Test mergeImages returns empty b64 string if nothing is passed in

test/unit.js

@@ -0,0 +1,8 @@
+import test from 'ava';
+import Canvas from 'canvas';
+import mergeImages from '../';
+
+test('mergeImages returns empty b64 string if nothing is passed in', async t => {
+	t.plan(1);
+	await mergeImages([], { Canvas }).then(b64 => t.is(b64, 'data:,'));
+});