The tester directory implements a pseudo-component inside the SOF architecture. Instead of processing audio like an EQ or Mixer, it acts as a test execution harness designed specifically for Continuous Integration (CI) and automated system verifications.

Continuous integration often requires validating low-level system interactions that cannot be reached or easily triggered via standard ALSA driver behaviors. To overcome this, the tester component can be instantiated via Topologies or explicit IPC commands. Once bound, the host can send configuration blobs triggering embedded testing subroutines compiled directly into the firmware.

Currently, it supports functionalities like:

• Dummy Operations: Echoing parameters to verify full-stack serialization roundtrips.
• DRAM Verification: Stress-testing memory allocation arrays within the LLB/L2 domains to detect caching bugs or out-of-bounds pointer crashes (tester_simple_dram_test).

The architecture functions identical to an IPC Version 4 standard module, containing comp_driver, comp_dev, comp_buffer wrappers and implementing tester_params() handlers.

graph TD
    subgraph Host Automation
        Testbench[CI Testbench / ALSA Tool]
        Testbench -->> |Topology Payload: CMD_TEST| IPC
    end

    subgraph SOF Firmware
        IPC[IPC4 Handler] -->> |ipc4_set_module_params| Tester[Tester Component]

        Tester -->> |Switch on Test Type| Dummy[tester_dummy_test.c]
        Tester -->> |Switch on Test Type| DRAM[tester_simple_dram_test.c]

        Dummy -->> IPC
        DRAM -->> |Runs Data Verifications| ExtMemory[SoC DRAM / Caches]
        DRAM -->> IPC
    end

Because the tester artificially exposes internal memory bounds limits and allows arbitrary firmware injection tests, it is locked out of standard release payloads.

To compile it into your build, you must append:

• CONFIG_COMP_TESTER=y

Constraints: It strictly depends on IPC_MAJOR_4. You cannot instantiate this tester under the legacy IPC3 streaming mechanisms.

Developers diagnosing tricky hardware bugs can extend the tester by:

1. Adding a new case to the test selection switch in tester.c:tester_init() (and, if needed, extending runtime handling in tester_set_configuration()).
2. Defining a new test_runner() C file implementing their data patterns.
3. Adding the target configurations in tester.toml to automatically sync with the module offset calculators (llext_offset_calc).