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Chris0JekyChris0Jeky
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Merge pull request #601 from Chris0Jeky/test/89-property-based-fuzz-testing
Add property-based and fuzz testing pilot for domain/API contracts
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‎backend/tests/Taskdeck.Application.Tests/Fuzz/ExportImportContractFuzzTests.cs‎

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using System.Text.Json;
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using FluentAssertions;
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using FsCheck;
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using FsCheck.Xunit;
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using Taskdeck.Application.DTOs;
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namespace Taskdeck.Application.Tests.Fuzz;
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/// <summary>
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/// Fuzz-style tests for export/import DTO serialization contracts.
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/// Verifies JSON roundtrip fidelity and that deserialization of arbitrary payloads
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/// never throws unhandled exceptions.
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/// Replay: set Replay = "seed,size" on any [Property] to reproduce a failing case.
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/// </summary>
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public class ExportImportContractFuzzTests
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{
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private const int MaxTests = 200;
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private static readonly JsonSerializerOptions CamelCaseOptions = new()
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{
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PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
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PropertyNameCaseInsensitive = true
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};
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[Property(MaxTest = MaxTests)]
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public Property ImportBoardDto_Roundtrip_PreservesData()
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{
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return Prop.ForAll(
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ValidImportBoardDtoArb(),
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dto =>
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{
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var json = JsonSerializer.Serialize(dto, CamelCaseOptions);
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var deserialized = JsonSerializer.Deserialize<ImportBoardDto>(json, CamelCaseOptions);
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deserialized.Should().NotBeNull();
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deserialized!.Name.Should().Be(dto.Name);
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deserialized.Description.Should().Be(dto.Description);
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deserialized.Columns.Count().Should().Be(dto.Columns.Count());
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deserialized.Cards.Count().Should().Be(dto.Cards.Count());
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deserialized.Labels.Count().Should().Be(dto.Labels.Count());
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});
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}
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[Property(MaxTest = MaxTests)]
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public Property ImportBoardDto_Deserialize_NeverThrows_OnArbitraryJson()
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{
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return Prop.ForAll(
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Arb.From<string>(),
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json =>
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{
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// Deserialization of arbitrary strings should either succeed or throw JsonException,
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// never an unhandled exception type
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try
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{
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JsonSerializer.Deserialize<ImportBoardDto>(json ?? "null", CamelCaseOptions);
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}
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catch (JsonException)
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{
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// Expected for malformed JSON
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}
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catch (Exception ex)
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{
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// Any other exception type is a test failure
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ex.Should().BeNull($"Unexpected exception type {ex.GetType()}: {ex.Message}");
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}
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});
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}
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[Property(MaxTest = MaxTests)]
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public Property ImportColumnDto_Roundtrip_PreservesData()
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{
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return Prop.ForAll(
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ValidImportColumnDtoArb(),
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dto =>
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{
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var json = JsonSerializer.Serialize(dto, CamelCaseOptions);
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var deserialized = JsonSerializer.Deserialize<ImportColumnDto>(json, CamelCaseOptions);
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deserialized.Should().NotBeNull();
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deserialized!.Name.Should().Be(dto.Name);
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deserialized.Position.Should().Be(dto.Position);
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deserialized.WipLimit.Should().Be(dto.WipLimit);
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});
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}
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[Property(MaxTest = MaxTests)]
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public Property ImportCardDto_Roundtrip_PreservesData()
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{
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return Prop.ForAll(
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ValidImportCardDtoArb(),
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dto =>
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{
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var json = JsonSerializer.Serialize(dto, CamelCaseOptions);
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var deserialized = JsonSerializer.Deserialize<ImportCardDto>(json, CamelCaseOptions);
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deserialized.Should().NotBeNull();
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deserialized!.Title.Should().Be(dto.Title);
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deserialized.Description.Should().Be(dto.Description);
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deserialized.ColumnName.Should().Be(dto.ColumnName);
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deserialized.Position.Should().Be(dto.Position);
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});
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}
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[Property(MaxTest = MaxTests)]
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public Property ImportLabelDto_Roundtrip_PreservesData()
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{
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return Prop.ForAll(
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ValidImportLabelDtoArb(),
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dto =>
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{
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var json = JsonSerializer.Serialize(dto, CamelCaseOptions);
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var deserialized = JsonSerializer.Deserialize<ImportLabelDto>(json, CamelCaseOptions);
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deserialized.Should().NotBeNull();
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deserialized!.Name.Should().Be(dto.Name);
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deserialized.Color.Should().Be(dto.Color);
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});
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}
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[Property(MaxTest = MaxTests)]
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public Property ImportBoardDto_ExtraFields_IgnoredGracefully()
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{
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// Verify that extra/unknown fields in JSON don't break deserialization
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return Prop.ForAll(
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Arb.From(Gen.OneOf(
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Gen.Constant("{\"name\":\"Test\",\"unknownField\":42,\"columns\":[],\"cards\":[],\"labels\":[]}"),
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Gen.Constant("{\"name\":\"Test\",\"description\":\"Desc\",\"extra\":{\"nested\":true},\"columns\":[],\"cards\":[],\"labels\":[]}"),
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Gen.Constant("{\"name\":\"Test\",\"columns\":[{\"name\":\"Col\",\"position\":0,\"extra\":true}],\"cards\":[],\"labels\":[]}")
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)),
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json =>
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{
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var act = () => JsonSerializer.Deserialize<ImportBoardDto>(json, CamelCaseOptions);
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act.Should().NotThrow("extra fields should be silently ignored");
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});
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}
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[Property(MaxTest = MaxTests)]
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public Property ImportBoardDto_MissingFields_HandledGracefully()
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{
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return Prop.ForAll(
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Arb.From(Gen.OneOf(
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Gen.Constant("{}"),
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Gen.Constant("{\"name\":null}"),
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Gen.Constant("{\"name\":\"Test\"}"),
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Gen.Constant("{\"columns\":[]}"),
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Gen.Constant("{\"name\":\"\",\"columns\":null,\"cards\":null,\"labels\":null}")
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)),
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json =>
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{
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// Should deserialize without throwing (fields may be null/default)
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var act = () => JsonSerializer.Deserialize<ImportBoardDto>(json, CamelCaseOptions);
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act.Should().NotThrow("missing fields should result in defaults, not exceptions");
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});
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}
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[Property(MaxTest = MaxTests)]
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public Property StarterPackManifestDto_Roundtrip_PreservesData()
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{
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return Prop.ForAll(
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ValidStarterPackDtoArb(),
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dto =>
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{
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var json = JsonSerializer.Serialize(dto, CamelCaseOptions);
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var deserialized = JsonSerializer.Deserialize<StarterPackManifestDto>(json, CamelCaseOptions);
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deserialized.Should().NotBeNull();
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deserialized!.SchemaVersion.Should().Be(dto.SchemaVersion);
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deserialized.PackId.Should().Be(dto.PackId);
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deserialized.DisplayName.Should().Be(dto.DisplayName);
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deserialized.Labels.Count.Should().Be(dto.Labels.Count);
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deserialized.Columns.Count.Should().Be(dto.Columns.Count);
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});
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}
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private static Arbitrary<ImportBoardDto> ValidImportBoardDtoArb()
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{
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var gen = Gen.Choose(0, 5).SelectMany(colCount =>
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Gen.Choose(0, 5).SelectMany(cardCount =>
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Gen.Choose(0, 3).Select(labelCount =>
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{
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var columns = Enumerable.Range(0, colCount)
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.Select(i => new ImportColumnDto($"Column{i}", i, i > 0 ? i * 3 : (int?)null))
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.ToList();
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var columnNames = columns.Select(c => c.Name).ToArray();
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var cards = Enumerable.Range(0, cardCount)
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.Select(i => new ImportCardDto(
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$"Card{i}",
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$"Description for card {i}",
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columnNames.Length > 0 ? columnNames[i % columnNames.Length] : "Default",
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i,
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i % 2 == 0 ? DateTimeOffset.UtcNow.AddDays(i) : null,
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null))
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.ToList();
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var labels = Enumerable.Range(0, labelCount)
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.Select(i =>
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{
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var hex = ((i + 1) * 55 % 256).ToString("X2");
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return new ImportLabelDto($"Label{i}", $"#{hex}{hex}{hex}");
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})
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.ToList();
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return new ImportBoardDto(
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$"Board-{colCount}-{cardCount}",
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"Test board description",
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columns,
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cards,
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labels);
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})));
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return Arb.From(gen);
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}
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private static Arbitrary<ImportColumnDto> ValidImportColumnDtoArb()
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{
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var gen = Gen.Choose(0, 100).SelectMany(pos =>
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Gen.OneOf(
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Gen.Constant((int?)null),
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Gen.Choose(1, 50).Select(v => (int?)v)
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).Select(wipLimit =>
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new ImportColumnDto($"Column-{pos}", pos, wipLimit)));
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return Arb.From(gen);
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}
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private static Arbitrary<ImportCardDto> ValidImportCardDtoArb()
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{
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var gen = Gen.Choose(0, 100).Select(pos =>
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new ImportCardDto(
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$"Card-{pos}",
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$"Description for card {pos}",
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"Default",
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pos,
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pos % 2 == 0 ? DateTimeOffset.UtcNow.AddDays(pos) : null,
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pos % 3 == 0 ? new[] { "Label1" } : null));
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return Arb.From(gen);
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}
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private static Arbitrary<ImportLabelDto> ValidImportLabelDtoArb()
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{
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var gen = Gen.Choose(0, 255).Select(i =>
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{
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var hex = i.ToString("X2");
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return new ImportLabelDto($"Label-{i}", $"#{hex}{hex}{hex}");
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});
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return Arb.From(gen);
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}
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private static Arbitrary<StarterPackManifestDto> ValidStarterPackDtoArb()
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{
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var gen = Gen.Choose(1, 3).SelectMany(labelCount =>
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Gen.Choose(1, 4).Select(colCount =>
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{
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var labels = Enumerable.Range(0, labelCount)
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.Select(i =>
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{
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var hex = ((i + 1) * 37 % 256).ToString("X2");
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return new StarterPackLabelDto
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{
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Name = $"Label{i}",
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Color = $"#{hex}{hex}{hex}"
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};
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})
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.ToList();
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var columns = Enumerable.Range(0, colCount)
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.Select(i => new StarterPackColumnDto
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{
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Name = $"Column{i}",
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Position = i,
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WipLimit = i > 0 ? i * 5 : null
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})
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.ToList();
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return new StarterPackManifestDto
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{
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SchemaVersion = "1.0",
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PackId = "test-pack",
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DisplayName = "Test Pack",
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Description = "Fuzz test pack",
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Compatibility = new StarterPackCompatibilityDto
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{
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MinTaskdeckVersion = "0.1.0",
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RequiredFeatures = new List<string>()
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},
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Tags = new List<string> { "test" },
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Labels = labels,
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Columns = columns,
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Templates = new List<StarterPackCardTemplateDto>(),
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SeedCards = new List<StarterPackSeedCardDto>()
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};
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}));
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return Arb.From(gen);
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}
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}

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