In this four-session software design challenge, Francesco Cirillo shows how to develop a real use case by interacting with different APIs of various services.

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Challenge Content

This Challenge is organized in four sessions.

SESSION 01 - INTERACTING WITH THE FIRST API IN TDD

Interacting with an online service through its APIs.

• Presentation of the User Stories, Scenarios and Requirements.
• Definition of criteria to evaluate the effectiveness of software design.
• Development of the software feature to retrieve orders for a certain group of "products" on the online store.
• Assessment of alternative and exceptional cases.
• Generate a simple list of booked dates.

Session 02 - NEW ABSTRACTIONS EMERGE TO DEAL WITH THE SECOND API

Finding abstractions that enable access more than one API

• Spike: Accessing the Google Calendar.
• Spike: Create new events.
• Spike: Do events already exist?
• Dynamic differences and similarities in connection interactions.
• Dynamic differences and similarities in communication interactions.
• Connect and communicate with the second API in TDD with the objects of the first API.
• Evaluation assessment of the current software design.

Session 03 - NEW POWERFUL ABSTRACTIONS EMERGE TO DEAL WITH THE THIRD API

Is the software system becoming simpler?

• Spike: Send emails via an online API.
• Spike: Send emails programmatically.
• Spike: Has the email been opened?
• Dynamic differences and similarities in connection interactions.
• Dynamic differences and similarities in communication interactions.
• Send emails to the attendants of Mentoring sessions!!
• Evaluation of the current software design.

Session 04 - VALIDATION AND EXCEPTIONAL FLOWS TO SIMPLIFY OUR DESIGN

Making the use case workflow simple.

• Make a list of alternative and exceptional cases.
• Differences and similarities between the various services.
• Develop some exceptional cases in TDD.
• Evaluation of the result.

About this Challenge

The Working with APIs Challenge is a Course where Francesco Cirillo develops a feature to improve his back office Mentoring service.

In order to do this, the software needs to interact with several external systems via their APIs: Francesco’s Online Store, a specific Google Calendar, a Google Sheet and an EmailManager APIs.

Objectives

As a result of this course, you will learn to:

The Story Behind this Challenge

This challenge stems from a real situation. For a few months, I worked in a start-up. Their product was very simple. The system retrieves input data from a number of external systems through their APIs, applies rules, performs calculations and sends its output to other systems through their APIs. Basically, a simple IPO (Input Process Output) with the use of APIs.

From a business point of view, expanding the startup meant accepting new and different external systems to retrieve data from and possibly new external systems to send data to.

But it that start-up, accepting any new external system meant writing a new module from scratch:

• The code to connect and be authorized by the external system.
• The code to interact with the external system via API.
• The code to validate the information received from that system.
• The code necessary to deal with exceptional flows that could happen in the interaction with that system.

This happened not only for two seemingly different system APIs, for example, an online payment service and an online store. But it also happened for two similar external systems (two payment services).

Consequences

As the business expanded:

• The number of lines of code grew
• The complexity of lines of code grew over time.
• The number of bugs increased.
• The time to deliver the functionality increased (indefinitely=never ending stories).
• A demand to hire more developers increased.
• The need to divide up the work in a specialised way (waterfall style) grew.

Poor software system!

You might argue...

“Francesco, the API of every external system offers a different way to interact! APIs are different, shouldn't we handle them as necessary?”

Francesco’s short answer: "NO!"

What's the benefit of software design?

The idea behind software design is to find a number of objects that can be put together in order to develop ALL the interactions with very different APIs of any possible external system!

It is possible to apply the same reasoning to validation and exception handling.

What are the consequences now that software design is applied?

Consequences (@GoodDesign)

As the business develops:

• The number of lines of code is stable or decreases.
• The software system becomes simpler over time.
• The number of bugs decreases.
• Time to deliver functionality decreases and becomes more predictable (> Flatten the curve<)
• There is no need to hire new developers.
• Developers can work in a despecialised manner.

Ready to program?

About the Trainer

Francesco Cirillo

Francesco Cirillo has worked at the forefront of the software industry for more than 30 years. In a career spanning startups, corporations and freelance consulting, he has mentored thousands of professionals, developers, managers and software teams.

In the 1990s he worked as a Senior Consultant and Mentor for Sun Microsystem, expert in Software Architectures and Software Development Processes and Java and Object-Oriented Evangelist.

Francesco is one of the pioneers of Agile Methods. He started working on XP and TDD in 1999. He was chosen by Kent Beck to develop the XP community in Europe and as reviewer of the second edition of the book Extreme Programming Explained. In 2000 he created XPLabs, the first company in Europe to offer comprehensive services on XP: software development, training and consulting.

In 2007 he created the Anti-IF Campaign to raise awareness in the international community of software developers to apply good design principles to grow software in a sustainable way.

Since 2008 Francesco stopped actively working on Agile Methods and started to develop RRP, a new method of software development. In 2013 he created Cirillo Consulting based in Berlin to offer professional training and consulting on productivity and software development.

Francesco invented the Pomodoro® Technique, a renowned time-management method used by millions of people all over the world, while being a university student looking for a way to get more done in less time.

Read the Francesco Cirillo's complete profile.

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