From 2def946f04927a47a29a3cb90797f214ed96f050 Mon Sep 17 00:00:00 2001 From: Aleksey Kladov Date: Thu, 28 May 2020 18:56:55 +0200 Subject: [PATCH] Initial --- .gitignore | 2 + Cargo.toml | 12 +++ LICENSE-APACHE | 201 +++++++++++++++++++++++++++++++++++++++++++++++++ LICENSE-MIT | 23 ++++++ README.md | 21 ++++++ src/lib.rs | 177 +++++++++++++++++++++++++++++++++++++++++++ tests/smoke.rs | 13 ++++ 7 files changed, 449 insertions(+) create mode 100644 .gitignore create mode 100644 Cargo.toml create mode 100644 LICENSE-APACHE create mode 100644 LICENSE-MIT create mode 100644 README.md create mode 100644 src/lib.rs create mode 100644 tests/smoke.rs diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..96ef6c0 --- /dev/null +++ b/.gitignore @@ -0,0 +1,2 @@ +/target +Cargo.lock diff --git a/Cargo.toml b/Cargo.toml new file mode 100644 index 0000000..289ac25 --- /dev/null +++ b/Cargo.toml @@ -0,0 +1,12 @@ +[package] +name = "cov-mark" +version = "1.0.0" +authors = ["Aleksey Kladov "] +license = "MIT OR Apache-2.0" +edition = "2018" +description = "Manual coverage marks." +repository = "https://github.com/matklad/cov-mark" +documentation = "https://docs.rs/cov-mark" + +keywords = ["coverage", "test"] +categories = ["development-tools"] diff --git a/LICENSE-APACHE b/LICENSE-APACHE new file mode 100644 index 0000000..16fe87b --- /dev/null +++ b/LICENSE-APACHE @@ -0,0 +1,201 @@ + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + +TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + +1. 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IN NO EVENT +SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY +CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION +OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR +IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +DEALINGS IN THE SOFTWARE. diff --git a/README.md b/README.md new file mode 100644 index 0000000..81c1fce --- /dev/null +++ b/README.md @@ -0,0 +1,21 @@ +# cov-mark + +Verify that your tests exercise the conditions you think they are exercising + +```rust +fn safe_divide(dividend: u32, divisor: u32) -> u32 { + if divisor == 0 { + cov_mark::hit!(save_divide_zero); + return 0; + } + dividend / divisor +} + +#[test] +fn test_safe_divide_by_zero() { + cov_mark::check!(save_divide_zero); + assert_eq!(safe_divide(92, 0), 0); +} +``` + +See [the docs](https://docs.rs/cov-mark) for details diff --git a/src/lib.rs b/src/lib.rs new file mode 100644 index 0000000..94cd84d --- /dev/null +++ b/src/lib.rs @@ -0,0 +1,177 @@ +//! # cov-mark +//! +//! This library provides two macros, `cov_mark::hit!` and `cov_mark::check!`, +//! which can be used to verify that a certain test exercises a certain code +//! path. +//! +//! Here's a short example: +//! +//! ``` +//! fn parse_date(s: &str) -> Option<(u32, u32, u32)> { +//! if 10 != s.len() { +//! // By using `cov_mark::hit!` +//! // we signal which test exercises this code. +//! cov_mark::hit!(short_date); +//! return None; +//! } +//! +//! if "-" != &s[4..5] || "-" != &s[7..8] { +//! cov_mark::hit!(bad_dashes); +//! return None; +//! } +//! // ... +//! # unimplemented!() +//! } +//! +//! #[test] +//! fn test_parse_date() { +//! { +//! // `cov_mark::check!` creates a guard object +//! // that verifies that by the end of the scope we've +//! // executed the corresponding `cov_mark::hit`. +//! cov_mark::check!(short_date); +//! assert!(parse_date("92").is_none()); +//! } +//! +//! // This will fail. Although the test looks like +//! // it exercises the second condition, it does not. +//! // The call to `covers!` call catches this bug in the test. +//! // { +//! // cov_mark::check!(bad_dashes);; +//! // assert!(parse_date("27.2.2013").is_none()); +//! // } +//! +//! { +//! cov_mark::check!(bad_dashes); +//! assert!(parse_date("27.02.2013").is_none()); +//! } +//! } +//! +//! # fn main() {} +//! ``` +//! +//! Here's why coverage marks are useful: +//! +//! * Verifying that something doesn't happen for the *right* reason. +//! * Finding the test that exercises the code (grep for `check!(mark_name)`). +//! * Finding the code that the test is supposed to check (grep for `hit!(mark_name)`). +//! * Making sure that code and tests don't diverge during refactorings. +//! * (If used pervasively) Verifying that each branch has a corresponding test. +//! +//! # Limitations +//! +//! * In the presence of threads, `cov_mark::check!` may falsely pass, if the +//! mark is hit by an unrelated thread. +//! * Names of marks must be globally unique. +//! * `cov_mark::check!` can't be used in integration tests. +//! +//! # Implementation Details +//! +//! Each coverage mark is an `AtomicUsize` counter. `cov_mark::hit!` increments +//! this counter, `cov_mark::check!` returns a guard object which checks that +//! the mark was incremented. +//! +//! Counters are declared using `#[no_mangle]` attribute, so that `hit!` and +//! `cover!` both can find the mark without the need to declare it in a common +//! module. Aren't the linkers ~~horrible~~ wonderful? +//! +//! # Safety +//! +//! Technically, the `hit!` macro in this crate is unsound: it uses `extern "C" +//! #[no_mangle]` symbol, which *could* clash with an existing symbol and cause +//! UB. For example, `cov_mark::hit!(main)` may segfault. That said: +//! +//! * If there's no existing symbol, the result is a linker error. +//! * If there exists corresponding `cov_mark::check!`, the result is a linker +//! error. +//! * Code inside `cov_mark::hit!` is hidden under `#[cfg(test)]`. +//! +//! It is believed that it is practically impossible to cause UB by accident +//! when using this crate. For this reason, the `hit` macro hides unsafety +//! inside. + +/// Hit a mark with a specified name. +/// +/// # Example +/// +/// ``` +/// fn safe_divide(dividend: u32, divisor: u32) -> u32 { +/// if divisor == 0 { +/// cov_mark::hit!(save_divide_zero); +/// return 0; +/// } +/// dividend / divisor +/// } +/// ``` +#[macro_export] +macro_rules! hit { + ($ident:ident) => {{ + #[cfg(test)] + { + extern "C" { + #[no_mangle] + static $ident: $crate::__rt::AtomicUsize; + } + unsafe { + $ident.fetch_add(1, $crate::__rt::Ordering::Relaxed); + } + } + }}; +} + +/// Checks that a specified mark was hit. +/// +/// # Example +/// +/// ``` +/// #[test] +/// fn test_safe_divide_by_zero() { +/// cov_mark::check!(save_divide_zero); +/// assert_eq!(safe_divide(92, 0), 0); +/// } +/// # fn safe_divide(dividend: u32, divisor: u32) -> u32 { +/// # if divisor == 0 { +/// # cov_mark::hit!(save_divide_zero); +/// # return 0; +/// # } +/// # dividend / divisor +/// # } +/// ``` +#[macro_export] +macro_rules! check { + ($ident:ident) => { + #[no_mangle] + static $ident: $crate::__rt::AtomicUsize = $crate::__rt::AtomicUsize::new(0); + let _guard = $crate::__rt::Guard::new(&$ident); + }; +} + +#[doc(hidden)] +pub mod __rt { + pub use std::sync::atomic::{AtomicUsize, Ordering}; + + pub struct Guard { + mark: &'static AtomicUsize, + value_on_entry: usize, + } + + impl Guard { + pub fn new(mark: &'static AtomicUsize) -> Guard { + let value_on_entry = mark.load(Ordering::Relaxed); + Guard { + mark, + value_on_entry, + } + } + } + + impl Drop for Guard { + fn drop(&mut self) { + if std::thread::panicking() { + return; + } + let value_on_exit = self.mark.load(Ordering::Relaxed); + assert!(value_on_exit > self.value_on_entry, "mark was not hit") + } + } +} diff --git a/tests/smoke.rs b/tests/smoke.rs new file mode 100644 index 0000000..ec0535e --- /dev/null +++ b/tests/smoke.rs @@ -0,0 +1,13 @@ +fn safe_divide(dividend: u32, divisor: u32) -> u32 { + if divisor == 0 { + cov_mark::hit!(save_divide_zero); + return 0; + } + dividend / divisor +} + +#[test] +fn test_safe_divide_by_zero() { + cov_mark::check!(save_divide_zero); + assert_eq!(safe_divide(92, 0), 0); +}