什么是Fluent Assertions

Fluent Assertions 是 .NET 平台下的一组扩展方法，用于单元测试中的断言。它使你的单元测试中的断言看起来更自然流畅。断言风格如下：

string actual = "ABCDEFGHI";
actual.Should().StartWith("AB").And.EndWith("HI").And.Contain("EF").And.HaveLength(9);

更多内容可查看 Fluent Assertions Documentation

待测试API

[HttpGet("{id}")]
public async Task<IActionResult> Get(int id)
{
    var sampleData = await _sqliteDbContext.SampleEntity
        .SingleOrDefaultAsync(s => s.Id == id);

    if (sampleData?.StringValue == "ping")
    {
        var pingOk = _foo.Ping("localhost");
        if (!pingOk)
            return NotFound();
    }

    return Ok(sampleData);
}

测试用例

Install-Package FluentAssertions -Version 5.10.2
我们对前文中的测试用例进行修改，改动如下：

// Assert
var result = response.Should().BeOfType<OkObjectResult>().Subject;
var sampleData = result.Value.Should().BeAssignableTo<SampleEntity>().Subject;
sampleData.Id.Should().Be(2);
sampleData.BoolValue.Should().BeFalse();
sampleData.StringValue.Should().Be("ping");

完整代码如下

[TestMethod]
public async Task Get_ReturnOK_WithPingTrue_UsingFluentAssertions()
{
    // Arrange
    var dbContext = await GetSqliteDbContextAsync();

    var loggerMock = new Mock<ILogger<SampleController>>();
    var logger = loggerMock.Object;

    var fooMock = new Mock<IFoo>();
    fooMock.Setup(foo => foo.Ping("localhost")).Returns(true);
    var foo = fooMock.Object;

    var controller = new SampleController(dbContext, logger, foo);

    // Act
    var response = await controller.Get(2);

    // Assert
    var result = response.Should().BeOfType<OkObjectResult>().Subject;
    var sampleData = result.Value.Should().BeAssignableTo<SampleEntity>().Subject;
    sampleData.Id.Should().Be(2);
    sampleData.BoolValue.Should().BeFalse();
    sampleData.StringValue.Should().Be("ping");
}

测试通过