Testing

Event handlers are pure functions (or can be treated as such), making them easy to test in isolation, much like Redux reducers. The @inglorious/store/test module provides utility functions to make this even simpler.

`trigger(entity, handler, payload, api?)`

The trigger function executes an event handler on a single entity and returns the new state and any events that were dispatched.

javascript

import { trigger } from "@inglorious/store/test"

// Define your entity handler
function increment(entity, payload, api) {
  entity.value += payload.amount
  if (entity.value > 100) {
    api.notify("overflow", { id: entity.id })
  }
}

// Test it
const { entity, events } = trigger(
  { type: "Counter", id: "counter1", value: 99 },
  increment,
  { amount: 5 },
)

expect(entity.value).toBe(104)
expect(events).toEqual([{ type: "overflow", payload: { id: "counter1" } }])

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`createMockApi(entities)`

If your handler needs to interact with other entities via the api, you can create a mock API. This is useful for testing handlers that read from other parts of the state.

javascript

import { createMockApi, trigger } from "@inglorious/store/test"

// Create a mock API with some initial entities
const api = createMockApi({
  counter1: { type: "Counter", value: 10 },
  counter2: { type: "Counter", value: 20 },
})

// A handler that copies a value from another entity
function copyValue(entity, payload, api) {
  const source = api.getEntity(payload.sourceId)
  entity.value = source.value
}

// Trigger the handler with the custom mock API
const { entity } = trigger(
  { id: "counter2", type: "Counter", value: 20 },
  copyValue,
  { sourceId: "counter1" },
  api,
)

expect(entity.value).toBe(10)

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The mock API provides:

getEntities(): Returns all entities (frozen).
getEntities(typeName): Returns entities by type (frozen array).
getEntity(id): Returns a specific entity by ID (frozen).
select(selector): Runs a selector against the entities.
dispatch(event): Records an event for later assertions.
notify(type, payload): A convenience wrapper around dispatch.
getEvents(): Returns all events that were dispatched.

Testing #

trigger(entity, handler, payload, api?) #

createMockApi(entities) #

Testing

`trigger(entity, handler, payload, api?)`

`createMockApi(entities)`