Check that number of received calls is within range with NSubstitute

Question

Is there a way to check with NSubstitute that number of received calls falls within certain range?

I would like to do something like:

myMock.Received(r => r > 1 && r <= 5).MyMethod();

Alternatively, if I could get the exact number of received calls that would do the job as well. I am unit testing retries and timeouts and based on system load and other tests running number of retries can vary during unit test execution.

Answer 1

The NSubstitute API does not currently support this exactly (but it's a nice idea!).

There is a hacky-ish way of doing it using the unofficial .ReceivedCalls extension:

var calls = myMock.ReceivedCalls()
    .Count(x => x.GetMethodInfo().Name == nameof(myMock.MyMethod));
Assert.InRange(calls, 1, 5);

The better way to do this using a custom Quantity from the NSubstitute.ReceivedExtensions namespace:

// DISCLAIMER: draft code only. Review and test before using.
public class RangeQuantity : Quantity {
    private readonly int min;
    private readonly int maxInclusive;
    public RangeQuantity(int min, int maxInclusive) {
        // TODO: validate args, min < maxInclusive.
        this.min = min;
        this.maxInclusive = maxInclusive;
    }
    public override string Describe(string singularNoun, string pluralNoun) => 
        $"between {min} and {maxInclusive} (inclusive) {((maxInclusive == 1) ? singularNoun : pluralNoun)}";

    public override bool Matches<T>(IEnumerable<T> items) {
        var count = items.Count();
        return count >= min && count <= maxInclusive;
    }

    public override bool RequiresMoreThan<T>(IEnumerable<T> items) => items.Count() < min;
}

Then:

myMock.Received(new RangeQuantity(3,5)).MyMethod();

(Note you will need using NSubstitute.ReceivedExtensions; for this.)