Add unit test asserting that saving, loading & saving the map produces identical output. (#348)

Also fixed PowerProvider violating this.

Content.IntegrationTests/SaveLoadSaveTest.cs

@@ -0,0 +1,54 @@
+using System.IO;
+using System.Threading.Tasks;
+using NUnit.Framework;
+using Robust.Server.Interfaces.Maps;
+using Robust.Shared.Interfaces.Map;
+using Robust.Shared.Interfaces.Resources;
+using Robust.Shared.Map;
+using Robust.Shared.Utility;
+
+namespace Content.IntegrationTests
+{
+    /// <summary>
+    ///     Tests that the
+    /// </summary>
+    [TestFixture]
+    public class SaveLoadSaveTest : ContentIntegrationTest
+    {
+        [Test]
+        public async Task SaveLoadSave()
+        {
+            var server = StartServer();
+            await server.WaitIdleAsync();
+            var mapLoader = server.ResolveDependency<IMapLoader>();
+            var mapManager = server.ResolveDependency<IMapManager>();
+            server.Post(() =>
+            {
+                mapLoader.SaveBlueprint(new GridId(2), "save load save 1.yml");
+                var map = mapManager.CreateMap();
+                var grid = mapLoader.LoadBlueprint(map, "save load save 1.yml");
+                mapLoader.SaveBlueprint(grid.Index, "save load save 2.yml");
+            });
+
+            await server.WaitIdleAsync();
+            var userData = server.ResolveDependency<IResourceManager>().UserData;
+
+            string one;
+            string two;
+
+            using (var stream = userData.Open(new ResourcePath("save load save 1.yml"), FileMode.Open))
+            using (var reader = new StreamReader(stream))
+            {
+                one = reader.ReadToEnd();
+            }
+
+            using (var stream = userData.Open(new ResourcePath("save load save 2.yml"), FileMode.Open))
+            using (var reader = new StreamReader(stream))
+            {
+                two = reader.ReadToEnd();
+            }
+
+            Assert.That(one, Is.EqualTo(two));
+        }
+    }
+}