added tests to project

CursorLang.Tests/Models/AppSettingsTests.cs

@@ -0,0 +1,165 @@
+using System.ComponentModel;
+using System.Reflection;
+using System.Text.Json;
+using System.Windows.Media;
+using CursorLang.Models;
+
+namespace CursorLang.Tests.Models;
+
+public sealed class AppSettingsTests
+{
+    [Fact]
+    public void Default_values_describe_a_tooltip_at_the_cursor()
+    {
+        var settings = new AppSettings();
+
+        Assert.Equal("en", settings.Language);
+        Assert.Equal(AppTheme.System, settings.Theme);
+        Assert.Equal(PopupPlacementMode.AtCursor, settings.PlacementMode);
+        Assert.Equal(AnchorSide.BottomRight, settings.CursorSide);
+        Assert.Equal(16, settings.CursorOffset);
+        Assert.Equal(AnchorSide.BottomRight, settings.CaretSide);
+        Assert.Equal(16, settings.CaretOffset);
+        Assert.Equal(ScreenPosition.BottomRight, settings.ScreenPosition);
+        Assert.Equal(24, settings.ScreenMargin);
+        Assert.Equal(20, settings.FontSize);
+        Assert.Equal(0.9, settings.Opacity);
+        Assert.Equal(500, settings.DurationMilliseconds);
+        Assert.Equal(300, settings.CapsLockHoldMilliseconds);
+        Assert.Equal(Color.FromRgb(0x20, 0x20, 0x20), settings.BackgroundColor);
+        Assert.Equal(Color.FromRgb(0xFF, 0xFF, 0xFF), settings.ForegroundColor);
+    }
+
+    // The app must not change how the system behaves until it is asked to
+    [Fact]
+    public void Caps_Lock_interception_is_off_by_default()
+    {
+        Assert.False(new AppSettings().UseCapsLockHotkey);
+    }
+
+    [Fact]
+    public void The_time_on_screen_is_derived_from_milliseconds()
+    {
+        var settings = new AppSettings { DurationMilliseconds = 1250 };
+
+        Assert.Equal(TimeSpan.FromMilliseconds(1250), settings.Duration);
+    }
+
+    [Fact]
+    public void The_hold_threshold_is_derived_from_milliseconds()
+    {
+        var settings = new AppSettings { CapsLockHoldMilliseconds = 400 };
+
+        Assert.Equal(TimeSpan.FromMilliseconds(400), settings.CapsLockHoldDelay);
+    }
+
+    [Theory]
+    [MemberData(nameof(WritableProperties))]
+    public void A_changed_setting_is_announced_to_subscribers(string propertyName)
+    {
+        var settings = new AppSettings();
+        List<string?> changed = [];
+        settings.PropertyChanged += (_, e) => changed.Add(e.PropertyName);
+
+        SetDifferentValue(settings, propertyName);
+
+        Assert.Contains(propertyName, changed);
+    }
+
+    [Theory]
+    [MemberData(nameof(WritableProperties))]
+    public void Writing_the_same_value_leaves_subscribers_alone(string propertyName)
+    {
+        var settings = new AppSettings();
+        PropertyInfo property = typeof(AppSettings).GetProperty(propertyName)!;
+        object? value = property.GetValue(settings);
+
+        List<string?> changed = [];
+        settings.PropertyChanged += (_, e) => changed.Add(e.PropertyName);
+
+        property.SetValue(settings, value);
+
+        Assert.Empty(changed);
+    }
+
+    // Duration and CapsLockHoldDelay are derived from other settings and have
+    // no business being in the file
+    [Fact]
+    public void Derived_values_stay_out_of_the_file()
+    {
+        using JsonDocument document = JsonSerializer.SerializeToDocument(new AppSettings());
+
+        List<string> names = [.. document.RootElement.EnumerateObject().Select(property => property.Name)];
+
+        Assert.DoesNotContain(nameof(AppSettings.Duration), names);
+        Assert.DoesNotContain(nameof(AppSettings.CapsLockHoldDelay), names);
+
+        // What they are derived from, on the other hand, has to be stored
+        Assert.Contains(nameof(AppSettings.DurationMilliseconds), names);
+        Assert.Contains(nameof(AppSettings.CapsLockHoldMilliseconds), names);
+    }
+
+    [Fact]
+    public void Settings_report_changes_as_INotifyPropertyChanged()
+    {
+        Assert.IsAssignableFrom<INotifyPropertyChanged>(new AppSettings());
+    }
+
+    public static TheoryData<string> WritableProperties()
+    {
+        var data = new TheoryData<string>();
+
+        foreach (string name in WritablePropertyNames())
+        {
+            data.Add(name);
+        }
+
+        return data;
+    }
+
+    /// <summary>Names of the settings the user is able to change.</summary>
+    internal static IEnumerable<string> WritablePropertyNames() =>
+        typeof(AppSettings).GetProperties()
+            .Where(property => property.CanWrite)
+            .Select(property => property.Name);
+
+    // A value guaranteed to differ from the current one: each kind of setting
+    // has its own way of differing
+    private static void SetDifferentValue(AppSettings settings, string propertyName)
+    {
+        PropertyInfo property = typeof(AppSettings).GetProperty(propertyName)!;
+        object? current = property.GetValue(settings);
+
+        object next = current switch
+        {
+            string text => text + "-other",
+            double number => number + 1,
+            bool flag => !flag,
+            Color color => Color.FromRgb((byte)(color.R + 1), color.G, color.B),
+            Enum value => NextEnumValue(value),
+            DateTimeOffset moment => moment.AddDays(1),
+
+            // A setting never set yet: the app has not checked for updates once
+            null when property.PropertyType == typeof(DateTimeOffset?) => DateTimeOffset.UnixEpoch,
+
+            _ => throw new NotSupportedException($"Unknown kind of setting: {property.PropertyType}"),
+        };
+
+        property.SetValue(settings, next);
+    }
+
+    private static object NextEnumValue(Enum current)
+    {
+        Array values = Enum.GetValues(current.GetType());
+
+        foreach (object? value in values)
+        {
+            if (!Equals(value, current))
+            {
+                return value!;
+            }
+        }
+
+        throw new NotSupportedException($"{current.GetType()} has a single value");
+    }
+}