Presets

Using presets

You can tell a fixture to use a preset to build its response by simply calling its preset method with the name of the preset :

const server = new Server();

server.respond.with.preset(400);

The preset is only evaluated and merged by the fixture at request time. You can easily override preset options through fixture response configuration.

If the preset is not found in the server instance, an exception will be raised at request time.

Local presets

Adding/editing a local preset

It can be done by providing an object with its set method and/or using BDD style syntax. Alternatively, the configuration object can be provided to server.preset :

const server = new Server();

// In the server.preset call
server.preset('myPreset', {
  status: 250
  statusText: 'weird status'
});

// Another syntax, the same result
server.preset('myPreset').set({status: 250}).statusText('weird')

Server will now have myPreset available in its own presets pool. If the presets was already defined, it will be overridden with new options.

Note : the options that are not overridden will be kept as is.

const server = new Server();

server.preset('myPreset', {status: 250, statusText: 'weird status'});

// Later on
server.preset('myPreset').status(200);
// statusText will still equal 'weird status'

You can have a look at the response configuration for more details about the available options.

Removing preset

Simply call the remove method of the preset :

  server.preset('myPreset').remove();

Using global presets

Aside local presets that can be defined within a server instance, FMF allows the registration of global presets. Global presets can be added/updated/removed in two ways :

Global presets singleton exports

Global presets are stored in a singleton available through the presets export. Object can be updated at will.

import {presets} from 'fetch-mock-fixtures';

presets.myPreset = {
  status: 250
  statusText: 'weird status'
} // myPreset will now be available globally

That way is interesting when bootstrapping presets configuration before running tests suite.

Register/unregister a local preset as global

Since FMF 2.2.0, it is possible to manage global presets from any server instance.

Any local preset can be made global through register method and any global preset can be removed with unregister method.

const server = new Server();
// Create a local preset
const myPreset = server.preset('myPreset', {status: 250, statusText: 'weird status'});
// And register it as global
myPreset.register();
// Remove the preset from global pool
// It will still be available in the server instance
myPreset.unregister();

Methods are chainable :

const server = new Server();

// Register the preset, unregister it and remove it from server presets pool
server.preset('myPreset').status(250).register().unregister().remove();

Global presets availability

To allow easy local tweaking of presets, global presets are cloned into local pool when creating a new server instance. Therefore, server's instance will only access global presets that are already defined before its creation or created within the server instance.

Built-in presets

FMF already have commonly used built-in presets. See presets.js for details.