow:ct_log/[2,3]` go both to `ct:log/2` and the log history. The
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flow is derived automatically, if possible, if not provided.
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In the ending `status` output, we see the accumulated history, with timestamps
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to make it easier to find the context in CT or SUT logs.
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Build
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-----
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$ rebar3 compile
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Test
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-----
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$ rebar ct
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