Add another test

testsuite/gsk/compare/blend-modes.node

@@ -0,0 +1,23 @@
+blend {
+  mode: difference;
+  bottom: color {
+    bounds: 0 0 100 100;
+    color: red;
+  }
+  top: color {
+    bounds: 50 50 100 100;
+    color: blue;
+  }
+}
+
+blend {
+  mode: normal;
+  bottom: color {
+    bounds: 150 0 100 100;
+    color: red;
+  }
+  top: color {
+    bounds: 200 50 100 100;
+    color: blue;
+  }
+}

testsuite/gsk/meson.build

@@ -15,6 +15,7 @@ compare_render_tests = [
   'big-checkerboard-scaled-down-nearest',
   'big-checkerboard-scaled-down2',
   'blend-difference',
+  'blend-modes',
   'blend-invisible-child',
   'blend-normal',
   'border-bottom-right',