Disease Stages But Epic (#9043)

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>
Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.IntegrationTests/Tests/DiseaseTest.cs

@@ -0,0 +1,48 @@
+using System.Threading.Tasks;
+using Content.Shared.Disease;
+using NUnit.Framework;
+using Robust.Shared.Prototypes;
+
+namespace Content.IntegrationTests.Tests;
+
+[TestFixture]
+public sealed class DiseaseTest
+{
+    /// <summary>
+    /// Asserts that a disease prototype has valid stages for its effects and cures.
+    /// </summary>
+    [Test]
+    public async Task Stages()
+    {
+        await using var pairTracker = await PoolManager.GetServerClient(new PoolSettings{NoClient = true});
+        var server = pairTracker.Pair.Server;
+
+        var protoManager = server.ResolveDependency<IPrototypeManager>();
+
+        await server.WaitAssertion(() =>
+        {
+            foreach (var proto in protoManager.EnumeratePrototypes<DiseasePrototype>())
+            {
+                var stages = proto.Stages;
+
+                foreach (var effect in proto.Effects)
+                {
+                    for (var i = 0; i < effect.Stages.Length; i++)
+                    {
+                        Assert.That(stages.Contains(i), $"Disease {proto.ID} has an effect with an incorrect stage, {i}!");
+                    }
+                }
+
+                foreach (var cure in proto.Cures)
+                {
+                    for (var i = 0; i < cure.Stages.Length; i++)
+                    {
+                        Assert.That(stages.Contains(i), $"Disease {proto.ID} has a cure with an incorrect stage, {i}!");
+                    }
+                }
+            }
+        });
+
+        await pairTracker.CleanReturnAsync();
+    }
+}