additional lock file test

Author: skarim

internal/stack/lock.go

@@ -21,14 +21,14 @@ func (e *LockError) Unwrap() error { return e.Err }
 
 // LockTimeout is how long Lock() will wait for the exclusive lock before
 // giving up.  With the lock held only during file writes (milliseconds),
-// this timeout primarily guards against stuck or orphaned lock files.
+// this timeout primarily guards against a hung process holding the lock.
 const LockTimeout = 5 * time.Second
 
 // lockRetryInterval is the sleep between non-blocking lock attempts.
 const lockRetryInterval = 100 * time.Millisecond
 
 // FileLock provides an exclusive advisory lock on the stack file to prevent
-// concurrent Load-Modify-Save races between multiple gh-stack processes.
+// concurrent writes between multiple gh-stack processes.
 type FileLock struct {
 	f *os.File
 }

internal/stack/lock_test.go

@@ -2,6 +2,8 @@ package stack
 
 import (
 	"fmt"
+	"os"
+	"path/filepath"
 	"sync"
 	"testing"
 	"time"
@@ -123,6 +125,9 @@ func TestLock_FileLeftOnDisk(t *testing.T) {
 	lock.Unlock()
 
 	// Lock file should still exist after unlock (no os.Remove race).
+	_, err = os.Stat(filepath.Join(dir, lockFileName))
+	require.NoError(t, err, "lock file should remain on disk after unlock")
+
 	lock2, err := Lock(dir)
 	require.NoError(t, err, "should be able to re-lock after unlock")
 	lock2.Unlock()