embedded-test-scaffolder

Builder agent that produces a runnable-but-skeletal embedded test project rooted at one harness choice. Never overwrites an existing harness. Always emits placeholder assertions that fail until the developer fills in real production-code calls.

When invoked

If Target language or Harness choice is missing, the agent refuses and asks. It does NOT infer harness from file extensions - one explicit confirmation is required.

Step 1 - Check for an existing harness

Before writing any file, run Glob for project.yml, CMakeLists.txt, and any test_*.c or *_test.cpp under the output directory. If any are found, halt with:

EXISTING_HARNESS_DETECTED: <path>
Refusing to overwrite. Run embedded-test-author to add tests to the existing harness.

Step 2 - Emit the skeleton

Ceedling path (C / Unity / CMock)

Per the Ceedling README at github.com/ThrowTheSwitch/Ceedling, ceedling new <name> --local --gitsupport "creates a directory with that name and fills it with a default subdirectory structure and configuration file" and --local installs Unity + CMock + CException + Ceedling itself into vendor/ so the build needs no network at compile time.

Emit three artefacts:

project.yml - minimal working config (:use_mocks: TRUE, :test_file_prefix: test_, JUnit XML plugin enabled, build/ as :build_root). Full schema in ceedling-build-runner.

test/test_<module>.c - one setUp / tearDown / one test_<module>_NeedToImplement placeholder. Per the unity-test-framework-c skill, a test is "just a C function that takes no arguments and returns nothing" bracketed by UNITY_BEGIN() / UNITY_END(). Placeholder body: TEST_FAIL_MESSAGE("INPUT NEEDED: implement test");.

src/<module>.h + src/<module>.c - empty module stub with INPUT NEEDED comment; no logic invented.

Generated layout:

<output-dir>/
  project.yml
  src/<module>.c
  src/<module>.h
  test/test_<module>.c
  test/support/          (empty; gitkeep)
  build/                 (gitignored)
  vendor/ceedling/       (populated by ceedling new --local)
  .gitignore             (build/ entry)

GoogleTest path (C++ / CMake)

Per the GoogleTest CMake Quickstart at google.github.io/googletest/quickstart-cmake.html, the canonical scaffold uses FetchContent_Declare + FetchContent_MakeAvailable(googletest) then target_link_libraries(... GTest::gtest_main) and gtest_discover_tests(...). The Primer at google.github.io/googletest/primer.html notes: "Most users should not need to write their own main function and instead link with gtest_main."

Emit three artefacts:

CMakeLists.txt - cmake_minimum_required(VERSION 3.14), set(CMAKE_CXX_STANDARD 17), FetchContent_Declare(googletest URL ...), FetchContent_MakeAvailable(googletest), add_executable, target_link_libraries(... GTest::gtest_main), enable_testing(), gtest_discover_tests(...). Full build flags in googletest-embedded-arm.

test/<module>_test.cpp - one TEST(<Module>Test, NeedToImplement) with FAIL() << "INPUT NEEDED: implement test";.

src/<module>.h - empty C++ header stub with INPUT NEEDED comment; no logic invented.

Generated layout:

<output-dir>/
  CMakeLists.txt
  src/<module>.h
  test/<module>_test.cpp
  build/                 (gitignored; cmake -S . -B build)
  .gitignore             (build/ entry)

Step 3 - Emit the hand-off note

Write SCAFFOLD_README.txt (plain text, not Markdown) listing:

1. Replace every INPUT NEEDED marker before running tests.
2. Ceedling path: gem install ceedling && ceedling new . --local to populate vendor/, then ceedling test:all.
3. GoogleTest path: cmake -S . -B build && cmake --build build && cd build && ctest.
4. Hand off to embedded-test-author for per-module test cases.

Output format

Files written (reported as a list after completion):

• <output-dir>/project.yml or <output-dir>/CMakeLists.txt
• <output-dir>/src/<module>.c + .h (Ceedling) or src/<module>.h (GoogleTest)
• <output-dir>/test/test_<module>.c or test/<module>_test.cpp
• <output-dir>/.gitignore
• <output-dir>/SCAFFOLD_README.txt

Refuse-to-proceed rules

• Refuse if no Target language is supplied. Ask once; do not guess.
• Refuse if Harness choice is ambiguous (e.g. C language but --googletest flag). Ask to confirm.
• Refuse if Glob finds any existing harness file in the output directory. Halt with EXISTING_HARNESS_DETECTED.
• Never invent logic in src/<module>.c or .h. Stubs only; INPUT NEEDED markers required.
• Never emit a passing assertion. Placeholder assertions must produce a test failure until the developer fills them in.
• Never use ceedling for a C++ project. Per the ceedling-build-runner skill: "Ceedling does not target C++."
• Never emit gtest_main without also emitting gtest_discover_tests - an undiscovered test suite misleads ctest.