I have been writing unit tests using mockito framework.
I have this below legacy code, how do I mock the RemoteService client object in the approvalAction method without refactoring it?

```
public Map<String, String> approvalAction(long documentId, ActionCommandDTO request, FormData formData, byte[] prevData) {

    RemoteService client = getRemoteService();
    String urlString = String.format("formExtensions/%s?%s", formData.getId(), getAuthParam(formData.getRealm()));
    try {
        response = client.postEntity(urlString, String.class, approvalSvcRequestStr);
    } catch (Exception e) {
        // TODO: handle rollback properly for P2P
        handleApprovalActionFailed(documentId, request, formData, prevData);
    }

    return map;
}

private RemoteService getRemoteService() {

    RemoteServiceConfig remoteServiceConfig = (RemoteServiceConfig) this.serviceConfigRegistry.getServiceConfigs().get("approval");
    remoteServiceConfig.setClientID(clientId);
    remoteServiceConfig.setClientSecret(privateSecret);
    RemoteService remoteService = new RemoteService(remoteServiceConfig, authorizationHeaderServiceImpl);

    return remoteService;
}

```