// Given
        byte[] capturedFileId = new byte[1];
        RequestWithFileId anonymousImpl = new RequestWithFileId() {
            private byte[] fileId;

            @Override
            public void setFileId(byte[] fileId) {
                this.fileId = fileId;
                if (fileId != null) {
                    capturedFileId[0] = fileId[0];
                }
            }