NSubstitute、out 参数和条件返回

Question

我有一个与下面我想在 NSubstitute 中模拟的场景没有什么不同...

public interface IGrabSomeData
{
    bool GrabThatData(string filename, out byte[] data);
}

...使用此接口，我希望它采用文件名并检索字节数据。使用 NSubstitute 我想向它传递特定的文件名并返回不同的或空的字节数组。通常，我会通过在我的脚手架中指定参数并酌情使用“返回”元素来执行此操作。不幸的是，我不能使用 'Arg.Any()' 参数，因为它提供了......

ref 或 out 参数必须是可赋值变量

...但如果我这样做，它始终是一个空字节数组。这是使用上述接口的快速演示...

IGrabSomeData grabSomeData_1 = Substitute.For<IGrabSomeData>();
IGrabSomeData grabSomeData_2 = Substitute.For<IGrabSomeData>();

// Doesn't work
byte[] empty = { };
grabSomeData_1.GrabThatData(Arg.Any<string>(), out empty).Returns(x => { x[1] = new byte[] { 0, 1, 2 }; return true; });
byte[] test1 = {};
var result1 = grabSomeData_1.GrabThatData("" , out test1);
Assert.IsTrue( test1.length > 0); // FAILS

// Does work
grabSomeData_2.GrabThatData(Arg.Any<string>(), out empty).ReturnsForAnyArgs(x => { x[1] = new byte[] { 0, 1, 2 }; return true; });
byte[] test2 = { };
var result2 = grabSomeData_2.GrabThatData("", out test2);   
Assert.IsTrue(empty.Length > 0); // Success!

简而言之，我需要声明“out”参数，但我必须为我的模拟调用分配一个变量——这在特定的“Returns”语句中无法识别。是否有可能实现类似...

IGrabSomeData grabSomeData_1 = Substitute.For<IGrabSomeData>();

byte[] empty = { };
grabSomeData_1.GrabThatData("test1.xml", out empty).Returns(x => { x[1] = new byte[] { 0, 1, 2 }; return true; });
grabSomeData_1.GrabThatData("test2.xml", out empty).Returns(x => { x[1] = new byte[] { 0, 1, 2, 3, 4 }; return true; });
grabSomeData_1.GrabThatData("test3.xml", out empty).Returns(x => { x[1] = new byte[] { 0, 1 }; return true; });

byte[] test1 = {};
var result1 = grabSomeData_1.GrabThatData("test1.xml", out test1);
Assert.IsTrue(test1.Length == 2);

// etc.

提前致谢。

Answer 1

这未经测试，但也许您可以使用“Arg.Is”，如下例所示：

IGrabSomeData grabSomeData_1 = Substitute.For<IGrabSomeData>();

byte[] empty = { };
grabSomeData_1.GrabThatData(Arg.Is<string>(x => string.Equals(x, "test1.xml")), out empty).Returns(x => { x[1] = new byte[] { 0, 1, 2 }; return true; });
grabSomeData_1.GrabThatData(Arg.Is<string>(x => string.Equals(x, "test2.xml")), out empty).Returns(x => { x[1] = new byte[] { 0, 1, 2, 3, 4 }; return true; });
grabSomeData_1.GrabThatData(Arg.Is<string>(x => string.Equals(x, "test3.xml")), out empty).Returns(x => { x[1] = new byte[] { 0, 1 }; return true; });

byte[] test1 = {};
var result1 = grabSomeData_1.GrabThatData("test1.xml", out test1);
Assert.IsTrue(test1.Length == 2);