Configuration Resolution: What is read and when

This document explains how configuration is loaded, merged, and provided to tests and interfaces.

Sources and precedence

From highest to lowest precedence:

In-code overrides (if load_config(..., overrides=...) is used)
Environment variable ECU_TESTS_CONFIG (absolute/relative path to YAML)
config/test_config.yaml (if present under the workspace root)
Built-in defaults

Data model (dataclasses)

EcuTestConfig
- interface: InterfaceConfig
  - type: mock or babylin
  - channel: LIN channel index (0-based in SDK wrapper)
  - bitrate: LIN bitrate (e.g., 19200); usually defined by SDF
  - sdf_path: Path to SDF file (hardware; required for typical operation)
  - schedule_nr: Schedule number to start on connect (hardware)
  - node_name: Optional node identifier (informational)
  - dll_path, func_names: Legacy fields from the old ctypes adapter; not used with the SDK wrapper
- flash: FlashConfig
  - enabled: whether to flash before tests
  - hex_path: path to HEX file

YAML examples

Minimal mock configuration (default):

interface:
  type: mock
  channel: 1
  bitrate: 19200
flash:
  enabled: false

Hardware (BabyLIN SDK wrapper) configuration:

interface:
  type: babylin
  channel: 0                    # 0-based channel index
  bitrate: 19200                # optional; typically driven by SDF
  node_name: "ECU_TEST_NODE"
  sdf_path: "./vendor/Example.sdf"
  schedule_nr: 0
flash:
  enabled: true
  hex_path: "firmware/ecu_firmware.hex"

Load flow

tests/conftest.py: config() fixture
  → load_config(workspace_root)
    → check env var ECU_TESTS_CONFIG
    → else check config/test_config.yaml
    → else use defaults
  → convert dicts to EcuTestConfig dataclasses
  → provide to other fixtures/tests

How tests and adapters consume config

lin fixture picks mock or babylin based on interface.type
Mock adapter uses bitrate and channel to simulate timing/behavior
BabyLIN adapter (SDK wrapper) uses sdf_path, schedule_nr, channel to open the device, load the SDF, and start a schedule. bitrate is informational unless explicitly applied via commands/SDF.
flash_ecu uses flash.enabled and flash.hex_path

Tips

Keep multiple YAMLs and switch via ECU_TESTS_CONFIG
Check path validity for sdf_path and hex_path before running hardware tests
Ensure vendor/BabyLIN_library.py and the platform-specific libraries from the SDK are available on PYTHONPATH
Use environment-specific YAML files for labs vs. CI

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