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name: supertester-otp-testing description: This skill should be used when teams need to adopt Supertester to build deterministic Elixir OTP tests with isolation, synchronization, and supervision coverage. license: Complete terms in LICENSE

Supertester OTP Testing

When To Trigger

• Activate whenever writing or reviewing new OTP-heavy tests so Supertester foundations are considered before adding bespoke helpers.
• Activate when eliminating flaky OTP tests, Process.sleep/1 calls, or race conditions in Elixir suites.
• Activate when installing or upgrading Supertester and clarifying how OTP helpers should shape new or existing tests.
• Activate when validating supervision restarts, chaos scenarios, or performance contracts with Supertester-provided tooling.

Core Goals

• Establish isolation with Supertester.UnifiedTestFoundation and run OTP tests safely with async: true.
• Retrofit GenServers and supervisors to use deterministic synchronization via Supertester helpers.
• Replace bespoke OTP utilities with the official helpers and assertions in lib/supertester.
• Surface reusable diagnostics that make failures obvious and repeatable.

Quick Orientation

• Review README.md for feature highlights and before/after examples.
• Use MANUAL.md for full API coverage; jump to the “OTP Testing Helpers” section for signatures.
• Keep docs/QUICK_START.md on hand for migration recipes and example code.
• Inspect source modules directly (lib/supertester/otp_helpers.ex, lib/supertester/genserver_helpers.ex, lib/supertester/unified_test_foundation.ex, lib/supertester/testable_genserver.ex, lib/supertester/assertions.ex) whenever implementation details matter.

Setup Workflow

1. Add {:supertester, "~> 0.2.1", only: :test} to mix.exs and run mix deps.get to install.
2. Use Supertester.UnifiedTestFoundation in each OTP-heavy test module, defaulting to isolation: :full_isolation unless constraints require lighter modes.
3. Import helper namespaces explicitly:

   import Supertester.OTPHelpers
   import Supertester.GenServerHelpers
   import Supertester.Assertions
   

4. Mark eligible cases async: true (automatically supplied by the isolation macro) and rely on helper-driven cleanup instead of manual teardown.

GenServer Workflow

• Start isolated servers via setup_isolated_genserver/3, passing custom :init_args or explicit names through opts.
• Apply use Supertester.TestableGenServer inside target modules to expose the __supertester_sync__ handler without redefining handle_call/3.
• Replace bare casts with cast_and_sync/3 followed by assert_genserver_state/2 or assert_genserver_responsive/1.
• Leverage call_with_timeout/3, get_server_state_safely/1, monitor_process_lifecycle/1, and cleanup_on_exit/1 to observe asynchronous behavior deterministically.

Example Pattern

defmodule MyApp.CounterTest do
  use ExUnit.Case
  use Supertester.UnifiedTestFoundation, isolation: :full_isolation

  import Supertester.OTPHelpers
  import Supertester.GenServerHelpers
  import Supertester.Assertions

  test "increments without race conditions" do
    {:ok, counter} = setup_isolated_genserver(MyApp.Counter)

    :ok = cast_and_sync(counter, :increment)
    assert_genserver_state(counter, fn state -> state.count == 1 end)
  end
end

Supervisor & Restart Testing

• Start trees with setup_isolated_supervisor/3 and confirm readiness through wait_for_supervisor_restart/2 or wait_for_supervisor_stabilization/2.
• Probe restart semantics using test_restart_strategy/3, then assert outcomes with helpers such as assert_process_restarted/2 and assert_all_children_alive/1.
• Trace living supervision events via trace_supervision_events/2 to capture restarts without manual logging.
• Enable isolation: :contamination_detection when diagnosing leaks; review warnings emitted by Supertester.UnifiedTestFoundation.

Chaos And Performance Hooks

• Exercise resilience with Supertester.ChaosHelpers, following scenario setups in README.md and option references in MANUAL.md.
• Guard service-level objectives using Supertester.PerformanceHelpers, pairing assert_performance/2 or assert_no_memory_leak/2 with isolated fixtures.

Assertions & Diagnostics

• Favor OTP-aware checks from lib/supertester/assertions.ex (assert_genserver_handles_message/3, assert_process_dead/1, assert_no_process_leaks/1) instead of bespoke assertions.
• Run verify_test_isolation/1 when isolations feel suspect to confirm all tracked processes remain sandboxed.
• Capture process exits intentionally with wait_for_process_death/2 and translate restarts to deterministic expectations.

Reference Bundle

• Load MANUAL.md#otp-testing-helpers for signature verification mid-task.
• Consult docs/API_GUIDE.md for extended examples and edge-case notes.
• Check CHANGELOG.md before depending on newer APIs or behavior changes.

Reuse Checklist

• Confirm each GenServer under test use Supertester.TestableGenServer.
• Ensure every asynchronous assertion flows through cast_and_sync/3, wait_for_genserver_sync/2, or equivalent helpers.
• Replace any remaining Process.sleep/1 usage with Supertester synchronization.
• Remove redundant in-house OTP helpers once the Supertester equivalents are adopted.