tests: add tests for anthropic file model

src/AnthropicClient/Models/AnthropicFile.cs

@@ -17,7 +17,7 @@ public class AnthropicFile
   /// Object type.
   /// </summary>
   [JsonPropertyName("type")]
-  public string Type { get; init; } = "file";
+  public string Type { get; init; } = string.Empty;
 
   /// <summary>
   /// Original filename of the uploaded file.

tests/AnthropicClient.Tests/Unit/Models/AnthropicFileTests.cs

@@ -0,0 +1,95 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class AnthropicFileTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""id"": ""file-123"",
+    ""type"": ""file"",
+    ""filename"": ""test.txt"",
+    ""created_at"": ""2023-10-01T00:00:00Z"",
+    ""size_bytes"": 1024,
+    ""mime_type"": ""text/plain"",
+    ""downloadable"": true
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var result = new AnthropicFile();
+
+    result.Id.Should().BeEmpty();
+    result.Type.Should().BeEmpty("file");
+    result.Name.Should().BeEmpty();
+    result.CreatedAt.Should().Be(DateTimeOffset.MinValue);
+    result.Size.Should().Be(0);
+    result.MimeType.Should().BeEmpty();
+    result.Downloadable.Should().BeFalse();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithValues_ItShouldInitializeProperties()
+  {
+    var file = new AnthropicFile
+    {
+      Id = "file-123",
+      Type = "file",
+      Name = "test.txt",
+      CreatedAt = new DateTimeOffset(2023, 10, 1, 0, 0, 0, TimeSpan.Zero),
+      Size = 1024,
+      MimeType = "text/plain",
+      Downloadable = true
+    };
+
+    file.Id.Should().Be("file-123");
+    file.Type.Should().Be("file");
+    file.Name.Should().Be("test.txt");
+    file.CreatedAt.Should().Be(new DateTimeOffset(2023, 10, 1, 0, 0, 0, TimeSpan.Zero));
+    file.Size.Should().Be(1024);
+    file.MimeType.Should().Be("text/plain");
+    file.Downloadable.Should().BeTrue();
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var file = new AnthropicFile
+    {
+      Id = "file-123",
+      Type = "file",
+      Name = "test.txt",
+      CreatedAt = new DateTimeOffset(2023, 10, 1, 0, 0, 0, TimeSpan.Zero),
+      Size = 1024,
+      MimeType = "text/plain",
+      Downloadable = true
+    };
+
+    var json = Serialize(file);
+
+    var expectedJson = @"{
+      ""id"": ""file-123"",
+      ""type"": ""file"",
+      ""filename"": ""test.txt"",
+      ""created_at"": ""2023-10-01T00:00:00+00:00"",
+      ""size_bytes"": 1024,
+      ""mime_type"": ""text/plain"",
+      ""downloadable"": true
+    }";
+
+    JsonAssert.Equal(expectedJson, json, true);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedValues()
+  {
+    var file = Deserialize<AnthropicFile>(_testJson);
+
+    file.Should().NotBeNull();
+    file!.Id.Should().Be("file-123");
+    file.Type.Should().Be("file");
+    file.Name.Should().Be("test.txt");
+    file.CreatedAt.Should().Be(new DateTimeOffset(2023, 10, 1, 0, 0, 0, TimeSpan.Zero));
+    file.Size.Should().Be(1024);
+    file.MimeType.Should().Be("text/plain");
+    file.Downloadable.Should().BeTrue();
+  }
+}