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Co-authored-by: Cursor <cursoragent@cursor.com>

tests/HSchool.AppHost.Tests/ChangelogApiTests.cs

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+using System.Net.Http.Json;
+using System.Text.Json;
+using System.Text.RegularExpressions;
+
+namespace HSchool.AppHost.Tests;
+
+[Collection(AppHostCollection.Name)]
+public class ChangelogApiTests(AppHostFixture fixture)
+{
+    private static readonly Regex Sha = new("^[0-9a-f]{40}$", RegexOptions.CultureInvariant);
+
+    [Fact]
+    public async Task Changelog_WithoutSession_ReturnsUnauthorized()
+    {
+        var http = fixture.App.GetEndpoint("server", "http").ToString();
+        using var client = new HttpClient { BaseAddress = new Uri(http) };
+
+        using var response = await client.GetAsync("/api/changelog", TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Changelog_WithoutSince_ReturnsCurrentAndEmptyCommits()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        await SchoolApiTests.LoginAsync(client);
+
+        var body = await client.GetFromJsonAsync<ChangelogDto>(
+            "/api/changelog",
+            JsonOptions,
+            TestContext.Current.CancellationToken);
+
+        Assert.NotNull(body);
+        Assert.Matches(Sha, body.Current);
+        Assert.Empty(body.Commits);
+    }
+
+    [Fact]
+    public async Task Changelog_SinceCurrent_ReturnsEmptyCommits()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        await SchoolApiTests.LoginAsync(client);
+
+        var first = await client.GetFromJsonAsync<ChangelogDto>(
+            "/api/changelog",
+            JsonOptions,
+            TestContext.Current.CancellationToken);
+        Assert.NotNull(first);
+
+        var again = await client.GetFromJsonAsync<ChangelogDto>(
+            $"/api/changelog?since={first.Current}",
+            JsonOptions,
+            TestContext.Current.CancellationToken);
+
+        Assert.NotNull(again);
+        Assert.Equal(first.Current, again.Current);
+        Assert.Empty(again.Commits);
+    }
+
+    private static JsonSerializerOptions JsonOptions { get; } = new()
+    {
+        PropertyNameCaseInsensitive = true,
+    };
+
+    private sealed record ChangelogDto(string Current, ChangelogCommitDto[] Commits);
+
+    private sealed record ChangelogCommitDto(string Sha, DateTimeOffset Date, string Subject);
+}

tests/HSchool.Server.Tests/BuildChangelogTests.cs

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+using HSchool.Server.Changelog;
+
+namespace HSchool.Server.Tests;
+
+public class BuildChangelogTests
+{
+    private const string Head = "cccccccccccccccccccccccccccccccccccccccc";
+    private const string Mark = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
+    private const string Merge = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+    private const string Unknown = "dddddddddddddddddddddddddddddddddddddddd";
+
+    private static readonly string Sample = string.Join('\n',
+        Head,
+        $"{Head}\u001f2026-01-03T12:00:00Z\u001fAdd changelog window",
+        $"{Mark}\u001f2026-01-02T12:00:00Z\u001fMark phase 54 in progress.",
+        $"{Merge}\u001f2026-01-01T12:00:00Z\u001fMerge branch 'phase/53-weather-commute'");
+
+    [Fact]
+    public void VisibleSince_KnownSha_ReturnsOlderToNewerWithoutMarkPhase()
+    {
+        var changelog = BuildChangelog.Parse(Sample);
+
+        var visible = changelog.VisibleSince(Merge);
+
+        var commit = Assert.Single(visible);
+        Assert.Equal(Head, commit.Sha);
+        Assert.Equal("Add changelog window", commit.Subject);
+    }
+
+    [Fact]
+    public void VisibleSince_MarkPhaseAnchor_StillReturnsLaterVisibleCommits()
+    {
+        var changelog = BuildChangelog.Parse(Sample);
+
+        var visible = changelog.VisibleSince(Mark);
+
+        var commit = Assert.Single(visible);
+        Assert.Equal("Add changelog window", commit.Subject);
+    }
+
+    [Fact]
+    public void VisibleSince_MissingUnknownOrCurrent_ReturnsEmpty()
+    {
+        var changelog = BuildChangelog.Parse(Sample);
+
+        Assert.Empty(changelog.VisibleSince(null));
+        Assert.Empty(changelog.VisibleSince(""));
+        Assert.Empty(changelog.VisibleSince(Unknown));
+        Assert.Empty(changelog.VisibleSince(Head));
+        Assert.Empty(changelog.VisibleSince(Head.ToUpperInvariant()));
+    }
+
+    [Fact]
+    public void IsMarkPhase_MatchesStatusLineSubjects()
+    {
+        Assert.True(BuildChangelog.IsMarkPhase("Mark phase 54 in progress."));
+        Assert.True(BuildChangelog.IsMarkPhase("Mark phase 47 romance pack as complete."));
+        Assert.False(BuildChangelog.IsMarkPhase("Merge branch 'phase/54-whats-new'"));
+    }
+}