test: replace custom cfg with TEST_SKIP environment variable (#372)

* refactor(test): replace `pdu_test_skip_fs_errors` cfg with `TEST_SKIP` env var

The custom cfg flag required `RUSTFLAGS` which forced full recompilation
just to skip a test. The new `TEST_SKIP` env var passes `--skip` to the
test binary at runtime, avoiding any recompilation.

https://claude.ai/code/session_01UBzLwHNmqEC2SafFKjEqYz

* fix(test): clarify hint to mention ./test.sh for TEST_SKIP

The TEST_SKIP variable is only interpreted by test.sh, not by cargo
test directly. Update the hint to say "rerun via ./test.sh" so users
know exactly how to invoke it.

https://claude.ai/code/session_01UBzLwHNmqEC2SafFKjEqYz

* docs(contributing): remove redundant TEST_SKIP guideline

The paragraph framed TEST_SKIP as a general policy for writing new
tests, but there is only one such test. The test's own panic hint
and the existing note in the test-running section already provide
sufficient guidance.

https://claude.ai/code/session_01UBzLwHNmqEC2SafFKjEqYz

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: KSXGitHub

.github/copilot-instructions.md

@@ -16,6 +16,6 @@ Read and follow the CONTRIBUTING.md file in this repository for all code style c
 - Minimize `unwrap()` in non-test code — use proper error handling
 - Prefer `#[cfg_attr(..., ignore = "reason")]` over `#[cfg(...)]` to skip tests — use `#[cfg]` on tests only when the code cannot compile under the condition (e.g., references types/functions that don't exist on other platforms)
 - Install toolchain before running tests: `rustup toolchain install "$(< rust-toolchain)" && rustup component add --toolchain "$(< rust-toolchain)" rustfmt clippy`
-- Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*`, follow the hint and rerun with the suggested flags.
+- Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `TEST_SKIP`, follow the hint and rerun with the suggested variable.
 - **ALWAYS run the full test suite** (`FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh`) before committing, regardless of how trivial the change seems — this includes documentation-only changes, comment edits, config changes, and refactors. The test suite checks formatting, linting, building, tests, and docs across multiple feature combinations; any type of change can break any of these checks.
 - Set `PDU_NO_FAIL_FAST=true` to run all checks instead of stopping at the first failure — this lets you see which checks pass and which fail

AGENTS.md

@@ -16,6 +16,6 @@ Read and follow the CONTRIBUTING.md file in this repository for all code style c
 - Minimize `unwrap()` in non-test code — use proper error handling
 - Prefer `#[cfg_attr(..., ignore = "reason")]` over `#[cfg(...)]` to skip tests — use `#[cfg]` on tests only when the code cannot compile under the condition (e.g., references types/functions that don't exist on other platforms)
 - Install toolchain before running tests: `rustup toolchain install "$(< rust-toolchain)" && rustup component add --toolchain "$(< rust-toolchain)" rustfmt clippy`
-- Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*`, follow the hint and rerun with the suggested flags.
+- Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `TEST_SKIP`, follow the hint and rerun with the suggested variable.
 - **ALWAYS run the full test suite** (`FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh`) before committing, regardless of how trivial the change seems — this includes documentation-only changes, comment edits, config changes, and refactors. The test suite checks formatting, linting, building, tests, and docs across multiple feature combinations; any type of change can break any of these checks.
 - Set `PDU_NO_FAIL_FAST=true` to run all checks instead of stopping at the first failure — this lets you see which checks pass and which fail

CLAUDE.md

@@ -16,7 +16,7 @@ Read and follow the CONTRIBUTING.md file in this repository for all code style c
 - Minimize `unwrap()` in non-test code — use proper error handling
 - Prefer `#[cfg_attr(..., ignore = "reason")]` over `#[cfg(...)]` to skip tests — use `#[cfg]` on tests only when the code cannot compile under the condition (e.g., references types/functions that don't exist on other platforms)
 - Install toolchain before running tests: `rustup toolchain install "$(< rust-toolchain)" && rustup component add --toolchain "$(< rust-toolchain)" rustfmt clippy`
-- Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*`, follow the hint and rerun with the suggested flags.
+- Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `TEST_SKIP`, follow the hint and rerun with the suggested variable.
 - **ALWAYS run the full test suite** (`FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh`) before committing, regardless of how trivial the change seems — this includes documentation-only changes, comment edits, config changes, and refactors. The test suite checks formatting, linting, building, tests, and docs across multiple feature combinations; any type of change can break any of these checks.
 - Set `PDU_NO_FAIL_FAST=true` to run all checks instead of stopping at the first failure — this lets you see which checks pass and which fail
 - `gh` (GitHub CLI) is not installed — do not attempt to use it

CONTRIBUTING.md

@@ -215,7 +215,7 @@ pub enum RuntimeError {
 
 ### Conditional Test Skipping: `#[cfg]` vs `#[cfg_attr(..., ignore)]`
 
-When a test cannot run under certain conditions (e.g., wrong platform, running as root), prefer `#[cfg_attr(..., ignore)]` over `#[cfg(...)]` to skip it. This way the test is still compiled on all configurations — catching type errors and regressions early — but simply skipped at runtime.
+When a test cannot run under certain conditions (e.g., wrong platform), prefer `#[cfg_attr(..., ignore)]` over `#[cfg(...)]` to skip it. This way the test is still compiled on all configurations — catching type errors and regressions early — but simply skipped at runtime.
 
 Use `#[cfg]` on tests **only** when the code cannot compile under the condition — for example, when the test references types, functions, or trait methods that are gated behind `#[cfg]` and do not exist on other platforms or feature sets.
 
@@ -231,16 +231,6 @@ fn unix_path_logic() { /* uses hardcoded unix paths but no unix-only types */ }
 #[cfg(unix)]
 #[test]
 fn block_size() { /* uses GetBlockSize which only exists on unix */ }
-
-// Good — test compiles with the flag, skipped at runtime
-#[test]
-#[cfg_attr(pdu_test_skip_some_test, ignore = "pdu_test_skip_some_test is set")]
-fn some_test() { /* ... */ }
-
-// Bad — excludes the test from compilation entirely when it could still compile
-#[cfg(not(pdu_test_skip_some_test))]
-#[test]
-fn some_test() { /* ... */ }
 ```
 
 ### Using `pipe-trait`
@@ -380,4 +370,4 @@ FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh
 > Always run the full test suite before committing, even for seemingly trivial changes such as documentation edits, comment changes, or config updates. Any change can break formatting, linting, building, tests, or doc generation across the different feature combinations.
 
 > [!NOTE]
-> Some tests may fail with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*` flags. Follow the hint and rerun with the suggested flags.
+> Some tests may fail with a hint about `TEST_SKIP`. Follow the hint and rerun with the suggested variable.

Cargo.toml

@@ -91,6 +91,3 @@ maplit = "1.0.2"
 normalize-path = "0.2.1"
 pretty_assertions = "1.4.1"
 rand = "0.10.0"
-
-[lints.rust]
-unexpected_cfgs = { level = "warn", check-cfg = ['cfg(pdu_test_skip_fs_errors)'] }

README.md

@@ -93,6 +93,7 @@ Environment Variables
 | `TEST`        | `true` or `false` | `true`        | Whether to run `cargo test`                     |
 | `BUILD_FLAGS` | string            | _(empty)_     | Space-separated list of flags for `cargo build` |
 | `TEST_FLAGS`  | string            | _(empty)_     | Space-separated list of flags for `cargo test`  |
+| `TEST_SKIP`   | string            | _(empty)_     | Space-separated list of test names to skip      |
 
 </details>
 

template/ai-instructions/shared.md

@@ -16,6 +16,6 @@ Read and follow the CONTRIBUTING.md file in this repository for all code style c
 - Minimize `unwrap()` in non-test code — use proper error handling
 - Prefer `#[cfg_attr(..., ignore = "reason")]` over `#[cfg(...)]` to skip tests — use `#[cfg]` on tests only when the code cannot compile under the condition (e.g., references types/functions that don't exist on other platforms)
 - Install toolchain before running tests: `rustup toolchain install "$(< rust-toolchain)" && rustup component add --toolchain "$(< rust-toolchain)" rustfmt clippy`
-- Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*`, follow the hint and rerun with the suggested flags.
+- Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `TEST_SKIP`, follow the hint and rerun with the suggested variable.
 - **ALWAYS run the full test suite** (`FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh`) before committing, regardless of how trivial the change seems — this includes documentation-only changes, comment edits, config changes, and refactors. The test suite checks formatting, linting, building, tests, and docs across multiple feature combinations; any type of change can break any of these checks.
 - Set `PDU_NO_FAIL_FAST=true` to run all checks instead of stopping at the first failure — this lets you see which checks pass and which fail

test.sh

@@ -56,10 +56,19 @@ run_if() (
 unit() (
   read -ra build_flags <<<"${BUILD_FLAGS:-}"
   read -ra test_flags <<<"${TEST_FLAGS:-}"
+  read -ra test_skip <<<"${TEST_SKIP:-}"
+  skip_args=()
+  for name in ${test_skip[@]+"${test_skip[@]}"}; do
+    skip_args+=(--skip "$name")
+  done
   run_if "${LINT:-true}" cargo clippy "$@" -- -D warnings
   run_if "${DOC:-false}" cargo doc "$@"
   run_if "${BUILD:-true}" cargo build ${build_flags[@]+"${build_flags[@]}"} "$@"
-  run_if "${TEST:-true}" cargo test ${test_flags[@]+"${test_flags[@]}"} "$@"
+  if [[ ${#skip_args[@]} -gt 0 ]]; then
+    run_if "${TEST:-true}" cargo test ${test_flags[@]+"${test_flags[@]}"} "$@" -- "${skip_args[@]}"
+  else
+    run_if "${TEST:-true}" cargo test ${test_flags[@]+"${test_flags[@]}"} "$@"
+  fi
 )
 
 run_if "${FMT:-true}" cargo fmt -- --check

tests/cli_errors.rs

@@ -107,13 +107,12 @@ fn max_depth_0() {
 
 #[cfg(unix)]
 #[test]
-#[cfg_attr(pdu_test_skip_fs_errors, ignore = "pdu_test_skip_fs_errors is set")]
 fn fs_errors() {
     if unsafe { libc::geteuid() } == 0 {
         panic!(
             "{}\n{}",
             "error: This test must not be run as root because running with elevated privileges would affect its accuracy.",
-            "hint: Either run this test as a non-root user or set `RUSTFLAGS='--cfg pdu_test_skip_fs_errors'` to skip this test.",
+            "hint: Either run this test as a non-root user or rerun via `TEST_SKIP='fs_errors' ./test.sh` to skip this test.",
         );
     }