packaging/nix-make: Build and run the unit tests

[edolstra]

Motivation

Build and run the unit tests with nix-make (Nix as the C++ build system), so that nix flake check ./packaging/nix-make covers them along with the functional tests.

Context

One commit per test suite (util, store, fetchers, expr, flake), each adding make.nix files for the test executable and the components it needs that nix-make did not build yet: the C APIs (lib*-c) and the test support libraries. Together with gtest, gmock and rapidcheck entries in deps.nix, that is all mkComponent needed.

A runTest helper produces a derivation that runs a test program. Every variant of the flake now has nix-<lib>-tests-run per suite and nix-all-tests, an aggregate of all unit and functional test runs; checks points at the release nix-all-tests. AGENTS.md documents the new targets.

All suites pass in the release and debug-fast variants; the release nix itself is unchanged.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Build & Testing
  • The Nix build now supports building and running unit tests alongside functional tests, either together or independently.
  • The combined test check covers additional core components and their C APIs, making broader test coverage available through the standard flake check.
  • Updated testing guidance reflects the expanded test build options.

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Essentials
• Run ID: fe547de6-389d-4a15-bea5-c0bb2c18b3b8

📥 Commits

Reviewing files that changed from the base of the PR and between 1ef9034 and 18be442.

📒 Files selected for processing (18)

• AGENTS.md
• packaging/nix-make/deps.nix
• packaging/nix-make/flake.nix
• packaging/nix-make/lib.nix
• packaging/nix-make/run-test.py
• src/libexpr-c/make.nix
• src/libexpr-test-support/make.nix
• src/libexpr-tests/make.nix
• src/libfetchers-c/make.nix
• src/libfetchers-tests/make.nix
• src/libflake-c/make.nix
• src/libflake-tests/make.nix
• src/libstore-c/make.nix
• src/libstore-test-support/make.nix
• src/libstore-tests/make.nix
• src/libutil-c/make.nix
• src/libutil-test-support/make.nix
• src/libutil-tests/make.nix

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📝 Walkthrough

Walkthrough

The change adds Nix build definitions for component unit tests and supporting libraries. It adds a reusable test runner and exposes an aggregate of unit-test runners and functional tests through nix flake check.

Changes

Nix test build and execution

Layer / File(s)	Summary
Test dependency and runner support packaging/nix-make/deps.nix, packaging/nix-make/lib.nix, packaging/nix-make/run-test.py	The dependency mappings add Google Test, Google Mock, RapidCheck, and a broader libgit2 header prefix. The library exports runTest; its Python runner loads the configured command and environment, runs the command, and creates the output directory after success.
C API and test-support components src/lib*-c/make.nix, src/lib*-test-support/make.nix	Nix component definitions add C API libraries and test-support components for the utility, store, expression, fetcher, and flake libraries.
Component unit-test executables src/libutil-tests/make.nix, src/libstore-tests/make.nix, src/libfetchers-tests/make.nix, src/libexpr-tests/make.nix, src/libflake-tests/make.nix	Nix expressions define unit-test executables and their test runs, including configured dependencies, test data, and environment values. The utility tests also define a run that disables openat2 and fchmodat2 through enosys.
Aggregate test check and guidance packaging/nix-make/flake.nix, AGENTS.md	The flake adds unit-test runners to nix-all-tests alongside functional tests, exposes the aggregate through checks, and re-exports the built-in checks schema. The testing guidance documents the all-tests build command and independent suite builds.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant NixFlakeCheck
  participant nix-all-tests
  participant runTest
  participant run-test.py
  participant nix-util-tests
  NixFlakeCheck->>nix-all-tests: builds the aggregate check
  nix-all-tests->>runTest: includes unit-test runner derivations
  runTest->>run-test.py: starts the configured test command
  run-test.py->>nix-util-tests: executes the unit-test binary

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Merge Risk: ⚪ Minimal · up to 18be4

This change adds unit-test builds and runs to the flake check without changing the shipped Nix binary. No concrete merge-blocking risk was identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (17 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the primary change: adding build and run support for unit tests in packaging/nix-make.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (17 skipped: 17 unsupported.)

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✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

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