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Testing · head to head

k6 vs TestNG

k6 logo

k6

Testing

Load testing tool with JavaScript tests on a Go runtime, now owned by Grafana Labs

From
Free
Rated
-
Full reviewWebsite
TestNG logo

TestNG

Testing

Java testing framework created by Cedric Beust, still actively maintained but effectively a single-lead project

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: k6 tests run on a JavaScript engine embedded in Go rather than on Node.js, so npm packages, Node built-ins and existing shared test utilities generally do not work without being bundled to plain JavaScript, and often not even then.; TestNG maintainership is concentrated around creator Cedric Beust rather than a broad team or foundation, which is a real continuity risk compared to JUnit's independent team or Jest's foundation backing.
  • They diverge on capability: k6 covers JavaScript test scripts, TestNG covers Test dependencies.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which k6 and TestNG actually diverge.

Attributes where k6 and TestNG differ
Attributek6TestNG
PlatformsWindows, macOS, Linux, Docker, KubernetesLinux, macOS, Windows

Identical on both: starting price (Free), pricing model (Open source, no licence fee), free tier (Yes), user rating (Not yet rated), category (Testing).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in k6

  • JavaScript test scripts
  • Thresholds and checks
  • Protocol coverage
  • Browser module
  • Executors
  • xk6 extensions
  • Metrics output
  • Kubernetes operator

Only in TestNG

  • Test dependencies
  • XML suite configuration
  • Native parallel execution
  • Data providers
  • Grouping
  • Flexible reporting

What people use each for

The jobs each tool is most often brought in to do.

k6

  • Gating a deployment pipeline on a threshold such as 95th percentile latency under a defined arrival ratenot TestNG
  • Generating tens of thousands of requests per second from a small number of machines without a load generator fleetnot TestNG
  • Testing gRPC and WebSocket services with the same tooling and thresholds used for HTTP endpointsnot TestNG
  • Correlating a load test against existing dashboards for an organisation already running Grafana and Prometheusnot TestNG

TestNG

  • A Java integration test suite that needs to skip dependent tests automatically when a prerequisite test failsnot k6
  • A team wanting XML-based suite configuration to manage large, grouped test suites without touching code for each runnot k6
  • A project needing native parallel test execution at the class or method level without adding a separate pluginnot k6
  • A Selenium-based UI test suite that uses TestNG as the underlying runner for grouping and parallelisationnot k6

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

k6

  • Tests run on a JavaScript engine embedded in Go rather than on Node.js, so npm packages, Node built-ins and existing shared test utilities generally do not work without being bundled to plain JavaScript, and often not even then.
  • The open source binary runs on a single machine, so distributed load requires the Kubernetes operator or the cloud service, and the operator is infrastructure your team has to run and debug.
  • The AGPL-3.0 licence on the core requires legal review at any company that intends to embed k6 in a product it distributes or offers as a service, which is a slower path than a permissively licensed tool.
  • There is no result storage in the open source tool, so trend history means standing up Prometheus, InfluxDB or Grafana Cloud before load testing produces anything comparable over time.
  • Since the Grafana Labs acquisition the roadmap serves the Grafana observability stack, so a buyer choosing k6 as a standalone tool should expect the standalone experience to receive less investment than the cloud and dashboard integration.
  • Grafana Cloud billing is by virtual user hour, so a long soak test at modest concurrency costs far more than its peak load suggests, and cost planning has to be done in virtual user hours rather than in test runs.

TestNG

  • Maintainership is concentrated around creator Cedric Beust rather than a broad team or foundation, which is a real continuity risk compared to JUnit's independent team or Jest's foundation backing.
  • It is a smaller ecosystem than JUnit, so fewer third-party integrations, tutorials and Stack Overflow answers exist for edge cases.
  • XML-based suite configuration, while powerful, is an extra file and syntax to maintain alongside the codebase, which some teams find adds friction JUnit's more code-centric model avoids.
  • There is no commercial support tier or vendor relationship of any kind, unlike JUnit's OpenElements arrangement, so an enterprise wanting a support contract has no route to buy one.
  • Release cadence, while active, is slower and less frequent than JUnit 5's, since it depends on a much smaller pool of active maintainers.

Pricing, plan by plan

k6

Free
  • k6 OSSFree
    • AGPL-3.0 licence
    • Full test engine, no virtual user limits
    • Runs on one machine unless distributed yourself
  • Grafana Cloud free tierFree
    • Includes a monthly allowance of virtual user hours
    • Hosted test results and dashboards
    • Shared with the rest of the Grafana Cloud free tier
  • Grafana Cloud k6$undefined/month
    • Billed by virtual user hours consumed
    • Load generation from multiple regions
    • Retained test history and comparison

TestNG

Free
  • TestNGFree
    • Full functionality, no usage limits
    • Community support via GitHub
    • No commercial support tier exists

Which should you pick?

Choose k6 if

  • You need javascript test scripts.
  • You want to start without paying.
  • You work on Windows, macOS, Linux, Docker, Kubernetes.
  • You also want thresholds and checks.
k6 review

Choose TestNG if

  • You need test dependencies.
  • You want to start without paying.
  • You work on Linux, macOS, Windows.
  • You also want xml suite configuration.
TestNG review

Questions people ask

Is k6 or TestNG better?
Neither clearly leads. k6 starts at Free and TestNG at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, k6 or TestNG?
k6 starts at Free and TestNG at Free.
Does k6 or TestNG run on more platforms?
k6 runs on Windows, macOS, Linux, Docker, Kubernetes. TestNG runs on Linux, macOS, Windows.
Can I use k6 for free?
Both have a free tier, so you can try either at no cost before committing.
What is k6 best used for?
k6 is most often used for gating a deployment pipeline on a threshold such as 95th percentile latency under a defined arrival rate, generating tens of thousands of requests per second from a small number of machines without a load generator fleet, testing grpc and websocket services with the same tooling and thresholds used for http endpoints, correlating a load test against existing dashboards for an organisation already running grafana and prometheus. Of those, gating a deployment pipeline on a threshold such as 95th percentile latency under a defined arrival rate and generating tens of thousands of requests per second from a small number of machines without a load generator fleet are not what TestNG is typically brought in for.
What can k6 do that TestNG cannot?
k6 covers JavaScript test scripts, Thresholds and checks, Protocol coverage, Browser module. TestNG covers Test dependencies, XML suite configuration, Native parallel execution, Data providers.

Answered from the vendors’ own pages

k6: Can I use npm packages in a k6 test?

Usually not. Scripts run on a Go-embedded JavaScript engine with no Node.js runtime, so packages depending on Node built-ins fail and pure JavaScript libraries must be bundled first.

TestNG: Is TestNG still actively maintained in 2026?

Yes, it continues to receive releases in its 7.x line with support for current Java versions, though maintenance is concentrated around a small team led by its creator.

k6: Is k6 free?

The core tool is free under AGPL-3.0 with no virtual user limits. Grafana Cloud k6 is a paid service billed by virtual user hours, with a free monthly allowance.

TestNG: What does TestNG offer that JUnit does not?

Native test dependencies, XML-based suite configuration and built-in parallel execution without needing external plugins, all of which JUnit users typically add via separate libraries.

k6: Does the Grafana acquisition affect the open source tool?

The tool remains open source and maintained, but investment is directed at making it a data source for Grafana, so standalone use is supported rather than prioritised.

TestNG: Is there a commercial support option for TestNG?

No, unlike JUnit there is no commercial support arrangement; support is purely community-based through GitHub.

k6: Can k6 replace a browser testing tool?

No. The browser module measures page-level metrics under load, but functional browser testing belongs in Playwright or a similar tool.

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