Mastering Vertical Slicing: The Cornerstone of Agile Development
Published: 2023-10-23 15:30:20


In the dynamic realm of software development, agility and efficiency are paramount. To maximize these qualities, a practice known as "vertical slicing" has emerged as a game-changing strategy. Instead of approaching projects in a horizontal manner, where each layer of the software stack is developed separately, vertical slicing encourages developers to focus on one feature at a time, building all the necessary components from top to bottom. In this blog post, we'll delve into the concept of vertical slices and explore its significance in the world of agile software development.

## Understanding Vertical Slicing

Visualize your software project as a grid, with desired features listed in columns and different layers of the software stack in rows. This grid may encompass items such as migrations, models, seed data, controller actions, view logic, data fetching, and styling. Each feature, represented as a column, is treated as a vertical slice that traverses all architectural layers to deliver visible value to the end user.

##Why Story Splitting Matters

Breaking down a project into prioritized, small user stories is essential for agile teams. However, many teams struggle to divide extensive user stories into more manageable units. Instead of achieving small vertical slices that cut through their architecture, they end up with stories that resemble tasks or architectural components. This approach falls short of delivering the value or feedback that small stories should provide.

Fortunately, the skill of story splitting can be acquired relatively quickly, significantly enhancing a team's efficiency and agility. Let's explore what constitutes a good user story and how it aligns with the concept of vertical slicing.

## What Makes a Good User Story?

Before delving into story splitting, it's imperative to understand the elements of a good user story. At its core, a user story is a description of a change in system behavior from the user's perspective. It outlines something a user wants to accomplish with the system or something they expect the system to do for them, which it currently does not.

User stories are typically structured as follows:

As a [role], I want [action or feature] so that [value or goal].
This format aids in addressing three essential questions:

Who is the intended user?
What do they want to achieve or have the system do?
Why do they want this?
While this template is valuable, it is not always necessary to use it in its entirety. A concise title, supported by additional context, can often suffice. The goal is to maintain a focus on the user's perspective throughout the development process.

## INVEST in Good User Stories

Bill Wake introduced the INVEST acronym to highlight six crucial attributes of good user stories:

Independent
Negotiable
Valuable
Estimable
Small
Testable
These attributes guide the creation of effective user stories. For instance, stories should be independent, meaning they can be prioritized without relying on technical dependencies. They should also be negotiable, allowing room for collaboration on details. Additionally, stories must deliver visible value to users, be estimable in terms of effort, small enough to fit into a sprint, and testable to determine when they are complete.

## User Stories Are Vertical Slices

The term "vertical slice" is closely associated with good user stories. A vertical slice represents a work item that delivers a valuable change in system behavior, necessitating adjustments across multiple architectural layers. When a vertical slice is completed, the system becomes observably more valuable to users.

In contrast, a horizontal slice refers to a work item that concentrates on changes to a single component or architectural layer. Such slices must be combined with changes in other layers to provide observable value to users.

To achieve most of the INVEST attributes, a story often needs to touch all three core architectural layers: the UI, business logic, and the database. This is why a story is considered a vertical slice through the system.

## Benefits of Working with Vertical Slices

When teams embrace vertical slicing, several advantages emerge:

Explicit Value: The backlog reflects the value delivered to users, making it easier to prioritize and plan.

Value-Centric Conversations: Teams engage in more discussions about the value of features, fostering a deeper understanding.

Reduced Low-Value Work: Vertical slices discourage the development of low-value changes or unnecessary features.

Faster Value Delivery: Teams deliver value sooner in the development process.

High-Quality Feedback: Early feedback ensures higher-quality results.

Improved Visibility: Constraints and inventory become more visible, allowing teams to respond effectively.

Predictability: Working software becomes the primary measure of progress, enhancing predictability.

## In Conclusion:

In the ever-evolving landscape of software development, the concept of vertical slicing has proven to be a powerful strategy for building agile, efficient, and value-driven software. By focusing on delivering small, valuable, and testable user stories that cut across architectural layers, development teams can maximize their productivity, respond to user needs more effectively, and ultimately deliver high-quality software that meets customer expectations. So, the next time you embark on a software project, consider adopting the vertical slicing approach to enhance your development process.