m->d: Emoji sprite sheet supports APNG

m2d/converters/emoji-sheet.test.js

@@ -0,0 +1,55 @@
+const assert = require("assert").strict
+const {test} = require("supertape")
+const {_convertImageStream} = require("./emoji-sheet")
+const fetch = require("node-fetch")
+const {Transform} = require("stream").Transform
+
+/* c8 ignore next 7 */
+function slow() {
+	if (process.argv.includes("--slow")) {
+		return test
+	} else {
+		return test.skip
+	}
+}
+
+class Meter extends Transform {
+	bytes = 0
+
+	_transform(chunk, encoding, cb) {
+		this.bytes += chunk.length
+		this.push(chunk)
+		cb()
+	}
+}
+
+/**
+ * @param {import("supertape").Test} t
+ * @param {string} url
+ * @param {number} totalSize
+ */
+async function runSingleTest(t, url, totalSize) {
+	const abortController = new AbortController()
+	const res = await fetch("https://ezgif.com/images/format-demo/butterfly.png", {agent: false, signal: abortController.signal})
+	const meter = new Meter()
+	const p = res.body.pipe(meter)
+	const result = await _convertImageStream(p, () => {
+		abortController.abort()
+		res.body.pause()
+		res.body.emit("end")
+	})
+	t.equal(result.subarray(1, 4).toString("ascii"), "PNG", `result was not a PNG file: ${result.toString("base64")}`)
+	if (meter.bytes < totalSize / 4) { // should download less than 25% of each file
+		t.pass("intentionally read partial file")
+	} else {
+		t.fail(`read more than 25% of file, read: ${meter.bytes}, total: ${totalSize}`)
+	}
+}
+
+slow()("emoji-sheet: only partial file is read for APNG", async t => {
+	await runSingleTest(t, "https://ezgif.com/images/format-demo/butterfly.png", 2438998)
+})
+
+slow()("emoji-sheet: only partial file is read for GIF", async t => {
+	await runSingleTest(t, "https://ezgif.com/images/format-demo/butterfly.gif", 781223)
+})