API Simulation

API Simulation is a feature that allows you to simulate the behavior of an API. This is useful for testing, demonstration, and development. It decouples the interface implementation from the interface users.

Quick API Simulation

API Simulation is a feature of the ApiGear platform. It allows to simulate the behavior of an API. The apigear command line tool can be used to simulate an API. The following example shows how to simulate the demo API.

API simulation is based on a simulation scenario. The following example shows how to create a simulation scenario for the demo API.

# demo.scenario.yaml
interfaces:
  - name: demo.Counter
    props:
      count: 0
    operations:
      - name: increment
        actions:
          - $set: { count: 1 }
      - name: decrement
        actions:
          - $set: { count: 0 }

Now we can run the simulation server using the following command.

apigear simulate run demo.scenario.yaml

The simulation server will listen on port 5555. To change the port use the --port option. It will load the simulation scenario from the demo.scenario.yaml file. The simulation server will listen for API calls. Normally the API calls will come from a running API client. It is also possible to feed API calls using the feed command.

The following example shows how to feed API calls to the simulation server using a new line delimited json document (NDJSON).

{ "method": "simu.state", "params": { "symbol": "demo.Counter" }}
{ "method": "simu.call", "params": { "symbol": "demo.Counter/increment", "data": { "step": 1 } }}
{ "method": "simu.call", "params": { "symbol": "demo.Counter/decrement", "data": { "step": 2 } }}
{ "method": "simu.state", "params": { "symbol": "demo.Counter", "data": { "count": 4 } }}
{ "method": "simu.state", "params": { "symbol": "demo.Counter" }}

To feed the API calls to the simulation server just run the following command.

apigear simulate feed demo.ndjson

This will send the API calls to the simulation server. The simulation server will print the API calls to the console.