Question

I try to make my simple mock to work, but it’s too tedious.
I get one mistake in this place

(string s1, string s2) => { return (string)(s1 + s2); });

The message says that

“Delegate ‘System.Func’ does not take 2 arguments”

but in this article all works

all my code here.

public interface IWriteTwoString
{
    string WriteTwoStrings(string s1, string s2);
}

public MyPriceReducerTest()
{
    Mock<IWriteTwoString> writeMock = new Mock<IWriteTwoString>(MockBehavior.Strict);
    writeMock.Setup(m => m.WriteTwoStrings(It.IsAny<string>(), It.IsAny<string>()))
       .Returns<string>((string s1, string s2) => { return (string)(s1 + s2); });
}

Answer 1

Your problem is with the expression: Returns<string> which tells moq that your WriteTwoStrings has one string parameter, but you have two therefore you get an error.

So you need to write:

.Returns<string, string>((string s1, string s2) => { return (string)(s1 + s2); });

Or you can leave out the types completely because the compiler can infer them:

.Returns((string s1, string s2) => { return (string)(s1 + s2); });