Imposter: Scriptable, multipurpose mock server

Reliable, scriptable and extensible mock server for REST APIs, OpenAPI (and Swagger) specifications, SOAP/WSDL Web Services, Salesforce and HBase APIs.

This project is the CLI tool for the Imposter mock engine.

Stand up a live mock from an OpenAPI spec in one command:

$ imposter up -s

found 1 OpenAPI spec(s)
starting server on port 8080...
mock server up and running at http://localhost:8080

You now have a live mock of your OpenAPI spec running on localhost.

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Record HTTP exchanges by proxying a real endpoint, then replay them as a mock:

$ imposter proxy https://example.com

starting proxy on port 8080
wrote response file /users.json for request GET /users
wrote config file example.com-config.yaml

Run imposter up to start the mock you just recorded.

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Or scaffold a mock straight from an OpenAPI/WSDL file:

$ imposter scaffold

found 1 OpenAPI spec(s)
generated 1 resources from spec
wrote Imposter config: /Users/mary/example/petstore-config.yaml

Run imposter up to start your mock.

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Features

• Stand up mocks in place of real systems, locally or in CI
• Turn an OpenAPI/Swagger or WSDL file into a working mock — even before the real API exists
• Decouple integration tests from cloud and back-end dependencies
• Validate requests against an OpenAPI specification
• Capture data and serve conditional, templated responses
• Store data for later retrieval or validation
• Proxy and record an existing endpoint to replay it as a mock
• Drive responses with JavaScript, Groovy, or your own plugin

Install

You'll need Docker, or alternatively a JVM (JVM engine) or no extra runtime at all (Golang engine).

Homebrew

brew tap imposter-project/imposter
brew install imposter

Shell script (macOS and Linux)

curl -L https://raw.githubusercontent.com/imposter-project/imposter-cli/main/install/install_imposter.sh | bash -

For other platforms or manual installs, see Installation.

Common commands

Each command has full help via imposter <command> --help.

Command	What it does
imposter up [DIR]	Start a live mock from Imposter config in DIR (defaults to current directory). Add -s to scaffold first.
imposter scaffold [DIR]	Generate Imposter config from any OpenAPI/Swagger or WSDL files in DIR.
imposter proxy URL	Forward traffic to URL and record each exchange to disk as a replayable mock. Add --insecure to skip TLS verification.
imposter down	Stop running mocks for the current engine type. Add -a to stop them all.
imposter list	List running mocks and their health. -qx makes a tidy healthcheck.
imposter bundle [DIR]	Bundle config and engine into a Docker image or Lambda zip.
imposter doctor	Check that you have at least one engine ready to run.
imposter engine pull / engine list	Manage cached engine binaries and images.
imposter plugin install / list / uninstall	Manage engine plugins.
imposter remote ...	Configure and deploy to a remote Imposter target.
imposter workspace ...	Manage workspaces for remote deployments.
imposter version	Print CLI and engine version info.

Healthcheck

imposter list -qx

Exits 0 if at least one mock is running and healthy, non-zero otherwise.

Logging

Default log level is debug. Override with the LOG_LEVEL environment variable:

export LOG_LEVEL=info

Or per invocation:

imposter up --log-level trace

Configuration

See Configuration for the CLI config file, environment variables, and engine-specific settings.

Other deeper guides:

• Docker engine — the default
• JVM engine
• Golang engine
• Run the CLI itself in Docker
• SDK — embed Imposter in your Go app
• Upgrade

About Imposter

Imposter is a mock server for REST APIs, OpenAPI/Swagger, SOAP/WSDL, Salesforce and HBase.

📖 Full user documentation

Contributing

Suggestions and improvements to the CLI or its documentation are welcome. Please raise pull requests targeting the main branch.