gRPC is getting increasingly popular with each passing year. According to Postman’s 2022 State of the API Report, gRPC is the fifth most popular API architecture, accounting for 11% of APIs.

gRPC stands for Google Remote Procedure Call. It’s an open-source protocol that works in any environment. It’s also excellent for distributed applications and services, as it can call resources from other machines as if they were a local object. gRPC is incredibly fast, as well, as it’s up to 25 times faster than REST.

API testing is one of the top priorities for API developers. Continuous testing is imperative to ensure your API operates efficiently, safely, and securely. With that in mind, we’ve put together some tips on optimizing your gRPC testing. Before we delve into the how, though, let’s start with the why.

Benefits of gRPC Testing

gRPC is capable of stunning performance, as we’ve already mentioned. Unfortunately, servers aren’t always able to keep up with gRPC’s capabilities. These limitations mean you might not be able to see what your gRPC API is truly capable of.

The first benefit of gRPC testing is you can use automation to simulate the conditions of heavy loads to see what your gRPC API is truly capable of. Secondly, API testing is an essential component of a CI/CD pipeline, as it often involves a lot of tests that need to be performed regularly.

Automated gRPC testing also eliminates the need for repetitive, mindless testing. Removing the busywork means you and your development team can focus on more imaginative and challenging tests, giving you a more thorough overview of your gRPC API’s performance.

6 Tips for gRPC Testing

Now let’s take a look at some best practices for gRPC testing.

Understand .proto Files

gRPC is similar to other API architectural styles, like REST, but there are some key differences. One main difference is .proto files, which are payloads similar to JSON files in REST. .proto files contain all API contracts, including API requests, responses, and service names.

.proto files can generate, launch, and run both clients and servers once they’re defined. They can also be written in virtually any language. For more info on .proto, advice on how to get started with them, and examples for some of the most popular programming languages, read the gRPC documentation.

Understand Protocol Buffers

Protocol buffers are what make gRPC so fast, lightweight, and efficient. They’re a language-neutral, platform-neutral, and extremely customizable way to send serialized data. Protocol buffers let you define your data structure and then write your own code for quickly reading and writing data following that structure.

Protocol buffers can be written in most popular programming languages, including Java, Python, Objective-C, and C++. With the introduction of proto3, protocol buffers now support Kotlin, Dart, Go, Ruby, and C#, as well.

To get started with protocol buffers, start by downloading and installing the compiler. Next, read the protocol buffer overview. Then find a tutorial for your preferred programing language.

Implement Benchmarking

To truly understand how your gRPC API is performing, you must know what to look for. Benchmarking is an important aspect of gRPC testing, as it allows you to continually monitor and measure different metrics.

gRPC features a native tool for benchmarking, BenchmarkService. BenchmarkService features two separate functions for benchmarking, BenchmarkService.UnaryCall and BenchmarkService.StreamingCall. UnaryCall lets you measure how long it takes to return a specific number of bytes. StreamingCall allows for repeated requests and response messages.

Benchmarking can be used to measure contentionless time using StreamingCall. It can also be used to quantify QPS, which is the message per second rate for two clients and 64 channels, each containing 100 messages. It can also tell you your network’s scalability, specifying how many messages per second the network can handle. Benchmarking can be written in most popular programming languages.

Follow the Protobuf Style Guide

In REST, the API contract is often defined by the server. In gRPC, it’s the other way around — the server is defined and implemented in the protobuf file, which then generates the client and server stubs.

This makes following the style guide by Google highly recommended, as it helps to ensure your file will be able to be read by automated code generators.

Some best practices laid out by Google include:

• Keep line length to 80-characters or less
• Use an indentation of two spaces
• Prioritize double quotes for string inputs
• Use lower_case_protocol for naming files

Also, they recommend that files should adopt the following format:

1. License header (if applicable)
2. File overview
3. Syntax
4. Package
5. Imports (sorted)
6. File options
7. Everything else

Decide On Your Testing Environment

A number of API testing tools and environments now support gRPC testing. Some API management tools that support gRPC testing include Postman, Insomnia, Kreya.app, and BloomRPC. They each have their strengths and drawbacks, but they’re all robust and capable. Picking the right gRPC testing tool will largely be a matter of taste.

We’re big fans of Postman over here, due to its popularity and ease of use. This makes it easy to get up and running with gRPC testing in no time. It’s not possible to import .proto files using Postman, unfortunately, so you’ll need to put together a set of files to import if you go with Postman.

Postman and Insomnia are both general HTTP API management tools. Kreya.app and BloomRPC both deal with gRPC specifically, on the other hand. With that in mind, if you’re doing other API testing, we recommend Postman. If you’re looking for a gRPC testing environment specifically, we recommend Kreya for its built-in test sampler and general convenience.

Learn By Example

gRPC is becoming increasingly prevalent. This means there are plenty of tools and tutorials out there to learn from. Here’s a GitHub repository with a wide range of gRPC testing tools written for Cucumber, for example. Resources like add first line of code give you a template to work from. Even better still, the code is exquisitely annotated, offering invaluable insight into the author’s thought process and getting you in the habit of thinking like a gRPC developer.

Final Thoughts: The Future Of gRPC

REST APIs have dominated the industry for almost as long as APIs have been around. They’re not without their shortcomings or above reproach, however. gRPC has a few aspects that remedy some of these issues, some of which will become increasingly important as time goes on.

First and most obvious is the performance advantages. Smaller, lighter, faster, and more efficient is always going to be preferable in programming. Even more important is security, though. gRPC uses SSL/TLS to authenticate the server and encrypt all data. Considering the importance of API security, and the prevalence of data breaches, gRPC’s adoption is likely to continue to grow and spread.