replace jest with ava

node_modules/ava/lib/extensions.js

@@ -0,0 +1,43 @@
+module.exports = (configuredExtensions, providers = []) => {
+	// Combine all extensions possible for testing. Remove duplicate extensions.
+	const duplicates = new Set();
+	const seen = new Set();
+	const combine = extensions => {
+		for (const ext of extensions) {
+			if (seen.has(ext)) {
+				duplicates.add(ext);
+			} else {
+				seen.add(ext);
+			}
+		}
+	};
+
+	if (configuredExtensions !== undefined) {
+		combine(configuredExtensions);
+	}
+
+	for (const {main} of providers) {
+		combine(main.extensions);
+	}
+
+	if (duplicates.size > 0) {
+		throw new Error(`Unexpected duplicate extensions in options: ’${[...duplicates].join('’, ’')}’.`);
+	}
+
+	// Unless the default was used by providers, as long as the extensions aren't explicitly set, set the default.
+	if (configuredExtensions === undefined) {
+		if (!seen.has('cjs')) {
+			seen.add('cjs');
+		}
+
+		if (!seen.has('mjs')) {
+			seen.add('mjs');
+		}
+
+		if (!seen.has('js')) {
+			seen.add('js');
+		}
+	}
+
+	return [...seen];
+};