Every application needs quality testing strategies to function properly and ensure resiliency and reliability for its infrastructure. Microservices are typically small independent services, as a result, they need to be tested independently and specifically for the feature they implement.

To ensure that microservices written in Go are reliable and functional, a thorough testing strategy must be developed, including unit, integration, and end-to-end testing. It's also important to consider different aspects of microservices architecture.

By implementing testing strategies and best practices, we can improve the testing process and ensure that the microservices are working as well as they can. Let's discuss some testing strategies and best practices for microservices written in Go.

Unit testing

Testing a single unit or small piece of code is called Unit Test. As we know, microservices are small independent, and isolated services that are supposed to do one single operation, engineers must write test cases for those services. Ideally, a Unit test is quite voluminous and is internal to the microservice. It should be an automated process and depends on the development framework within the service.

Unlike monolith where a whole application is combined in a single unit, Microservices take one service as a feature or application and it is easier to test them in unit testing. Since there will be a separate microservice single business function, developers and quality engineers can achieve the utmost accuracy in software along with massive cost reduction compared to reworking and buggy applications.

Unit testing in Go

To ensure that your Go microservices are functioning correctly, start by creating unit tests for each function and method. The Go testing framework can be used to generate test cases and assertions. If a function interacts with external services or has dependencies, it's recommended to use mocking libraries or create mock objects to isolate the unit being tested. It's important to cover edge cases, error handling, and boundary conditions in the unit tests to ensure your microservices are robust.

Below are some popular libraries for testing and mocking in Go:

• gomock - Mocking framework for the Go programming language.

• assert - Basic Assertion Library used alongside native go testing, with building blocks for custom assertions.

• gomega - Rspec like matcher/assertion library.

• Testify - Toolkit for mocks, and assertions.

• ginkgo - BDD (Behavior Driven Development) Testing Framework for Go.

Below is a simple example of unit testing in Go via the native testing package:

package main

import (
    "testing"
)

type example struct {
    flag    bool
    counter int
    pi      float64
}

func TestExampleStructCreation(t *testing.T) {
    s1 := example{
        flag:    true,
        counter: 10,
        pi:      3.141592,
    }

    if s1.flag != true {
        t.Error("Expected flag to be true")
    }

    if s1.counter != 10 {
        t.Errorf("Expected counter to be 10, but got %d", s1.counter)
    }

    if s1.pi != 3.141592 {
        t.Errorf("Expected pi to be 3.141592, but got %f", s1.pi)
    }
}

Integration testing

As a software developer, it's important to test your microservices to ensure that they function properly within your workflow. While unit testing is a helpful way to check the individual functionality of each microservice, it's not enough to guarantee that all services will work together seamlessly. Therefore, it's crucial to test the connected services to ensure a smooth working flow. Integration tests validate that independently developed services work smoothly when connected.

Integration testing in Go

Write integration tests to ensure proper communication and interaction between microservices through their APIs or service interfaces. Use test databases for microservices that interact with databases to avoid affecting production data during integration tests.

Below are some popular libraries for integration testing in Go:

• gnomock - integration testing with real dependencies (database, cache, even Kubernetes or AWS) running in Docker, without mocks.

• go-hit - Hit is an HTTP integration test framework written in Golang.

• go-mysql-test-container - Golang MySQL test-container to help with MySQL integration testing.

End-to-end testing

End-to-end or E2E testing is one the most important strategies to test your microservices workflow from start to end to verify the user's journey. These tests can be automated and only done for ultra-critical flows. Unlike, unit or integration testing, it is quite hard to do testing E2E frequently because it requires all microservices to spin up which could be difficult to maintain and automate. As a result, it’s reserved for testing only critical interactions between specific microservices.

When it comes to microservices, problems can arise at various levels, making it a complex system. Even if each service has been thoroughly unit tested, if they cannot communicate with each other, it will not meet the user's expectations. To ensure realistic testing, it's important to create dedicated test environments that closely resemble the production environment. Additionally, implementing end-to-end tests that can be automated and added to your CI/CD pipeline will allow for continuous validation. The more you automate these test flows, the better it will be to manage and fix errors without shipping them into production.

End-to-end testing in Go

For thorough testing of the Go microservices stack, it is crucial to carry out end-to-end tests that cover all the interactions between the microservices. It is highly recommended to establish dedicated test environments that closely resemble the production environment to ensure accurate testing. These end-to-end tests should be automated and integrated into the CI/CD pipeline to facilitate continuous validation. By following these best practices, you can ensure the reliability and efficiency of your microservices stack.

Below are some popular libraries for integration testing in Go:

• httpexpect - Concise, declarative, and easy-to-use end-to-end HTTP and REST API testing.

• baloo - Expressive and versatile end-to-end HTTP API testing made easy.

• endly - Declarative end-to-end functional testing.

Performance testing

Performance testing is a non-functional testing strategy to measure the speed, responsiveness, and stability of a system under a particular workload. In general, it focuses on infrastructure resources such as CPU, GPU, Memory, Network, etc. Performance testing is crucial when running an overwhelming amount of load on your services to find bottlenecks or inability. Most of the performance tests can be achieved by load/stress testing along with benchmarking.

Load or Stress Testing is a type of performance testing used to determine the system's behavior under normal and peak conditions. The goal is to make sure that the application works smoothly under heavy loads when many users access it at the same time. When it comes to testing services, focusing on a single one can be akin to testing the entire stack. While this can be a challenging endeavor that requires careful automation, it is ultimately worth the effort, particularly when dealing with resource-intensive or problematic services.

Performance testing in Go

In Go microservices, it is crucial to perform load testing to evaluate how well your microservices handle concurrent requests and high-traffic loads. In many program languages, a Benchmark is a commonly used tool for measuring the execution time of code. Use Go's built-in benchmarking tool provided by the testing package to measure the performance of critical parts of your code and identify bottlenecks. In the xx_test.go file, we just need to add the function name starting with Benchmark like func BenchmarkXX(). When running the command go test -bench=. , it will trigger the benchmark function.

Below are some popular tools for performance testing in Go:

• mockingjay - Fake server, Consumer Driven Contracts, and help with testing performance.

• Apache JMeter - Test performance both on static and dynamic resources, Web dynamic applications.

• K6.io - A modern load-testing tool, using Go and JavaScript.

Security testing

Security is a crucial aspect of your infrastructure but most of the time engineers do not give real attention to it. The first step is to find the scope and boundaries when considering security testing within microservices. Microservice architecture has a lot of benefits such as scalability, resiliency, and flexibility but it also poses some challenges when it comes to security as each microservice may have its vulnerabilities, dependencies, and communication protocols. Developers and security engineers need to assess the risks and threats that microservices might contain. This requires security to be considered on every layer of your microservice application starting with infrastructure.

Threat Modeling is a process that defines the flow of the system or microservices and helps to identify all the points of attack that hackers could exploit. Engineers need to use tools like OWASP Threat Dragon, Microsoft Threat Modeling Tool, or NIST Cybersecurity Framework to conduct a systematic and structured risk assessment. OWASP's Top 10 security principles are a great way to assess vulnerabilities and risks within your microservices.

Security testing in Go

When working with microservices developed in Golang, it is no exception that we need to use security tools. We should use static analysis tools like GoSec to scan your codebase for security vulnerabilities. This tool inspects source code for security problems by scanning the Go AST. Security engineers also need to conduct penetration testing to identify vulnerabilities in your microservices, APIs, and endpoints. There are tools already available like Burp Suite, OWASP ZAP, or Nmap, to perform penetration testing, fuzzing, and injection attacks on the web application and its microservices

Below are some popular tools for security and testing in Go:

• gosec - Security Checker that inspects source code for security problems by scanning the Go AST.

• secret - Prevent your secrets from leaking into logs, std*, etc.

• secureio - An keyexchanging+authenticating+encrypting wrapper and multiplexer for io.ReadWriteCloser based on XChaCha20-poly1305, ECDH and ED25519.

• Coraza - Enterprise-ready, mod security, and OWASP CRS compatible WAF library

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