Aurelia unit testing access component's viewModel

Question

I am unit testing one of my components in an Aurelia project. I'd like to access my component's viewModel in my unit test but haven't had any luck so far.

I followed the example available at https://aurelia.io/docs/testing/components#manually-handling-lifecycle but I keep getting component.viewModel is undefined.

Here is the unit test:

describe.only('some basic tests', function() {
    let component, user;

    before(() => {
        user = new User({ id: 100, first_name: "Bob", last_name: "Schmoe", email: 'joe@schmoe.com'});
        user.save();
    });

    beforeEach( () => {
        component = StageComponent
            .withResources('modules/users/user')
            .inView('<user></user>')
            .boundTo( user );
    });

    it('check for ', () => {
        return component.create(bootstrap)
            .then(() => {
                expect(2).to.equal(2);
                return component.viewModel.activate({user: user});
            });

    });

    it('can manually handle lifecycle', () => {

        return component.manuallyHandleLifecycle().create(bootstrap)
            .then(() => component.bind({user: user}))
            .then(() => component.attached())
            .then(() => component.unbind() )
            .then(() => {
                expect(component.viewModel.name).toBe(null);
                return Promise.resolve(true);
        });
    });

    afterEach( () => {
        component.dispose();
    });
});

Here is the error I get:

1) my aurelia tests
       can manually handle lifecycle:
     TypeError: Cannot read property 'name' of undefined

Here is the the line that defines the viewModel on the component object but only if aurelia.root.controllers.length is set. I am not sure how to set controllers in my aurelia code or if I need to do so at all.

I guess my question is: How do I get access to a component's viewModel in my unit tests?

Answer 1

Edit #2:

I'd also like to point out that your own answer is essentially the same solution as the one I first proposed in the comments. It is the equivalent of directly instantiating your view model and not verifying whether the component is actually working.

Edit:

I tried this locally with a karma+webpack+mocha setup (as webpack is the popular choice nowadays) and there were a few caveats with getting this to work well. I'm not sure what the rest of your setup is, so I cannot tell you precisely where the error was (I could probably point this out if you told me more about your setup).

In any case, here's a working setup with karma+webpack+mocha that properly verifies the binding and rendering:

https://github.com/fkleuver/aurelia-karma-webpack-testing

The test code:

import './setup';
import { Greeter } from './../src/greeter';
import { bootstrap } from 'aurelia-bootstrapper';
import { StageComponent, ComponentTester } from 'aurelia-testing';
import { PLATFORM } from 'aurelia-framework';
import { assert } from 'chai';

describe('Greeter', () => {
  let el: HTMLElement;
  let tester: ComponentTester;
  let sut: Greeter;

  beforeEach(async () => {
    tester = StageComponent
      .withResources(PLATFORM.moduleName('greeter'))
      .inView(`<greeter name.bind="name"></greeter>`)
      .manuallyHandleLifecycle();

    await tester.create(bootstrap);
    el = <HTMLElement>tester.element;
    sut = tester.viewModel;
  });

  it('binds correctly', async () => {
    await tester.bind({ name: 'Bob' });

    assert.equal(sut.name, 'Bob');
  });

  it('renders correctly', async () => {
    await tester.bind({ name: 'Bob' });
    await tester.attached();

    assert.equal(el.innerText.trim(), 'Hello, Bob!');
  });
});

greeter.html

<template>
  Hello, ${name}!
</template>

greeter.ts

import { bindable } from 'aurelia-framework';

export class Greeter {
  @bindable()
  public name: string;
}

setup.ts

import 'aurelia-polyfills';
import 'aurelia-loader-webpack';
import { initialize } from 'aurelia-pal-browser';

initialize();

karma.conf.js

const { AureliaPlugin } = require('aurelia-webpack-plugin');
const { resolve } = require('path');

module.exports = function configure(config) {
  const options = {
    frameworks: ['source-map-support', 'mocha'],
    files: ['test/**/*.ts'],
    preprocessors: { ['test/**/*.ts']: ['webpack', 'sourcemap'] },
    webpack: {
      mode: 'development',
      entry: { setup: './test/setup.ts' },
      resolve: {
        extensions: ['.ts', '.js'],
        modules: [
          resolve(__dirname, 'src'),
          resolve(__dirname, 'node_modules')
        ]
      },
      devtool: 'inline-source-map',
      module: {
        rules: [{
          test: /\.html$/i,
          loader: 'html-loader'
        }, {
          test: /\.ts$/i,
          loader: 'ts-loader',
          exclude: /node_modules/
        }]
      },
      plugins: [new AureliaPlugin()]
    },
    singleRun: false,
    colors: true,
    logLevel: config.browsers && config.browsers[0] === 'ChromeDebugging' ? config.LOG_DEBUG : config.LOG_INFO, // for troubleshooting mode
    mime: { 'text/x-typescript': ['ts'] },
    webpackMiddleware: { stats: 'errors-only' },
    reporters: ['mocha'],
    browsers: config.browsers || ['ChromeHeadless'],
    customLaunchers: {
      ChromeDebugging: {
        base: 'Chrome',
        flags: [ '--remote-debugging-port=9333' ]
      }
    }
  };

  config.set(options);
};

tsconfig.json

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "importHelpers": true,
    "lib": ["es2018", "dom"],
    "module": "esnext",
    "moduleResolution": "node",
    "sourceMap": true,
    "target": "es2018"
  },
  "include": ["src"]
}

package.json

{
  "scripts": {
    "test": "karma start --browsers=ChromeHeadless"
  },
  "dependencies": {
    "aurelia-bootstrapper": "^2.3.0",
    "aurelia-loader-webpack": "^2.2.1"
  },
  "devDependencies": {
    "@types/chai": "^4.1.6",
    "@types/mocha": "^5.2.5",
    "@types/node": "^10.12.0",
    "aurelia-testing": "^1.0.0",
    "aurelia-webpack-plugin": "^3.0.0",
    "chai": "^4.2.0",
    "html-loader": "^0.5.5",
    "karma": "^3.1.1",
    "karma-chrome-launcher": "^2.2.0",
    "karma-mocha": "^1.3.0",
    "karma-mocha-reporter": "^2.2.5",
    "karma-source-map-support": "^1.3.0",
    "karma-sourcemap-loader": "^0.3.7",
    "karma-webpack": "^3.0.5",
    "mocha": "^5.2.0",
    "path": "^0.12.7",
    "ts-loader": "^5.2.2",
    "typescript": "^3.1.3",
    "webpack": "^4.23.1",
    "webpack-dev-server": "^3.1.10"
  }
}

Original answer

If you're manually doing the lifecycle, you need to pass in a ViewModel yourself that it can bind to :)

I don't remember exactly what's strictly speaking needed so I'm quite sure there's some redundancy (e.g. one of the two bindingContexts passed in shouldn't be necessary). But this is the general idea:

const view = "<div>${msg}</div>";
const bindingContext = { msg: "foo" };
StageComponent
  .withResources(resources/*optional*/)
  .inView(view)
  .boundTo(bindingContext)
  .manuallyHandleLifecycle()
  .create(bootstrap)
  .then(component => {
    component.bind(bindingContext);
  }
  .then(component => {
    component.attached();
  }
  .then(component => {
    expect(component.host.textContent).toEqual("foo");
  }
  .then(component => {
    bindingContext.msg = "bar";
  }
  .then(component => {
    expect(component.host.textContent).toEqual("bar");
  };

Needless to say, since you create the view model yourself (the variable bindingContext in this example), you can simply access the variable you declared.

Answer 2

In order to get it to work, I had to use Container:

import { UserCard } from '../../src/modules/users/user-card';
import { Container } from 'aurelia-dependency-injection';


describe.only('some basic tests', function() {
    let component, user;

    before(() => {
        user = new User({ id: 100, first_name: "Bob", last_name: "Schmoe", email: 'joe@schmoe.com'});
        user.save();
    });

    beforeEach(() => {
        container = new Container();
        userCard = container.get( UserCard );
        component = StageComponent
            .withResources('modules/users/user-card')
            .inView('<user-card></user-card>')
            .boundTo( user );
    });

    it('check for ', () => {
        return component.create(bootstrap)
            .then(() => {
                expect(2).to.equal(2);
                return userCard.activate({user: user});
            });
    });
});