code REORG, pour partage pkg version entre app et tests

src/PostIt/PostIt.Tests/BlogPostAuthorDtoTests.cs

@@ -0,0 +1,169 @@
+using System.Text.Json;
+using Yavsc.Blogspot;
+
+namespace PostIt.Tests;
+
+/// <summary>
+/// Round-trip tests for the wire shape of a blog post as
+/// serialised by Yavsc.Blogs and consumed by PostIt.
+///
+/// <para>
+/// Background: in 1.0.7, <c>BlogPostDto.Author</c> was typed as
+/// the abstract interface <c>IApplicationUser</c>. System.Text.Json
+/// cannot materialise an interface without a polymorphic
+/// converter, so the "load posts" call from PostIt crashed when
+/// the server returned a post with a populated <c>Author</c>
+/// object. The fix replaced <c>IApplicationUser</c> with a thin
+/// concrete DTO, <c>BlogPostAuthorDto</c>, embedded directly in
+/// <c>BlogPostDto.Author</c>.
+/// </para>
+///
+/// <para>
+/// These tests pin the wire shape: a JSON document with an
+/// <c>Author</c> object must deserialise without throwing and
+/// must round-trip the three fields PostIt exposes in the UI
+/// (Id, UserName, Avatar). They are intentionally placed in
+/// <c>PostIt.Tests</c> — the client-side assembly — so the
+/// regression is caught at the deserialisation boundary, where
+/// it actually manifested in production.
+/// </para>
+/// </summary>
+public class BlogPostAuthorDtoTests
+{
+    private static readonly JsonSerializerOptions CaseInsensitiveJson
+        = new() { PropertyNameCaseInsensitive = true };
+
+    [Fact]
+    public void BlogPostDto_deserialises_with_populated_author()
+    {
+        // A representative JSON shape the server would emit for
+        // GET /api/BlogApi. The Author object is fully populated
+        // — that's the shape that used to break deserialisation
+        // when Author was typed as the abstract IApplicationUser
+        // interface.
+        var json = """
+        {
+          "id": 42,
+          "title": "Premier billet",
+          "article": "Contenu",
+          "photo": null,
+          "dateCreated": "2026-08-01T12:00:00Z",
+          "dateModified": "2026-08-02T12:00:00Z",
+          "userCreated": "alice",
+          "userModified": "alice",
+          "authorId": "u-alice",
+          "isPublished": true,
+          "author": {
+            "id": "u-alice",
+            "userName": "alice",
+            "avatar": "/avatars/alice.png"
+          }
+        }
+        """;
+
+        var post = JsonSerializer.Deserialize<BlogPostDto>(json, CaseInsensitiveJson);
+
+        Assert.NotNull(post);
+        Assert.Equal(42, post!.Id);
+        Assert.Equal("Premier billet", post.Title);
+        Assert.Equal("u-alice", post.AuthorId);
+        Assert.True(post.IsPublished);
+
+        // The actual regression coverage: Author must
+        // materialise as a concrete DTO, not be left null because
+        // of a JsonException on IApplicationUser.
+        Assert.NotNull(post.Author);
+        Assert.Equal("u-alice", post.Author!.Id);
+        Assert.Equal("alice", post.Author.UserName);
+        Assert.Equal("/avatars/alice.png", post.Author.Avatar);
+    }
+
+    [Fact]
+    public void BlogPostDto_deserialises_when_author_is_null()
+    {
+        // The server is allowed to omit Author (the field is
+        // nullable on the wire — it maps to a navigation
+        // property that may not have been Included). The client
+        // must accept that shape without throwing.
+        var json = """
+        {
+          "id": 7,
+          "title": "Sans auteur",
+          "article": null,
+          "photo": null,
+          "dateCreated": "2026-08-01T12:00:00Z",
+          "dateModified": "2026-08-01T12:00:00Z",
+          "userCreated": "system",
+          "userModified": "system",
+          "authorId": "system",
+          "isPublished": false,
+          "author": null
+        }
+        """;
+
+        var post = JsonSerializer.Deserialize<BlogPostDto>(json, CaseInsensitiveJson);
+
+        Assert.NotNull(post);
+        Assert.Null(post!.Author);
+        Assert.Equal("system", post.AuthorId);
+    }
+
+    [Fact]
+    public void BlogPostDto_deserialises_when_author_field_is_missing()
+    {
+        // Forward-compatibility: an older server that doesn't
+        // emit the Author field at all. Should not throw.
+        var json = """
+        {
+          "id": 9,
+          "title": "Ancien format",
+          "article": "Pas d'auteur dans la charge utile",
+          "photo": null,
+          "dateCreated": "2026-07-01T12:00:00Z",
+          "dateModified": "2026-07-01T12:00:00Z",
+          "userCreated": "bob",
+          "userModified": "bob",
+          "authorId": "u-bob",
+          "isPublished": true
+        }
+        """;
+
+        var post = JsonSerializer.Deserialize<BlogPostDto>(json, CaseInsensitiveJson);
+
+        Assert.NotNull(post);
+        Assert.Null(post!.Author);
+    }
+
+    [Fact]
+    public void BlogPostAuthorDto_serialises_back_to_expected_json_shape()
+    {
+        // Pin the wire shape on the way out too. The server
+        // builds BlogPostAuthorDto from an ApplicationUser and
+        // PostIt receives it as JSON; if the field names
+        // change (e.g. case) the round-trip on the client side
+        // is what would silently break.
+        //
+        // The server emits camelCase (ASP.NET Core's Web
+        // defaults — PropertyNamingPolicy = CamelCase). We
+        // mirror that here so the test reflects what the wire
+        // actually looks like. PropertyNameCaseInsensitive on
+        // the client deserialiser means we don't have to
+        // hardcode the casing for the inbound assertions.
+        var author = new BlogPostAuthorDto
+        {
+            Id = "u-alice",
+            UserName = "alice",
+            Avatar = "/avatars/alice.png"
+        };
+
+        var json = JsonSerializer.Serialize(author,
+            new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase });
+
+        using var doc = JsonDocument.Parse(json);
+        var root = doc.RootElement;
+
+        Assert.True(root.TryGetProperty("id", out _));
+        Assert.True(root.TryGetProperty("userName", out _));
+        Assert.True(root.TryGetProperty("avatar", out _));
+    }
+}