pkg/eval: Fix test on BSD.

pkg/eval/exception_unix_test.go

@@ -4,6 +4,7 @@ package eval
 
 import (
 	"fmt"
+	"runtime"
 	"syscall"
 	"testing"
 
@@ -21,6 +22,9 @@ func TestExternalCmdExit_Error(t *testing.T) {
 		tt.Args(ExternalCmdExit{0x82, "ls", 1}).Rets("ls killed by signal interrupt (core dumped)"),
 		// 0x7f + signal<<8 for stopped
 		tt.Args(ExternalCmdExit{0x27f, "ls", 1}).Rets("ls stopped by signal interrupt (pid=1)"),
+	})
+	if runtime.GOOS == "linux" {
+		tt.Test(t, tt.Fn("Error", error.Error), tt.Table{
 			// 0x057f + cause<<16 for trapped. SIGTRAP is 5 on all Unix'es but have
 			// different string representations on different OSes.
 			tt.Args(ExternalCmdExit{0x1057f, "ls", 1}).Rets(fmt.Sprintf(
@@ -28,4 +32,5 @@ func TestExternalCmdExit_Error(t *testing.T) {
 			// 0xff is the only exit code that is not exited, signaled or stopped.
 			tt.Args(ExternalCmdExit{0xff, "ls", 1}).Rets("ls has unknown WaitStatus 255"),
 		})
+	}
 }