tests: factor out utility function is_external_tool_installed

A pattern has emerged where a integration tests check for the
availability of an external tool (`git`, `taplo`, `gpg`, ...) and skip
the test (by simply passing it) when it is not available. To check this,
the program is run with the `--version` flag.

Some tests require that the program be available at least when running
in CI, by calling `ensure_running_outside_ci` conditionally on the
outcome. The decision is up to each test, though, the utility merely
returns a `bool`.

cli/tests/test_config_schema.rs

@@ -4,14 +4,10 @@ use std::process::Output;
 use std::process::Stdio;
 
 use testutils::ensure_running_outside_ci;
+use testutils::is_external_tool_installed;
 
 fn taplo_check_config(file: &Path) -> datatest_stable::Result<Option<Output>> {
-    if Command::new("taplo")
+    if !is_external_tool_installed("taplo") {
-        .arg("--version")
-        .stdout(Stdio::null())
-        .status()
-        .is_err()
-    {
         ensure_running_outside_ci("`taplo` must be in the PATH");
         eprintln!("Skipping test because taplo is not installed on the system");
         return Ok(None);

lib/tests/test_git_backend.rs

@@ -15,7 +15,6 @@
 use std::collections::HashMap;
 use std::collections::HashSet;
 use std::path::Path;
-use std::process::Command;
 use std::sync::Arc;
 use std::time::Duration;
 use std::time::SystemTime;
@@ -39,6 +38,7 @@ use testutils::commit_with_tree;
 use testutils::create_random_commit;
 use testutils::create_single_tree;
 use testutils::create_tree;
+use testutils::is_external_tool_installed;
 use testutils::repo_path;
 use testutils::repo_path_buf;
 use testutils::CommitGraphBuilder;
@@ -96,7 +96,7 @@ fn make_commit(
 #[test]
 fn test_gc() {
     // TODO: Better way to disable the test if git command couldn't be executed
-    if Command::new("git").arg("--version").status().is_err() {
+    if !is_external_tool_installed("git") {
         eprintln!("Skipping because git command might fail to run");
         return;
     }

lib/tests/test_gpg.rs

@@ -3,7 +3,6 @@ use std::fs::Permissions;
 use std::io::Write as _;
 #[cfg(unix)]
 use std::os::unix::prelude::PermissionsExt as _;
-use std::process::Command;
 use std::process::Stdio;
 
 use assert_matches::assert_matches;
@@ -14,6 +13,7 @@ use jj_lib::signing::SigStatus;
 use jj_lib::signing::SignError;
 use jj_lib::signing::SigningBackend as _;
 use testutils::ensure_running_outside_ci;
+use testutils::is_external_tool_installed;
 
 static GPG_PRIVATE_KEY: &str = r#"-----BEGIN PGP PRIVATE KEY BLOCK-----
 
@@ -165,7 +165,7 @@ impl GpgsmEnvironment {
 
 macro_rules! gpg_guard {
     () => {
-        if Command::new("gpg").arg("--version").status().is_err() {
+        if !is_external_tool_installed("gpg") {
             ensure_running_outside_ci("`gpg` must be in the PATH");
             eprintln!("Skipping test because gpg is not installed on the system");
             return;
@@ -175,7 +175,7 @@ macro_rules! gpg_guard {
 
 macro_rules! gpgsm_guard {
     () => {
-        if Command::new("gpgsm").arg("--version").status().is_err() {
+        if !is_external_tool_installed("gpgsm") {
             ensure_running_outside_ci("`gpgsm` must be in the PATH");
             eprintln!("Skipping test because gpgsm is not installed on the system");
             return;

lib/testutils/src/lib.rs

@@ -15,6 +15,7 @@
 use std::collections::HashMap;
 use std::collections::HashSet;
 use std::env;
+use std::ffi::OsStr;
 use std::fs;
 use std::fs::OpenOptions;
 use std::io::Read as _;
@@ -142,6 +143,15 @@ pub fn ensure_running_outside_ci(reason: &str) {
     assert!(!running_in_ci, "Running in CI, {reason}.");
 }
 
+/// Tests if an external tool is installed and in the PATH
+pub fn is_external_tool_installed(program_name: impl AsRef<OsStr>) -> bool {
+    Command::new(program_name)
+        .arg("--version")
+        .stdout(Stdio::null())
+        .status()
+        .is_ok()
+}
+
 #[derive(Debug)]
 pub struct TestEnvironment {
     temp_dir: TempDir,
@@ -627,12 +637,7 @@ pub fn assert_abandoned_with_parent(
 pub fn assert_no_forgotten_test_files(test_dir: &Path) {
     // We require `taplo` for this check; if it's not installed, that's ok unless
     // we're running in CI.
-    if Command::new("taplo")
+    if !is_external_tool_installed("taplo") {
-        .arg("--version")
-        .stdout(Stdio::null())
-        .status()
-        .is_err()
-    {
         ensure_running_outside_ci("`taplo` must be in the PATH");
         eprintln!(
             "Skipping check for forgotten test files because taplo is not installed on the system"