AgentSkillsCN

fluent-assertions

使用 FluentAssertions 库编写流畅、易读的测试断言与验证。 适用于：编写单元测试、验证服务响应、断言领域实体状态、测试集合与异步操作时使用。

SKILL.md
--- frontmatter
name: fluent-assertions
description: |
  Writes fluent, readable test assertions and validations using FluentAssertions library.
  Use when: Writing unit tests, validating service responses, asserting domain entity states, testing collections and async operations.
allowed-tools: Read, Edit, Write, Glob, Grep, Bash

FluentAssertions Skill

FluentAssertions provides a fluent API for expressing test assertions in C#. In VanDaemon, it's used alongside xUnit and Moq for testing services, controllers, plugins, and the JsonFileStore persistence layer. The library produces clear failure messages that explain exactly what went wrong.

Quick Start

Basic Value Assertions

csharp
// From VanDaemon test patterns
result.Should().NotBeNull();
result.Should().Be(expectedValue);
tank.CurrentLevel.Should().BeInRange(0, 100);
tank.IsActive.Should().BeTrue();

Collection Assertions

csharp
// Testing tank service returns
var tanks = await tankService.GetAllTanksAsync();
tanks.Should().NotBeNull();
tanks.Should().HaveCount(3);
tanks.Should().AllSatisfy(t => t.IsActive.Should().BeTrue());
tanks.Should().Contain(t => t.Type == TankType.FreshWater);

Async Operation Assertions

csharp
// Testing async service methods
await service.Invoking(s => s.GetTankByIdAsync(Guid.Empty))
    .Should().ThrowAsync<ArgumentException>();

var result = await service.GetAllControlsAsync();
result.Should().BeEquivalentTo(expectedControls);

Key Concepts

ConceptUsageExample
Should()Entry point for all assertionsvalue.Should().Be(5)
BeEquivalentTo()Deep object comparisonactual.Should().BeEquivalentTo(expected)
AllSatisfy()Assert condition on all itemslist.Should().AllSatisfy(x => x.IsActive.Should().BeTrue())
Invoking()Test exception throwingobj.Invoking(x => x.Method()).Should().Throw<T>()
Because()Custom failure messagevalue.Should().Be(5, "configuration requires this")

Common Patterns

Service Response Validation

When: Testing application services like TankService, ControlService

csharp
var mockFileStore = new Mock<IJsonFileStore>();
mockFileStore.Setup(x => x.LoadAsync<List<Tank>>("tanks.json", It.IsAny<CancellationToken>()))
    .ReturnsAsync(testTanks);

var service = new TankService(logger, mockFileStore.Object);
var result = await service.GetAllTanksAsync();

result.Should().NotBeNull();
result.Should().HaveCount(2);
result.First().Name.Should().Be("Fresh Water");

Entity State Assertions

When: Validating domain entity properties

csharp
var tank = new Tank { Type = TankType.FreshWater, AlertLevel = 10 };
tank.Type.Should().Be(TankType.FreshWater);
tank.AlertLevel.Should().BeGreaterThanOrEqualTo(0);
tank.AlertWhenOver.Should().BeFalse("fresh water alerts when level drops below threshold");

See Also

  • •patterns - Assertion patterns by type
  • •workflows - Testing workflows and best practices

Related Skills

  • •xunit skill for test framework fundamentals
  • •moq skill for mocking dependencies before asserting results
  • •csharp skill for language features used in assertions