Testing Locally

Testing is among the most important tasks in the cycle of software development. EXM provides the necessary SDK functions to facilitate testing in a way that can be readable & efficient.

Why Testing Locally?

No testing your EXM applications locally can lead to:
  • Exceeding the maximum of deployments allowed
  • Slowness in development by needing to wait for eventual consistency to take place
  • Increase of unnecessary account usage

Testing Locally

In order to test applications locally inside EXM's environment, you will need to install EXM's Javascript SDK. For more information, click here.
After having installed the Javascript SDK, we'll take a look at the following examples.
// import { ... } from '@execution-machine/sdk'
const { TestFunction, createWrite, FunctionType } = require("@execution-machine/sdk");
const { readFileSync } = require("fs");
const testAttempt = await TestFunction({
functionSource: readFileSync("users-registry.js"),
functionType: FunctionType.JAVASCRIPT,
functionInitState: {
users: []
writes: [createWrite({ username: "Andres" })]
assert(testAttempt.state.users, [{ username: "Andres" }]);
assert(testAttempt.result, 1);
  • Necessary functions are imported from @execution-machine/sdk and fs
  • TestFunction creates an execution context simulating in real time what EXM does
  • createWrite creates an object that satisfies the internal write operation interface
* @param state is the current state your application holds
* @param action is an object containing { input, caller } . Most of the times you will only use `action.input` which contains the input passed as a write operation
* @returns {Promise<{ users: Array<{ username: string}> }>}
export async function handle(state, action) {
const { username } = action.input;
state.users.push({ username });
return { state, result: state.users.length };
  • The function above receives a property username in an object passed as input
  • the username property is added to state.users (an array)
  • state.users is initialized during deployment with initial state {"users": []}
In the example above, we can see how TestFunction is called.
  • When this function is called, the functionSource buffer is provided through readFileSync which is reading the application's source ode (user-registry.js)
  • functionType is explicitly specified to be a Javascript application
  • functionInitState contains the initial state of our simulated deployment, in this case, an empty array called users
  • writes is an array with the instructions to be executed following the internal write operation interface. createWrite facilitates abstract the use of such interface into a method that receives an input and tags (optionally). The input passed in createWrite is equivalent to action.input in your function.