Understanding CI/CD: Continuous Integration, Delivery, and Deployment

CI/CD has changed the way developers and testers release software. This first article in a series describes the shift and provides explanations of various tools and processes to help developers better use CI/CD.

From the original waterfall model to agile development and today’s DevOps, this is the technical path modern developers follow to build outstanding products. With the rise of DevOps, continuous integration, continuous delivery (CI/CD), and continuous deployment have emerged, making traditional software development and delivery methods quickly obsolete.

In the past agile era, most companies released software monthly, quarterly, or even yearly, but in the DevOps era weekly, daily, or multiple times per day is normal, especially for SaaS where updates can be delivered dynamically without users noticing.

Development teams use software delivery pipelines to automate and shorten delivery cycles, with most teams having automated processes to check code and deploy to new environments. This article introduces what CI/CD/CD is and how modern software companies automate code deployment.

Continuous Integration (CI) focuses on merging developers’ work into a single code repository, often several times a day, to discover integration errors early and improve team collaboration. Continuous Delivery (CD) aims to minimize friction in deployment by automating each step so code can be safely released at any time. Continuous Deployment extends automation further, automatically building and deploying code whenever changes pass all tests.

All these stages are parts of a delivery pipeline. Humble and Ferley explain in their book *Continuous Delivery* that every software change goes through a complex process involving multiple testing and deployment stages, requiring cooperation across many teams.

Continuous Integration (CI)

Through CI, developers frequently integrate code into the main branch of a shared repository, allowing multiple submissions at any time instead of waiting for the end of a development cycle.

The key idea is to enable faster, more frequent integration, reducing merge conflicts and their cost. While CI does not guarantee additional quality, many organizations find it increases overhead because they rely on manual checks to prevent new bugs. To reduce friction, CI depends on test suites and automation, though automated testing differs from continuous testing, which will be explained later.

CI’s goal is to make integration a simple, repeatable daily task, lowering overall build costs and catching defects early. Effective CI requires a shift in team habits toward frequent iterative builds and early bug resolution.

Continuous Delivery (CD)

CD expands CI by further automating the software delivery process so that code can be easily deployed to production environments at any time. A mature CD setup maintains a continuously deployable codebase, turning releases into routine, low‑stress events that can happen anytime during development.

CD relies heavily on deployment pipelines that automate testing and deployment. These pipelines execute progressive test suites for each build and are highly automated, often easy to configure in cloud environments.

If a build fails a critical test, the pipeline alerts the team; otherwise it proceeds to the next stage, eventually deploying to an environment equivalent to production, ensuring the build is deployable and verifiable.

Amazon Web Services (AWS) provides reliable CI/CD demonstrations, offering extensive resources to configure and monitor pipelines.

Many believe CD’s appeal lies in automating every step from code commit to testing and product release, but manual decisions about what to release remain; continuous deployment removes this final manual step.

Continuous Deployment (CD)

Continuous Deployment extends CD so that once a build passes all tests, it is automatically deployed without human intervention, enabling rapid distribution of components, features, or patches and clearly indicating what is being delivered.

Organizations using continuous deployment can deliver new features quickly, receive fast user feedback, and address defects promptly, helping teams prioritize work that yields real value.

As DevOps evolves, new automation tools for CI/CD pipelines emerge, integrating with code repositories like GitHub and issue trackers like Jira, and running in cloud environments such as GCP and AWS.

The most popular automation tool is Jenkins (formerly Hudson), an open‑source project supported by hundreds of contributors and CloudBees. Other modern commercial products include CircleCI, Codeship, and Shippable, each with its own strengths and trade‑offs.

In our own experience at mabl, we built on Google Cloud Platform and evaluated CircleCI, Codeship, and Shippable. Below are simple tables showing details of each tool.

We ultimately chose Codeship and consider it the right decision, thanks to the support from the Codeship team.

What’s Next?

After modernizing CI/CD pipelines, you may realize that testing also needs modernization. If deployments occur multiple times per day, each test run could take hours; mabl is using machine learning to address this challenge.

Benefits of Continuous Integration

1. Risk Mitigation – Frequent integration reduces the number and severity of merge conflicts, keeping the system’s current state visible.

2. Quality Assurance – Automated builds immediately capture defects, allowing teams to quantify bugs accurately and improve service quality.

3. Visibility & Collaboration – Full visibility into the system enables teams to address small issues before they become large problems.

Challenges of Continuous Integration

1. Organizational Culture Change – Shifting from traditional methods requires retraining and may face resistance from management focused on short‑term goals.

2. Maintenance Overhead – Building and maintaining robust test suites takes time and can slow development if tests are unstable.

3. Noise from Errors – Large teams may see frequent CI error messages, leading to desensitization and accumulation of unnoticed defects.

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