Cannot implicitly convert type void to int

Question

I'm creating a unit test for an existing project.

• n1 and n2 are input numbers
• op is operands in a switch case in the main program

The problem is with actual. I cannot match the expected and actual value because I get the error cannot implicitly convert void to int.

My unit test:

[TestMethod()]
public void docalcTest(int actual)
{
    Form1 target = new Form1(); // TODO: Passenden Wert initialisieren

    double n1 = 15; // TODO: Passenden Wert initialisieren
    double n2 = 3; // TODO: Passenden Wert initialisieren
    int op = 2; // TODO: Passenden Wert initialisieren
    int expected = 5;

    actual = target.docalc(n1, n2, op);

    Assert.AreEqual(expected,actual);
}

The code for docalc:

public void docalc(double n1, double n2, int op)
{
    result = 0;
    setText("clear");

    switch (op)
    {
        case 1:
            result = n1 + n2;
            break;
        case 2:
            result = n1 - n2;
            break;
        case 3:
            result = n1 * n2;
            break;
        case 4:
            result = n1 / n2;
            break;
    }

    setText(result.ToString());
}

Answer 1

Your method target.docalc() is a void method, while actual is an int. You can't assign void to an int, as the compiler says.

According to your comment (you really should just edit your question), your docalc() looks like this:

public void docalc(double n1, double n2, int op) 
{   
    result = 0; 

    ...

    setText(result.ToString());
}

You'll have to change the return type of the method to int, and return result:

public int docalc(double n1, double n2, int op) 
{   
    int result = 0; 

    ...

    return result;
}

Sidenote, why do you do this?

[TestMethod()]
public void docalcTest(int actual)
{
     ...

    actual = ...

The test method will be called without parameters, so it's a bit useless there. You might want to change it to:

[TestMethod()]
public void docalcTest()
{
     ...

    int actual = ...