all: optionally forbid degrading in tests

This enables transparently degradable tests to be forced on in environments known to support them.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/acl/acl_test.go

@@ -11,9 +11,11 @@ import (
 	"path/filepath"
 	"reflect"
 	"strconv"
+	"syscall"
 	"testing"
 
 	"hakurei.app/internal/acl"
+	"hakurei.app/internal/info"
 )
 
 const testFileName = "acl.test"
@@ -24,8 +26,14 @@ var (
 )
 
 func TestUpdate(t *testing.T) {
-	if os.Getenv("HAKUREI_TEST_SKIP_ACL") == "1" {
-		t.Skip("acl test skipped")
+	if info.CanDegrade {
+		name := filepath.Join(t.TempDir(), "check-degrade")
+		if err := os.WriteFile(name, nil, 0); err != nil {
+			t.Fatal(err)
+		}
+		if err := acl.Update(name, os.Geteuid()); errors.Is(err, syscall.ENOTSUP) {
+			t.Skip(err)
+		}
 	}
 
 	testFilePath := filepath.Join(t.TempDir(), testFileName)