Signadot vs Pact
Pact checks the contract. Signadot runs the change with real services.
Pact catches a broken API contract in your unit tests, with nothing deployed. Signadot gives each change an ephemeral environment with real services, where Smart Tests and your own tests check what contracts leave out.
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Signadot vs Pact: six key differences
They answer different questions, so most teams that use one can use both. Pact checks, with nothing deployed, that a provider still gives each consumer what it expects. Signadot gives each change an ephemeral environment with real services, where Smart Tests compare the changed service with the baseline and your own tests check behavior, data and side effects. For the category, see the complete guide to contract testing.
| Feature | Signadot | Pact |
|---|---|---|
| Foundation | Ephemeral environments with real services. Tests and agents run in them. | Contract tests in your unit test suite. No environment needed. |
| Coding agents | Agents on laptops or in the cloud each get an ephemeral environment for Jobs and Plans. | An MCP server and agent skills that write and review Pact tests. |
| What it checks | Smart Tests compare a changed service with the baseline, on real dependencies. | That a provider still meets each consumer's expectations. |
| Databases, queues and more | Real databases and queues in every environment, through resource plugins and message routing. | Message contracts, not side effects. Database writes are left to other tests. |
| Protocols | Smart Tests cover REST with JSON. Jobs run tests for anything else. | HTTP and messages, plus gRPC and GraphQL through plugins. |
| Testing: Jobs and Plans | Jobs run your tests. Plans let agents build test workflows. | Contract tests only, by design. Functional tests run elsewhere. |
When to choose Pact
The fit for checking that services keep their promises to each other.
- You own both sides of an API and want breaks caught in unit tests
- You want can-i-deploy to gate every release
- You need contracts for messages, gRPC or GraphQL
When to add Signadot
The fit for testing what contracts leave out, with real services.
- Behavior, data and side effects across services
- An ephemeral environment for every PR and coding agent, local or in the cloud
- Smart Tests on every environment, plus your own suites as Jobs
- Plans that coding agents build and run
- A free Starter plan to get going
The bottleneck has shifted from writing code to proving it works.
Agents write code faster than teams can check it. Signadot gives every change its own environment with real services and data, so your tests and agents can show it works.
The Signadot platform
Four pillars of the Signadot platform
Signadot spins up an ephemeral environment for every code change, from a developer's laptop to thousands of coding agents, so your tests and agents can check it against your real services, databases and message queues.
Built for Agents
Run thousands of agents in parallel.
Each agent gets its own lightweight ephemeral environment, cheap and fast to spin up, so agents run more validations on their own before human review.
Unified Architecture
Inner and outer loop, one platform.
The same ephemeral environment covers local development and PR validation. One platform. One mental model.
Comprehensive Coverage
Smart Tests, Jobs and Plans, built in.
Jobs run your existing tests. Plans let agents build test workflows. All of it runs in your cluster.
Deep Isolation
Data, queues and cloud resources.
Share a database or branch it per ephemeral environment. Queues stay shared, with messages routed by key. Resource plugins create cloud resources outside Kubernetes.
Testimonials
Hear from our customers
$2M saved annually
On the margin, with the Signadot approach, 99.8% of the isolated environment's infrastructure costs look wasteful. That percentage looks like an exaggeration, but it's really not.
Connor BraaSoftware Engineering Manager 
83% lower change failure rate
We basically stopped creating full preview environments and replaced our custom solution with Signadot. Instead of isolating the full environment, the strategy using routing keys is much lighter, and we are able to provide an isolated environment, even with isolated databases, per PR quite fast.
Marcus TavaresStaff Software Engineer 
No more fighting over staging
Creating a sandbox is extremely fast, it works every time, lets me test what I'm building quickly, and move on. This is awesome.
Tyler MarienSenior Software Developer 
10x integration capacity
Our engineers were spending more time waiting for an environment than shipping. Now they test against our real services in parallel, which made a whole tier of fixed test infrastructure unnecessary. Retiring environments we had carried for years is projected to save us several million dollars annually.
Jony JeyaratnamHead of Engineering Coding agents
Built for agentic development
Most code is now written by coding agents, on laptops and in the cloud. Each one gets its own ephemeral environment to test in, the same kind a developer uses.
- An MCP server and agent skills that work across the coding agents your teams use
- Background agents running in cloud sandboxes get their own ephemeral environment too (see the Modal example)
- Jobs and Plans that run in each agent's environment
Testing
Run the tests too, with Jobs and Plans
Pact runs in your unit tests. Signadot runs the tests that need real services, in an ephemeral environment.
- Jobs run the test suites you already have
- Plans let agents build automated test workflows
- Your platform team picks the Plans every change must pass
Cloud native stack
Works with your service mesh
Signadot routes through the mesh you already run. On Istio it adds no sidecar of its own: it updates your VirtualService rules and Istio does the routing.
- Istio, natively, in sidecar or ambient mode
- Gateway API: routes beside your HTTPRoutes and GRPCRoutes
- Linkerd or no mesh: a lightweight DevMesh sidecar
- OpenTelemetry baggage carries the routing key
Deployment and security
Runs in your cluster
Most of Signadot runs in your cluster.
Need fully self-hosted? Talk to us.
- Only resource metadata leaves your cluster by default
- Never your code, app data or production PII
- SOC 2 Type II
Built for Developers and Agents
Works with your coding agents
Integrate with CI tools you already use
Support all test frameworks
Signadot is making it easier for our developers to build and test microservices using deployments that are incredibly similar to production. This has made both human and AI-written code easier to validate and test.
Naomi KleinLead Infrastructure Engineer at Laurel Frequently asked questions
Is Signadot an alternative to Pact?
No. Signadot works beside Pact rather than replacing it. Pact checks that a provider still gives each consumer what it expects, in your unit tests, with nothing deployed. Signadot gives each change an ephemeral environment with real services, where Smart Tests and your own tests check behavior, data and side effects, which Pact leaves to other tests.
Pact vs Signadot Smart Tests: what's the difference?
Pact is consumer-driven: each consumer's tests record what it expects from a provider, and the provider replays those requests against its own code. Smart Tests are provider-side: they send the same requests to the changed service and to the baseline in a live environment, and flag the differences that matter. Pact knows what each consumer needs. Smart Tests see how the service behaves with its real dependencies.
Can I use Pact and Signadot together?
Yes. Keep Pact in each service's build and gate releases with can-i-deploy. Then give each pull request an ephemeral environment in Signadot, where Smart Tests run when the environment is created and Jobs run your integration and end-to-end tests against real services. Pact catches a broken contract early. Signadot catches what only shows up with real services, data and queues.
Do Smart Tests need contracts or mocks?
No. You write the requests in a short Starlark script, and Signadot sends them to the changed service and to the baseline in your cluster. A model scores each difference between the responses, so you don't write an assertion for every field, and you add checks where you want one. Smart Tests cover REST APIs with JSON. For other protocols, run your own tests as Jobs.
Who owns Pact, and what does it cost?
Pact is free and open source, maintained under the Pact Foundation with SmartBear as its sponsor. SmartBear bought PactFlow, the hosted Pact Broker, in 2022 and is moving it into Swagger Contract Testing. PactFlow has a free Starter plan and paid Team and Enterprise plans.
Does Signadot work with databases and message queues?
Yes, with any database or queue. Resource plugins create a database for each environment, using tools you already use. Queues stay shared, and each message reaches the right environment. The same works for Temporal. The complete guide to ephemeral environments compares the approaches. Pact checks the shape of each message, not what happens when a service handles it.
Can coding agents use Signadot?
Yes. Coding agents such as Claude Code and Cursor connect through Signadot's MCP server and agent skills. Each agent gets its own ephemeral environment, whether it runs on a developer's laptop or as a background agent in the cloud, and runs Jobs and Plans against it before anyone reviews the change.
Is Signadot self-hosted?
Signadot is hybrid. Most of it runs in your cluster, with a small cloud control plane that only sees resource metadata by default. Need fully self-hosted? Talk to us.