@imposter-js/imposter
v1.0.1
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Run integrated tests with Imposter.
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Imposter Mock Engine
Bindings for using the Imposter mock engine in JavaScript/Node.js.
Embed live HTTP mocks within your tests, based on OpenAPI specification files or plain REST APIs.
Usage
const {mocks} = require('@imposter-js/imposter');
// start a mock from an OpenAPI spec file on a specific port
await mocks.builder()
.withPort(8080)
.withOpenApiSpec('/path/to/openapi_spec.yaml')
.start();
// call one of the endpoints defined in the OpenAPI spec
const response = await axios.get('http://localhost:8080/products');
// print JSON returned from the mock
console.log(response.data);
This is just a simple example. Your mocks can have dynamic responses, request validation against an OpenAPI schema, data capture, performance delays etc...
See the sample directory for a Node.js project with many examples.
Quickstart
Imposter is available as an npm package.
Install with npm:
npm install --save-dev @imposter-js/imposter
Or add to your package.json
as a dev dependency:
"devDependencies": {
"@imposter-js/imposter": "*"
}
See available versions on the npm registry
Prerequisites
- Install Imposter CLI. Supports macOS, Linux, Windows.
- Ensure you satisfy the CLI requirements (either Docker installed and running, or a JVM installed).
Examples
See the sample directory for a Node.js project with many examples.
Example with Jest
Here's an example using Jest:
const {mocks} = require('@imposter-js/imposter');
jest.setTimeout(30000);
beforeAll(async () => {
// path to Imposter config directory
const configDir = `/path/to/order-api`;
// start a mock on a specific port
await mocks.start(configDir, 8080);
});
afterAll(async () => {
mocks.stopAll();
});
it('places an order', async () => {
// configure the unit under test
const orderService = new OrderService('http://localhost:8080/orders');
// call your unit under test, which invokes the mock
const confirmation = await orderService.placeOrder('product-05');
// assert values returned by the mock
expect(confirmation.total).toEqual(18.00);
});
Example using just an OpenAPI file
Here's an example mock that just uses an OpenAPI file:
// start a mock from a bare OpenAPI spec file
// requests are validated against the spec
const mock = await mocks.builder()
.withOpenApiSpec('/path/to/pet-names-api.yaml')
.withRequestValidation()
.start();
// call the mock
const response = await axios.get(`${mock.baseUrl()}/names`);
// Output: [ 'Fluffy', 'Paws' ]
// This is driven by either the 'examples' property
// in the OpenAPI spec, or the schema of the response.
console.log(response.data);
Example with no config file
Here's an example mock that doesn't require any configuration file:
const builder = mocks.builder().withPlugin('rest');
// add a POST resource with a path parameter
const resource = builder.addResource('/users/{userName}', 'POST');
// capture the userName path parameter from the request
// for later use in the response
resource.captures().fromPath('userName');
// respond with a templated message indicating the user
// was created by name
resource.responds(201)
.withTemplateData('${request.userName} registered')
.withHeader('Content-Type', 'text/plain');
// spin it up
const mock = await builder.start();
// call the mock
const response = await axios.post(`${mock.baseUrl()}/users/alice`);
// Output: alice registered
// This will vary dynamically, based on the request.
console.log(response.data);
Documentation
- Imposter user documentation - this is the main documentation
- Mock engine configuration - configuration for different engine types
Features
- run standalone mocks in place of real systems
- turn an OpenAPI/Swagger file into a mock API for testing or QA (even before the real API is built)
- decouple your integration tests from the cloud/various back-end systems and take control of your dependencies
- validate your API requests against an OpenAPI specification
Send dynamic responses:
- Provide mock responses using static files or customise behaviour based on characteristics of the request.
- Power users can control mock responses with JavaScript.
Acknowledgements
This project is only possible thanks to the following: