Return for all calls of a type

We can return a specific value for all calls to a substitute using sub.ReturnsForAll<T>(T value). This will cause sub to return value for all calls that return something of type T and are not already stubbed.

Note: we need using NSubstitute.Extensions to import the .ReturnsForAll<T>() extension method.

The type must match exactly: .ReturnsForAll<Cat>(cat) will not set a return value for a call that returns Animal, even if Cat inherits from Animal. To return for the super-type, use .ReturnsForAll<Animal>(cat). (If you’d like a change in this behaviour, please let us know).

There is also an overload that takes a Func<CallInfo,T> so the value to return will be calculated each time.

Fluent interface example

One example of where this can be useful is a builder-style interface where each call returns a reference to itself.

// using NSubstitute.Extensions;

public interface IWidgetBuilder {
  IWidgetBuilder Quantity(int i); 
  IWidgetBuilder AddLineItem(string s); 
  IWidgetContainer GetWidgets();

public class ProductionLine {
  IWidgetBuilder builder;
  public ProductionLine(IWidgetBuilder builder) {
    this.builder = builder;

  public IWidgetContainer Run() {
    return builder
              .AddLineItem("Other thingoe")

public void ShouldReturnWidgetsFromBuilder() {
  var builder = Substitute.For<IWidgetBuilder>();
  var line = new ProductionLine(builder);

  var result = line.Run();

  Assert.That(result, Is.EqualTo(builder.GetWidgets()));

In this test builder will return a reference to itself whenever a call returns a value of type IWidgetBuilder, so the chained calls will all work on the same builder instance.

Returns vs. ReturnsForAll

Calls will only use .ReturnsForAll values when NSubstitute can’t find an explicitly stubbed value for the call. So if we set sub.GetWidget().Returns(widget), that will take precendence over any values stubbed by sub.ReturnsForAll<Widget>(otherWidget).

public void ReturnsTakesPrecedence() {
  var widget = new Widget();
  var otherWidget = new Widget();
  var sub = Substitute.For<IWidgetExample>();

  Assert.That(sub.GetWidget(1), Is.SameAs(widget));
  Assert.That(sub.GetWidget(42), Is.SameAs(otherWidget));