Add failing test coverage

osu.Game.Tests/Mods/ModDifficultyAdjustTest.cs

@@ -8,6 +8,8 @@ using osu.Game.Online.API;
 using osu.Game.Rulesets;
 using osu.Game.Rulesets.Difficulty;
 using osu.Game.Rulesets.Mods;
+using osu.Game.Rulesets.Osu;
+using osu.Game.Rulesets.Osu.Mods;
 using osu.Game.Rulesets.UI;
 
 namespace osu.Game.Tests.Mods
@@ -105,9 +107,6 @@ namespace osu.Game.Tests.Mods
             testMod.ResetSettingsToDefaults();
 
             Assert.That(testMod.DrainRate.Value, Is.Null);
-
-            // ReSharper disable once HeuristicUnreachableCode
-            // see https://youtrack.jetbrains.com/issue/RIDER-70159.
             Assert.That(testMod.OverallDifficulty.Value, Is.Null);
 
             var applied = applyDifficulty(new BeatmapDifficulty
@@ -119,6 +118,48 @@ namespace osu.Game.Tests.Mods
             Assert.That(applied.OverallDifficulty, Is.EqualTo(10));
         }
 
+        [Test]
+        public void TestDeserializeIncorrectRange()
+        {
+            var apiMod = new APIMod
+            {
+                Acronym = @"DA",
+                Settings = new Dictionary<string, object>
+                {
+                    [@"circle_size"] = -727,
+                    [@"approach_rate"] = -727,
+                }
+            };
+            var ruleset = new OsuRuleset();
+
+            var mod = (OsuModDifficultyAdjust)apiMod.ToMod(ruleset);
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(mod.CircleSize.Value, Is.GreaterThanOrEqualTo(0).And.LessThanOrEqualTo(11));
+                Assert.That(mod.ApproachRate.Value, Is.GreaterThanOrEqualTo(-10).And.LessThanOrEqualTo(11));
+            });
+        }
+
+        [Test]
+        public void TestDeserializeNegativeApproachRate()
+        {
+            var apiMod = new APIMod
+            {
+                Acronym = @"DA",
+                Settings = new Dictionary<string, object>
+                {
+                    [@"approach_rate"] = -9,
+                }
+            };
+            var ruleset = new OsuRuleset();
+
+            var mod = (OsuModDifficultyAdjust)apiMod.ToMod(ruleset);
+
+            Assert.That(mod.ApproachRate.Value, Is.GreaterThanOrEqualTo(-10).And.LessThanOrEqualTo(11));
+            Assert.That(mod.ApproachRate.Value, Is.EqualTo(-9));
+        }
+
         /// <summary>
         /// Applies a <see cref="BeatmapDifficulty"/> to the mod and returns a new <see cref="BeatmapDifficulty"/>
         /// representing the result if the mod were applied to a fresh <see cref="BeatmapDifficulty"/> instance.

osu.Game.Tests/Visual/UserInterface/TestSceneModDifficultyAdjustSettings.cs

@@ -70,7 +70,7 @@ namespace osu.Game.Tests.Visual.UserInterface
         }
 
         [Test]
-        public void TestOutOfRangeValueStillApplied()
+        public void TestValueAboveRangeStillApplied()
         {
             AddStep("set override cs to 11", () => modDifficultyAdjust.CircleSize.Value = 11);
 
@@ -91,6 +91,28 @@ namespace osu.Game.Tests.Visual.UserInterface
             checkBindableAtValue("Circle Size", 11);
         }
 
+        [Test]
+        public void TestValueBelowRangeStillApplied()
+        {
+            AddStep("set override cs to -5", () => modDifficultyAdjust.ApproachRate.Value = -5);
+
+            checkSliderAtValue("Approach Rate", -5);
+            checkBindableAtValue("Approach Rate", -5);
+
+            // this is a no-op, just showing that it won't reset the value during deserialisation.
+            setExtendedLimits(false);
+
+            checkSliderAtValue("Approach Rate", -5);
+            checkBindableAtValue("Approach Rate", -5);
+
+            // setting extended limits will reset the serialisation exception.
+            // this should be fine as the goal is to allow, at most, the value of extended limits.
+            setExtendedLimits(true);
+
+            checkSliderAtValue("Approach Rate", -5);
+            checkBindableAtValue("Approach Rate", -5);
+        }
+
         [Test]
         public void TestExtendedLimits()
         {
@@ -109,6 +131,11 @@ namespace osu.Game.Tests.Visual.UserInterface
             checkSliderAtValue("Circle Size", 11);
             checkBindableAtValue("Circle Size", 11);
 
+            setSliderValue("Approach Rate", -5);
+
+            checkSliderAtValue("Approach Rate", -5);
+            checkBindableAtValue("Approach Rate", -5);
+
             setExtendedLimits(false);
 
             checkSliderAtValue("Circle Size", 10);