Replaces tile.tests.js (partially) with new tests

Transforms the old rendering tests for the TileLayer
to the new rendering test approach.
The render-listener test is kept in the old format for know.

rendering/cases/layer-tile-opacity/main.js

@@ -0,0 +1,26 @@
+import Map from '../../../src/ol/Map.js';
+import View from '../../../src/ol/View.js';
+import TileLayer from '../../../src/ol/layer/Tile.js';
+import {fromLonLat} from '../../../src/ol/proj';
+import XYZ from '../../../src/ol/source/XYZ';
+
+const center = fromLonLat([8.6, 50.1]);
+
+new Map({
+  layers: [
+    new TileLayer({
+      source: new XYZ({
+        url: '/data/tiles/satellite/{z}/{x}/{y}.jpg',
+        transition: 0
+      }),
+      opacity: 0.2
+    })
+  ],
+  target: 'map',
+  view: new View({
+    center: center,
+    zoom: 3
+  })
+});
+
+render();