The Changing Landscape of QA

A circuit breaker is a safety device designed to protect an electrical circuit from damage caused by overloads or short circuits. It automatically interrupts the flow of electricity when it detects a fault, preventing potential hazards like fires or equipment damage. Once the issue is resolved, the breaker can be reset to restore power.

In quality assurance (QA), the concept of a circuit breaker can be applied as a design pattern in software testing and system reliability. It works by monitoring the performance of an application or service and temporarily halting operations when failures exceed a certain threshold. This prevents the system from continuing to execute faulty processes and allows time for troubleshooting.

Thanks,

Ramanan 

A circuit breaker is a design pattern used in software development to prevent a system from continuously performing an operation that is likely to fail, helping maintain stability and improve fault tolerance. It works similarly to an electrical circuit breaker: when a failure threshold is exceeded, it "trips" and prevents further execution of the failing process until the system recovers.

1. Preventing System Overload: By stopping repeated calls to failing components, circuit breakers prevent cascading failures and excessive resource consumption.

2. Enhancing Testing Strategies: In QA environments, circuit breakers can be used to simulate real-world failure conditions, helping teams understand system behavior under stress.

3. Improving Reliability Metrics: QA teams can measure failure rates and response times to assess system robustness.

4. Fault Injection & Recovery Testing: Circuit breakers can help test system resilience by deliberately triggering failures and observing how the application recovers.

5. Monitoring & Alerting: Integrated logging and monitoring help detect recurring issues, aiding in proactive quality assurance.

A circuit breaker prevents repeated failures by stopping calls to failing services after a threshold. In Quality Assurance, it helps test fault tolerance, performance, and resilience by simulating failures, validating fallback mechanisms, and ensuring recovery. Tools like Resilience4j, Hystrix, and Polly aid in testing circuit breakers effectively.

Using circuit breakers in QA improves test coverage by simulating real-world failures, ensuring system resilience, and preventing cascading failures. By integrating them into automation and performance testing, QA teams can validate fault tolerance, recovery strategies, and system robustness efficiently.

A circuit breaker is a mechanism that monitors the interactions between services and stops the flow of requests when a failure is detected. It works similarly to an electrical circuit breaker, which interrupts the flow of electricity to prevent damage. In software, it helps to:

1. Prevent cascading failures: By stopping requests to a failing service, it prevents the failure from spreading to other parts of the system.
2. Improve fault tolerance: It allows the system to recover gracefully from failures.
3. Enhance resilience: By providing fallback mechanisms and retry logic, it ensures the system remains operational even when some components fail.

Implementing Circuit Breakers

Circuit breakers can be implemented using various libraries and frameworks depending on the technology stack. Here are a few examples:

• Java: Hystrix, Resilience4j
• .NET: Polly
• JavaScript/Node.js: Opossum
• Python: PyCircuitBreaker

Example: 

// Code Generated by Sidekick is for learning and experimentation purposes only.
import io.github.resilience4j.circuitbreaker.CircuitBreaker;
import io.github.resilience4j.circuitbreaker.CircuitBreakerConfig;
import io.github.resilience4j.circuitbreaker.CircuitBreakerRegistry;

import java.time.Duration;

public class CircuitBreakerExample {
    public static void main(String[] args) {
        CircuitBreakerConfig config = CircuitBreakerConfig.custom()
                .failureRateThreshold(50)
                .waitDurationInOpenState(Duration.ofMillis(1000))
                .slidingWindowSize(2)
                .build();

        CircuitBreakerRegistry registry = CircuitBreakerRegistry.of(config);
        CircuitBreaker circuitBreaker = registry.circuitBreaker("example");

        // Simulate a call
        try {
            circuitBreaker.executeSupplier(() -> {
                // Call to external service
                return "Success";
            });
        } catch (Exception e) {
            System.out.println("Service call failed: " + e.getMessage());
        }
    }
}
 

"Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful."

In Quality Assurance (QA), a Circuit Breaker is a mechanism used to prevent faulty software from continuing to execute when predefined failure thresholds are met. 
It works similarly to an electrical circuit breaker: if a system or process is failing too frequently, the circuit breaker "trips," 
stopping further execution to prevent additional issues.

Key Concepts of Circuit Breaker in QA:
Failure Detection – Monitors system performance and error rates.
Threshold Setting – Defines limits (e.g., number of test failures, API failures, or response time delays).
Automatic or Manual Stop – Halts further execution when the failure threshold is exceeded.
Recovery Mechanism – Allows for testing to resume once the issue is resolved or a cooldown period has passed.

It can be applied as below:
Set a rule, for example:

• If more than 30% of test cases fail, stop further execution.
• If 3 consecutive test runs fail, stop the pipeline.

Real-World Benefits: 
✅Saves time – No need to run all tests if a major issue is detected early.
✅ Prevents false positives – Stops testing when the application is unstable.
✅ Speeds up debugging – Engineers can focus on fixing issues instead of waiting for unnecessary test executions.
✅ Protects test environment – Avoids overwhelming servers with failing requests.

It’s like a safety switch for software. If a service (e.g., payment system, database) starts failing, the circuit breaker stops sending requests to it temporarily. This helps avoid bigger system crashes.  

How it helps with Quality Assurance (QA):
1. Stops Problems Spreading
   - If one part breaks, the circuit breaker “trips” to block requests, keeping the rest working.  
   Example: If a login service fails, users see a “try later” message instead of a broken app.  

2. Saves Time and Resources
   - Skips testing parts that keep failing (e.g., a buggy API), so QA teams focus on stable areas.  

3. Auto-Fixes Bad Releases
   - If a new update causes errors, the circuit breaker can revert to the older, working version automatically.  

4. Finds Weak Spots
   - Test how your app handles failures by simulating crashes. The circuit breaker shows if backups kick in.  

Why it matters for QA:
- Keeps apps running even when parts fail.  
- Makes testing smarter and faster.  
- Helps teams fix issues before users notice.  

Think of it like a fuse in a house: it stops a small problem from burning everything down!

A circuit breaker is a mechanism that monitors the interactions between services and stops the flow of requests when a failure is detected. It works similarly to an electrical circuit breaker, which interrupts the flow of electricity to prevent damage. In software, it helps to:

• Prevent cascading failures: By stopping requests to a failing service, it prevents the failure from spreading to other parts of the system.
• Improve fault tolerance: It allows the system to recover gracefully from failures.
• Enhance resilience: By providing fallback mechanisms and retry logic, it ensures the system remains operational even when some components fail.

 How It Works:

• Closed State: The system works normally, and all requests go through.
• Open State: If failures reach a predefined threshold, the circuit "opens" and stops further requests to the failing service.
• Half-Open State: After a timeout, a few test requests are allowed to check if the system has recovered. If successful, the circuit closes again; if failures persist, it remains open.

Question-What is a circuit breaker and how can we utilise it for quality assurance?

​@JapneetSachdeva 

A circuit breaker is a design pattern in software development that enhances system resilience and fault tolerance, particularly in distributed systems. It acts as an intermediary between dependent services, monitoring their health and responsiveness.

Using circuit breakers in QA improves test coverage by simulating real-world failures, ensuring system resilience, and preventing cascading failures. By integrating them into automation and performance testing, QA teams can validate fault tolerance, recovery strategies, and system robustness efficiently.

Circuit breaker pattern is crucial in modern software engineering, particularly for distributed systems and microservices and its help in 

1.Enhanced system stability

2.Monitoring and observability

3.Fault tolerance in distributed system

P.S -By integrating circuit breakers into system design, developers can build resilient applications that gracefully handle failures and maintain operational stability.

Circuit breaker plays a key role when a system handles failures. For example, when there is a service failure, such as the payment gateway stopping, the system may crash, hang, or become very slow as it keeps trying to reach the failed service. But with a circuit breaker, the system will stop trying to reach the failed service, which will avoid crashing. This will prevent the system from making the problem worse.

A circuit breaker is a design pattern that prevents repeated calls to a failed service, enabling systems to fail gracefully.

How QA Can Leverage Circuit Breakers:
Prevent Flaky Tests – Avoids false failures due to temporary API/service issues.
Enhance Performance Testing – Simulates failures to ensure system resilience.
Improve CI/CD Stability – Prevents pipeline cascading failures.
Detect Defects – Identifies unstable components.
Automate Recovery Testing – Allows easy recovery from failures.

​​​​​​ By incorporating circuit breakers into test automation, QA teams increase resilience and reliability.

The use of a software “circuit breaker”  Firmware example (Bios, IoT, airborne equipment...)

• Firmware update: Booting on old FW, updating FW new. Cannot boot on new, fallback on old FW (but for whatever reason became corrupted), then try to boot again on new FW (that will fail): After x attempts, either boot to “stock” (non alterable) FW or go back to download.
• Cloud based, typically load balancers: Switch to secondary load balancer (fail) then try to switch back to primary load balancer (fail): After x attempts, send an alert message to other components/operators to declare the system unhealthy.

In terms of QA, the mechanism will respond to the following (derived) requirements:

• A Monitoring System shall be in place to alert operators
  • The Monitoring System shall alert in real time operators
  • The Monitoring System shall detect faults at  the systems/processes level
  • The Monitoring System shall detect failures at  the systems/processes level
  • The Monitoring System shall have an interface with the Orchestrator
• An orchestration system shall be in place to assess system readiness
  • The orchestration system shall have an interface with the Monitoring System
  • The orchestration system shall <insert here the what “circuit breaker” shall do>

The requirements covered by such a mechanism (examples)

• SLA (reliability and availability)
• Safety and Compliance
• Robustness
• Performance goals
• ...