- Getting started
- Creating a substitute
- Setting a return value
- Return for specific args
- Return for any args
- Return from a function
- Multiple return values
- Replacing return values
- Checking received calls
- Clearing received calls
- Argument matchers
- Callbacks, void calls and When..Do
- Throwing exceptions
- Safe configuration and overlapping calls
- Raising events
- Auto and recursive mocks
- Setting out and ref args
- Actions with argument matchers
- Checking call order
- Partial subs and test spies
- Return for all calls of a type
- Threading
- Compatibility argument matchers
- NSubstitute.Analyzers
Setting out and ref args
Out and ref arguments can be set using a Returns() callback, or using When..Do.
public interface ILookup {
bool TryLookup(string key, out string value);
}
For the interface above we can configure the return value and set the output of the second argument like this:
//Arrange
var lookup = Substitute.For<ILookup>();
lookup
.TryLookup("hello", out Arg.Is(""))
.Returns(x => {
x[1] = "world!";
return true;
});
//Act
var value = "";
var result = lookup.TryLookup("hello", out value);
//Assert
Assert.True(result);
Assert.AreEqual(value, "world!");
Matching after assignments
Be careful when using an argument matcher with a reference we also assign to. The assignment can cause previously matching arguments to stop matching.
var counter = 0;
var value = "";
var lookup = Substitute.For<ILookup>();
lookup
.TryLookup("hello", out Arg.Is(value)) // value is "", matcher will check for ""
.Returns(x => {
x[1] = "assigned"; // Assign to 2nd arg
counter++; // Count this matching call
return true;
});
// value is "", this will match!
lookup.TryLookup("hello", out value);
// Call matches, counter is now 1:
Assert.AreEqual(1, counter);
// value is now "assigned" but arg matcher is still looking for "", will NOT match anymore!
lookup.TryLookup("hello", out value);
// Call does NOT match anymore, counter is still 1:
Assert.AreEqual(1, counter);