# Never Test in Production 🚫🔧

## Definition of Production 📦

* **Production Environment**: The live environment where services are actively delivered to users. For example, a website's live server or an authentication service handling user logins.

## Importance of Testing Changes 🧪

Before implementing any changes, it’s crucial to test them in a non-production environment to avoid disrupting live services.

### **Test Environment** 🖥️

* **Purpose**: Mimics the production environment but does not serve actual users.
* **Benefit**: Allows you to identify and fix issues without impacting users.

### **Secondary or Stand-By Machine** 💻

* **Purpose**: A duplicate of the production machine that remains inactive until needed.
* **Process**: Apply changes to the stand-by machine first. Once verified, switch it with the primary machine and update the original primary machine.

### **Canary Releases** 🦠

* **Concept**: Similar to coal miners’ canaries used to detect gas, use a small subset of servers to test changes.
* **Purpose**: Minimize risk by exposing only a small user base to new changes before full deployment.
* **Process**: After successful testing on canaries, deploy changes to the entire fleet.

## Testing Minor Changes 🧩

* **Principle**: Even minor changes should be tested in a test environment before applying to production.
* **Reason**: Prevent unforeseen issues and ensure stability.

## Summary 📋

1. **Always Test First**: Use a test environment to verify changes before applying them to production.
2. **Utilize Secondary Machines**: Apply changes to a stand-by machine first to ensure stability.
3. **Employ Canary Releases**: Test changes on a subset of servers to mitigate risk.
4. **Even Minor Changes**: Test all changes, regardless of size, to maintain service reliability.