test: Skip TestOptions_FS when not using CopyBytes

The only `FileCopyMethod` that supports this is CopyBytes.

Author: eth-p

all_test.go

@@ -431,6 +431,10 @@ func TestOptions_OnFileError(t *testing.T) {
 }
 
 func TestOptions_FS(t *testing.T) {
+	if defaultCopyMethodName != "CopyBytes" {
+		t.Skipf("Can only test FS reading with CopyBytes method, not %s", defaultCopyMethodName)
+	}
+
 	os.RemoveAll("test/data/case18/assets")
 	err := Copy("test/data/case18/assets", "test/data.copy/case18/assets", Options{
 		FS:                assets,