Tests: xUnit project with HAR fixtures (50 tests); fix relative delivery/HLS URLs resolving to file:// on Linux

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Jellyfin.Plugin.Floatplane.Tests/DeliveryResolverTests.cs

@@ -0,0 +1,69 @@
+using System;
+using System.Linq;
+using Jellyfin.Plugin.Floatplane.Api.Models;
+using Jellyfin.Plugin.Floatplane.Playback;
+using Xunit;
+
+namespace Jellyfin.Plugin.Floatplane.Tests;
+
+public class DeliveryResolverTests
+{
+    private static ResolvedVariant[] Variants() => Fixture.Json<DeliveryInfoModel>("delivery-info.json").Resolve().ToArray();
+
+    [Fact]
+    public void SelectVariant_exact_level()
+    {
+        var v = DeliveryResolver.SelectVariant(Variants(), "720");
+
+        Assert.NotNull(v);
+        Assert.Equal("720-avc1", v!.Name);
+    }
+
+    [Fact]
+    public void SelectVariant_falls_back_to_not_taller()
+    {
+        // 2160 is denied → best usable ≤ 2160 is 1080
+        var v = DeliveryResolver.SelectVariant(Variants(), "2160");
+
+        Assert.Equal("1080-avc1", v!.Name);
+
+        var v2 = DeliveryResolver.SelectVariant(Variants(), "600");
+        Assert.Equal("480-avc1", v2!.Name);
+    }
+
+    [Fact]
+    public void SelectVariant_falls_back_to_best_when_nothing_fits()
+    {
+        var v = DeliveryResolver.SelectVariant(Variants(), "240");
+
+        Assert.Equal("1080-avc1", v!.Name);
+    }
+
+    [Fact]
+    public void SelectVariant_returns_null_without_usable_variants()
+    {
+        var disabled = Variants().Select(v => new ResolvedVariant(new DeliveryVariant { Name = v.Name, Url = string.Empty, Enabled = false }, v.Url)).ToList();
+
+        Assert.Null(DeliveryResolver.SelectVariant(disabled, "1080"));
+        Assert.Null(DeliveryResolver.SelectVariant(Array.Empty<ResolvedVariant>(), "1080"));
+    }
+
+    [Fact]
+    public void TokenExpiry_reads_exp_from_jwt()
+    {
+        var url = Variants().First(v => v.Height == 1080).Url;
+
+        var exp = DeliveryResolver.TokenExpiry(url);
+
+        Assert.Equal(DateTimeOffset.FromUnixTimeSeconds(1792935296), exp);
+    }
+
+    [Theory]
+    [InlineData("https://cdn.example/x.m3u8")]
+    [InlineData("https://cdn.example/x.m3u8?token=not-a-jwt")]
+    [InlineData("not a url")]
+    public void TokenExpiry_returns_null_without_jwt(string url)
+    {
+        Assert.Null(DeliveryResolver.TokenExpiry(url));
+    }
+}