Testing

Unit-test reactive and wasmwrap bindings with jsdom — no browser, no headless driver.

GOOS=js GOARCH=wasm go test runs under node, which has no DOM. The jsdom package is a small fake DOM that astwerk's own tests run against, exported so yours can too.

Documentation

Install

//go:build js && wasm

package main

import "github.com/LukasDerBaum42/astwerk/jsdom"

func init() { jsdom.Install() }

Install defines document, location, history and requestAnimationFrame on globalThis; calling it twice is harmless.

Reset and NewElement

func TestCounterIncrements(t *testing.T) {
	jsdom.Reset() // a clean document.body for this test
	root := wasmwrap.Wrap(jsdom.NewElement("div"))
	// mount your bindings into root, then assert against it
}

Reset restores a clean document between tests. NewElement makes a detached element to mount bindings into.

Running the tests

export PATH="$PATH:$(go env GOROOT)/lib/wasm"
GOOS=js GOARCH=wasm go test ./...

The toolchain's own wasm runner needs to be on PATH. The build constraint on your test file keeps it out of ordinary host builds.

What the fake DOM implements

elements: tagName, children, appendChild, insertBefore, remove, cloneNode, textContent, innerHTML, attributes, classList, style, value/checked, getBoundingClientRect;
selectors, limited to #id, .class, [attr] and a bare tag name, for querySelector, querySelectorAll and closest;
events: addEventListener, removeEventListener, and a dispatch helper;
a 2D canvas context that records its calls;
location, history and requestAnimationFrame, so the router has something to drive.

And extras a real DOM doesn't have, for assertions:

el.listenerCount(type)  // number of handlers bound for an event
el._tree                // comma-joined text of the subtree, for list ordering
el._rect                // the object getBoundingClientRect returns
el.dispatch(type, prop) // fire an event with extra properties
el._ctxCalls            // recorded 2D canvas calls, as "fillRect(1,2,3,4)"

It's not a browser and it will never grow into one — layout, the CSS cascade, focus and paint are out of scope by design. It answers "did my Go code reach for the right property with the right arguments", which is the question a binding test is actually asking. Anything that only a real DOM can settle needs a real browser.

Example

//go:build js && wasm

package main

import (
	"strconv"
	"testing"

	"github.com/LukasDerBaum42/astwerk/jsdom"
	"github.com/LukasDerBaum42/astwerk/reactive"
	"github.com/LukasDerBaum42/astwerk/wasmwrap"
)

func init() { jsdom.Install() }

func TestCounterIncrements(t *testing.T) {
	jsdom.Reset()
	root := wasmwrap.Wrap(jsdom.NewElement("div"))

	count := reactive.NewSignal(0)
	label := wasmwrap.Create("span")
	reactive.BindText(label, func() string { return strconv.Itoa(count.Get()) })
	root.Append(label)

	count.Set(3)
	if got := label.Text(); got != "3" {
		t.Errorf("label = %q, want \"3\"", got)
	}
}

A signal, a binding, a write, an assertion — no browser, no headless driver, no separate test runner.