In the Vue.js documentation, there is an example of a custom input component. I'm trying to figure out how I can write a unit test for a component like that. Usage of the component would look like this
<currency-input v-model="price"></currency-input>
The full implementation can be found at https://vuejs.org/v2/guide/components.html#Form-Input-Components-using-Custom-Events
The documentation says
So for a component to work with
v-model
, it should (these can be configured in 2.2.0+):
- accept a value prop
- emit an input event with the new value
How do I write a unit test that ensures that I've written this component such that it will work with v-model
? Ideally, I don't want to specifically test for those two conditions, I want to test the behavior that when the value changes within the component, it also changes in the model.
You can do it:
<currency-input>
<currency-input>
with a value that it transforms (13.467
is transformed by <currency-input>
to 13.46
)price
property (bound to v-model
) has changed.Example code (using Mocha):
import { mount } from '@vue/test-utils'
import CurrencyInput from '@/components/CurrencyInput.vue'
describe('CurrencyInput.vue', () => {
it("changing the element's value, updates the v-model", () => {
var parent = mount({
data: { price: null },
template: '<div> <currency-input v-model="price"></currency-input> </div>',
components: { 'currency-input': CurrencyInput }
})
var currencyInputInnerTextField = parent.find('input');
currencyInputInnerTextField.element.value = 13.467;
currencyInputInnerTextField.trigger('input');
expect(parent.vm.price).toBe(13.46);
});
});
var CurrencyInput = Vue.component('currency-input', {
template: '\
<span>\
$\
<input\
ref="input"\
v-bind:value="value"\
v-on:input="updateValue($event.target.value)">\
</span>\
',
props: ['value'],
methods: {
// Instead of updating the value directly, this
// method is used to format and place constraints
// on the input's value
updateValue: function(value) {
var formattedValue = value
// Remove whitespace on either side
.trim()
// Shorten to 2 decimal places
.slice(0, value.indexOf('.') === -1 ? value.length : value.indexOf('.') + 3)
// If the value was not already normalized,
// manually override it to conform
if (formattedValue !== value) {
this.$refs.input.value = formattedValue
}
// Emit the number value through the input event
this.$emit('input', Number(formattedValue))
}
}
});
// specs code ///////////////////////////////////////////////////////////
var mount = vueTestUtils.mount;
describe('CurrencyInput', () => {
it("changing the element's value, updates the v-model", () => {
var parent = mount({
data() { return { price: null } },
template: '<div> <currency-input v-model="price"></currency-input> </div>',
components: { 'currency-input': CurrencyInput }
});
var currencyInputInnerTextField = parent.find('input');
currencyInputInnerTextField.element.value = 13.467;
currencyInputInnerTextField.trigger('input');
expect(parent.vm.price).toBe(13.46);
});
});
// load jasmine htmlReporter
(function() {
var env = jasmine.getEnv()
env.addReporter(new jasmine.HtmlReporter())
env.execute()
}())
<link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/jasmine/1.3.1/jasmine.css">
<script src="https://cdn.jsdelivr.net/jasmine/1.3.1/jasmine.js"></script>
<script src="https://cdn.jsdelivr.net/jasmine/1.3.1/jasmine-html.js"></script>
<script src="https://npmcdn.com/[email protected]/dist/vue.js"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/browser.js"></script>
<script src="https://rawgit.com/vuejs/vue-test-utils/2b078c68293a41d68a0a98393f497d0b0031f41a/dist/vue-test-utils.iife.js"></script>
Note: The code above works fine (as you can see), but there can be improvements to tests involving v-model
soon. Follow this issue for up-to-date info.