Replace deprecated cargo_bin with cargo_bin! macro (#579)

The `assert_cmd::cargo::cargo_bin()` function relies on Cargo's internal
directory structure to locate test binaries. This breaks when
`CARGO_BUILD_BUILD_DIR` is set, and will fail with upcoming Cargo
changes (rust-lang/cargo#16147, rust-lang/cargo#15010).

Author: Copilot

tests/integration_util/mod.rs

@@ -0,0 +1,42 @@
+// Copyright 2024 Martin Pool
+
+//! Utilities specific to integration tests that need access to the binary under test.
+
+use std::env;
+
+/// Create a Command to run cargo-mutants for integration tests.
+pub fn run() -> assert_cmd::Command {
+    let mut cmd = assert_cmd::Command::new(assert_cmd::cargo_bin!("cargo-mutants"));
+    // Strip any options configured in the environment running these tests,
+    // so that they don't cause unexpected behavior in the code under test.
+    //
+    // For example, without this,
+    // `env CARGO_MUTANTS_JOBS=4 cargo mutants`
+    //
+    // would end up with tests running 4 jobs by default, which would cause
+    // the tests to fail.
+    //
+    // Even more generally than that example, we want the tests to be as hermetic
+    // as reasonably possible.
+    //
+    // Also strip GITHUB_ACTION to avoid automatically emitting github annotations,
+    // so that tests are more hermetic and reproducible between local and CI.
+    env::vars()
+        .map(|(k, _v)| k)
+        .filter(|k| {
+            k.starts_with("CARGO_MUTANTS_")
+                || k == "CLICOLOR_FORCE"
+                || k == "NOCOLOR"
+                || k == "CARGO_TERM_COLOR"
+                || k == "GITHUB_ACTION"
+        })
+        .for_each(|k| {
+            cmd.env_remove(k);
+        });
+    cmd
+}
+
+/// Returns the path to the cargo-mutants binary under test.
+pub fn main_binary() -> &'static std::path::Path {
+    assert_cmd::cargo_bin!("cargo-mutants")
+}

tests/main.rs

@@ -21,10 +21,12 @@ use serde_json::json;
 use similar::TextDiff;
 use tempfile::{tempdir, NamedTempFile, TempDir};
 
+mod integration_util;
 mod util;
+use integration_util::run;
 use util::{
-    assert_bytes_eq_json, copy_of_testdata, copy_testdata_to, outcome_json_counts, run,
-    CommandInstaExt, OUTER_TIMEOUT,
+    assert_bytes_eq_json, copy_of_testdata, copy_testdata_to, outcome_json_counts, CommandInstaExt,
+    OUTER_TIMEOUT,
 };
 
 #[test]
@@ -1413,7 +1415,7 @@ fn interrupt_caught_and_kills_children() {
     use nix::sys::signal::{kill, SIGTERM};
     use nix::unistd::Pid;
 
-    use crate::util::MAIN_BINARY;
+    use crate::integration_util::main_binary;
 
     let tmp_src_dir = copy_of_testdata("well_tested");
     // We can't use `assert_cmd` `timeout` here because that sends the child a `SIGKILL`,
@@ -1426,7 +1428,7 @@ fn interrupt_caught_and_kills_children() {
     // Skip baseline because firstly it should already pass but more importantly
     // #333 exhibited only during non-baseline scenarios.
     let args = [
-        MAIN_BINARY.to_str().unwrap(),
+        main_binary().to_str().unwrap(),
         "mutants",
         "--timeout=300",
         "--baseline=skip",

tests/util/mod.rs

@@ -8,13 +8,11 @@
 //! cargo-mutants (as `use crate::test_util`).
 
 use std::borrow::Borrow;
-use std::env;
 use std::fs::{read_dir, read_to_string, rename};
-use std::path::{Path, PathBuf};
+use std::path::Path;
 use std::time::Duration;
 
 use itertools::Itertools;
-use lazy_static::lazy_static;
 use tempfile::TempDir;
 
 /// A timeout for a `cargo mutants` invocation from the test suite. Needs to be
@@ -23,41 +21,6 @@ use tempfile::TempDir;
 /// forever.
 pub const OUTER_TIMEOUT: Duration = Duration::from_secs(60);
 
-lazy_static! {
-    pub static ref MAIN_BINARY: PathBuf = assert_cmd::cargo::cargo_bin("cargo-mutants");
-}
-
-pub fn run() -> assert_cmd::Command {
-    let mut cmd = assert_cmd::Command::new(MAIN_BINARY.as_os_str());
-    // Strip any options configured in the environment running these tests,
-    // so that they don't cause unexpected behavior in the code under test.
-    //
-    // For example, without this,
-    // `env CARGO_MUTANTS_JOBS=4 cargo mutants`
-    //
-    // would end up with tests running 4 jobs by default, which would cause
-    // the tests to fail.
-    //
-    // Even more generally than that example, we want the tests to be as hermetic
-    // as reasonably possible.
-    //
-    // Also strip GITHUB_ACTION to avoid automatically emitting github annotations,
-    // so that tests are more hermetic and reproducible between local and CI.
-    env::vars()
-        .map(|(k, _v)| k)
-        .filter(|k| {
-            k.starts_with("CARGO_MUTANTS_")
-                || k == "CLICOLOR_FORCE"
-                || k == "NOCOLOR"
-                || k == "CARGO_TERM_COLOR"
-                || k == "GITHUB_ACTION"
-        })
-        .for_each(|k| {
-            cmd.env_remove(k);
-        });
-    cmd
-}
-
 pub trait CommandInstaExt {
     fn assert_insta(&mut self, snapshot_name: &str);
 }