How can I simulate an exception being thrown in C# unit tests?
I want to be able to have 100% coverage of my code, but I can\'t test the code with exceptions that may oc
What you need is stub - an object that will simulate certain conditions for your code. For testing purposes, you usually replace real object implementation with stub (or other type of faked object). In your case, consider:
public class MyClass
{
private IDataProvider dataProvider;
public void MyMethod()
{
try
{
this.dataProvider.GetData();
}
catch (OutOfMemoryException)
{
}
}
}
Now, class you are testing should be configurable at some level - so that you can easily replace real DataProvider
implementation with stubbed/faked one when testing (like you said, you don't want to destroy your DB - nobody wants!). This can be achieved for example by constructor injection (or in fact, any other dependency injection technique).
Your test then is trivial (some made-up requirement to test when exception is thrown):
[Test]
public void MyMethod_DataProviderThrowsOutOfMemoryException_LogsError()
{
var dataProviderMock = new Mock();
dataProviderMock
.Setup(dp => dp.GetData())
.Throws();
var myClass = new MyClass(dataProviderMock);
myClass.MyMethod();
// assert whatever needs to be checked
}