Move all TestCases to Testing project

This allows tests to successfully retrieve rulesets, as they are referenced.

osu.Game.Tests/Visual/TestCaseMods.cs

@@ -0,0 +1,56 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Game.Overlays.Mods;
+using osu.Game.Rulesets;
+using osu.Game.Screens.Play.HUD;
+using OpenTK;
+
+namespace osu.Game.Tests.Visual
+{
+    internal class TestCaseMods : OsuTestCase
+    {
+        public override string Description => @"Mod select overlay and in-game display";
+
+        private ModSelectOverlay modSelect;
+        private ModDisplay modDisplay;
+
+        private RulesetStore rulesets;
+
+
+        [BackgroundDependencyLoader]
+        private void load(RulesetStore rulesets)
+        {
+            this.rulesets = rulesets;
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            Add(modSelect = new ModSelectOverlay
+            {
+                RelativeSizeAxes = Axes.X,
+                Origin = Anchor.BottomCentre,
+                Anchor = Anchor.BottomCentre,
+            });
+
+            Add(modDisplay = new ModDisplay
+            {
+                Anchor = Anchor.TopRight,
+                Origin = Anchor.TopRight,
+                AutoSizeAxes = Axes.Both,
+                Position = new Vector2(0, 25),
+            });
+
+            modDisplay.Current.BindTo(modSelect.SelectedMods);
+
+            AddStep("Toggle", modSelect.ToggleVisibility);
+
+            foreach (var ruleset in rulesets.AvailableRulesets)
+                AddStep(ruleset.CreateInstance().Description, () => modSelect.Ruleset.Value = ruleset);
+        }
+    }
+}