func TestCallbacks(t *testing.T) {
	type callback struct {
		name    string
		before  string
		after   string
		remove  bool
		replace bool
		err     string
		match   func(*gorm.DB) bool
		h       func(*gorm.DB)
	}

	datas := []struct {
		callbacks []callback
		err       string
		results   []string
	}{
		{
			callbacks: []callback{{h: c1}, {h: c2}, {h: c3}, {h: c4}, {h: c5}},

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

            projectsConfigured(":buildSrc", ":b")
            buildModelCreated()
            modelsCreated(":", ":a")
        }

        outputContains("Callback before root project 'root'")
        outputContains("Callback before project ':a'")
        outputContains("Callback before project ':b'")


        when:
        withIsolatedProjects()
        def model2 = runBuildAction(new FetchCustomModelForEachProject())

    boolean ran = false;
    @Nullable Callback callback = null;

    public SimpleTearDown() {}

    public SimpleTearDown(Callback callback) {
      this.callback = callback;
    }

    @Override
    public void tearDown() throws Exception {
      if (callback != null) {
        callback.run();
      }
      ran = true;
    }
  }

  override fun handle(callbacks: Array<Callback>) {
    for (callback in callbacks) {
      if (callback is PasswordCallback) {
        val console = System.console()

        if (console != null) {
          callback.password = console.readPassword(callback.prompt)
        } else {
          System.err.println(callback.prompt)
          callback.password = System.`in`.bufferedReader().readLine().toCharArray()

)

// Controller watches a ConfigMap and calls the given callback when the ConfigMap changes.
// The ConfigMap is passed to the callback, or nil if it doesn't exist.
type Controller struct {
	configmaps kclient.Client[*v1.ConfigMap]
	queue      controllers.Queue

	configMapNamespace string
	configMapName      string
	callback           func(*v1.ConfigMap)

	hasSynced atomic.Bool
}

	createCallback.Clauses = config.CreateClauses

	queryCallback := db.Callback().Query()
	queryCallback.Register("gorm:query", Query)
	queryCallback.Register("gorm:preload", Preload)
	queryCallback.Register("gorm:after_query", AfterQuery)
	queryCallback.Clauses = config.QueryClauses

	deleteCallback := db.Callback().Delete()
	deleteCallback.Match(enableTransaction).Register("gorm:begin_transaction", BeginTransaction)

// license that can be found in the LICENSE file.

class Callback {
public:
	virtual ~Callback() { }
	virtual std::string run() { return "Callback::run"; }
};

class Caller {
private:
	Callback *callback_;
public:
	Caller(): callback_(0) { }
	~Caller() { delCallback(); }
	void delCallback() { delete callback_; callback_ = 0; }
	void setCallback(Callback *cb) { delCallback(); callback_ = cb; }
	std::string call();

    void cancel();

    /**
     * @return current state of cancellation request before callback was added.
     */
    boolean addCallback(Runnable cancellationHandler);

    /**
     * Removes a callback called when cancellation request happens.
     *
     * @param cancellationHandler removed callback.
     */
    void removeCallback(Runnable cancellationHandler);

            String json = builder.endArray()
                .endObject()
                .endArray()
                .endObject()
                .endObject().string();
            if(callback != null && callback.length > 0) {
                json = callback[0] + '(' + json + ')';
            }
            return ok(json);
        } catch (Exception e) {
            return internalServerError(e.getMessage());
        }
    }