Add app icon, security hardening, logout, screenshots, unit tests

- Custom app icon (dark circle + glucose wave + live dot)
- Security: DPAPI entropy, config ACL restriction, input validation/clamping
- Logout / Clear Credentials context menu option
- 105 xUnit tests covering models, settings sanitization, API parsing
- CI workflow updated to run tests before publish
- Screenshots and README updates

Author: Keith Klein

.github/workflows/release.yml

@@ -24,6 +24,9 @@ jobs:
       - name: Restore dependencies
         run: dotnet restore DexcomOverlay/DexcomOverlay.csproj
 
+      - name: Run tests
+        run: dotnet test DexcomOverlay.Tests/DexcomOverlay.Tests.csproj --configuration Release --verbosity normal
+
       - name: Publish
         run: >
           dotnet publish DexcomOverlay/DexcomOverlay.csproj

DexcomOverlay.Tests/DexcomOverlay.Tests.csproj

@@ -0,0 +1,28 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0-windows10.0.19041.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <UseWPF>true</UseWPF>
+
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+    <PackageReference Include="xunit" Version="2.5.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\DexcomOverlay\DexcomOverlay.csproj" />
+  </ItemGroup>
+
+</Project>

DexcomOverlay.Tests/Models/AppSettingsTests.cs

@@ -0,0 +1,45 @@
+using DexcomOverlay.Models;
+
+namespace DexcomOverlay.Tests.Models;
+
+public class AppSettingsTests
+{
+    [Fact]
+    public void Defaults_HaveExpectedValues()
+    {
+        var settings = new AppSettings();
+
+        Assert.Equal("", settings.Username);
+        Assert.Equal("", settings.Password);
+        Assert.Equal("us", settings.Region);
+        Assert.Null(settings.WindowX);
+        Assert.Null(settings.WindowY);
+        Assert.Equal(60, settings.RefreshIntervalSeconds);
+        Assert.Equal(48, settings.FontSize);
+        Assert.Equal(0.9, settings.Opacity);
+        Assert.True(settings.ShowTrendArrow);
+        Assert.False(settings.ShowMmol);
+        Assert.True(settings.EnablePredictiveAlerts);
+        Assert.Equal(15, settings.AlertCooldownMinutes);
+    }
+
+    [Fact]
+    public void Thresholds_HaveDefaults()
+    {
+        var t = new GlucoseThresholds();
+
+        Assert.Equal(55, t.UrgentLow);
+        Assert.Equal(70, t.Low);
+        Assert.Equal(180, t.High);
+        Assert.Equal(250, t.UrgentHigh);
+    }
+
+    [Fact]
+    public void Thresholds_AreInOrder()
+    {
+        var t = new GlucoseThresholds();
+        Assert.True(t.UrgentLow < t.Low);
+        Assert.True(t.Low < t.High);
+        Assert.True(t.High < t.UrgentHigh);
+    }
+}

DexcomOverlay.Tests/Models/GlucoseReadingTests.cs

@@ -0,0 +1,113 @@
+using DexcomOverlay.Models;
+
+namespace DexcomOverlay.Tests.Models;
+
+public class GlucoseReadingTests
+{
+    // ── MmolL conversion ───────────────────────────────────────
+
+    [Theory]
+    [InlineData(100, 5.6)]   // 100 mg/dL → 5.6 mmol/L
+    [InlineData(180, 10.0)]  // 180 mg/dL → 10.0 mmol/L
+    [InlineData(70, 3.9)]    // 70 mg/dL  → 3.9 mmol/L
+    [InlineData(55, 3.1)]    // 55 mg/dL  → 3.1 mmol/L
+    [InlineData(250, 13.9)]  // 250 mg/dL → 13.9 mmol/L
+    [InlineData(0, 0.0)]     // edge: zero
+    public void MmolL_ConvertsCorrectly(int mgdl, double expectedMmol)
+    {
+        var reading = new GlucoseReading { Value = mgdl };
+        Assert.Equal(expectedMmol, reading.MmolL);
+    }
+
+    // ── Trend arrows ───────────────────────────────────────────
+
+    [Theory]
+    [InlineData(0, "")]     // None
+    [InlineData(1, "↑↑")]  // DoubleUp
+    [InlineData(2, "↑")]   // SingleUp
+    [InlineData(3, "↗")]   // FortyFiveUp
+    [InlineData(4, "→")]   // Flat
+    [InlineData(5, "↘")]   // FortyFiveDown
+    [InlineData(6, "↓")]   // SingleDown
+    [InlineData(7, "↓↓")]  // DoubleDown
+    [InlineData(8, "?")]   // NotComputable
+    [InlineData(9, "-")]   // RateOutOfRange
+    public void TrendArrow_ReturnsCorrectSymbol(int trendIndex, string expectedArrow)
+    {
+        var reading = new GlucoseReading { TrendIndex = trendIndex };
+        Assert.Equal(expectedArrow, reading.TrendArrow);
+    }
+
+    [Fact]
+    public void TrendArrow_OutOfRange_ReturnsFallback()
+    {
+        var reading = new GlucoseReading { TrendIndex = 99 };
+        Assert.Equal("→", reading.TrendArrow); // default fallback
+    }
+
+    // ── Trend descriptions ─────────────────────────────────────
+
+    [Theory]
+    [InlineData(0, "")]
+    [InlineData(1, "rising quickly")]
+    [InlineData(4, "steady")]
+    [InlineData(7, "falling quickly")]
+    [InlineData(8, "unable to determine")]
+    [InlineData(9, "trend unavailable")]
+    public void TrendDescription_ReturnsCorrectText(int trendIndex, string expected)
+    {
+        var reading = new GlucoseReading { TrendIndex = trendIndex };
+        Assert.Equal(expected, reading.TrendDescription);
+    }
+
+    [Fact]
+    public void TrendDescription_OutOfRange_ReturnsFallback()
+    {
+        var reading = new GlucoseReading { TrendIndex = -1 };
+        Assert.Equal("steady", reading.TrendDescription);
+    }
+
+    // ── TrendDirectionMap ──────────────────────────────────────
+
+    [Theory]
+    [InlineData("None", 0)]
+    [InlineData("DoubleUp", 1)]
+    [InlineData("SingleUp", 2)]
+    [InlineData("FortyFiveUp", 3)]
+    [InlineData("Flat", 4)]
+    [InlineData("FortyFiveDown", 5)]
+    [InlineData("SingleDown", 6)]
+    [InlineData("DoubleDown", 7)]
+    [InlineData("NotComputable", 8)]
+    [InlineData("RateOutOfRange", 9)]
+    public void TrendDirectionMap_ContainsAllDirections(string direction, int expectedIndex)
+    {
+        Assert.True(GlucoseReading.TrendDirectionMap.ContainsKey(direction));
+        Assert.Equal(expectedIndex, GlucoseReading.TrendDirectionMap[direction]);
+    }
+
+    [Fact]
+    public void TrendDirectionMap_IsCaseInsensitive()
+    {
+        Assert.True(GlucoseReading.TrendDirectionMap.ContainsKey("flat"));
+        Assert.True(GlucoseReading.TrendDirectionMap.ContainsKey("FLAT"));
+        Assert.True(GlucoseReading.TrendDirectionMap.ContainsKey("Flat"));
+    }
+
+    [Fact]
+    public void TrendDirectionMap_Has10Entries()
+    {
+        Assert.Equal(10, GlucoseReading.TrendDirectionMap.Count);
+    }
+
+    // ── Default values ─────────────────────────────────────────
+
+    [Fact]
+    public void Defaults_AreReasonable()
+    {
+        var reading = new GlucoseReading();
+        Assert.Equal(0, reading.Value);
+        Assert.Equal("Flat", reading.TrendDirection);
+        Assert.Equal(0, reading.TrendIndex);
+    }
+}