Full Comparison: KnockOff vs Moq vs NSubstitute

Side-by-side comparisons for methods, properties, events, delegates, and indexers.

For argument matching, argument capture, and method overload resolution comparisons, see the README.

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Methods

Task	Moq	NSubstitute	KnockOff
Return value	mock.Setup(x => x.Add(1, 2)).Returns(3);	calc.Add(1, 2).Returns(3);	stub.Add.Return(3);
Any argument	mock.Setup(x => x.Add(It.IsAny<int>(), It.IsAny<int>())).Returns(10);	calc.Add(Arg.Any<int>(), Arg.Any<int>()).Returns(10);	stub.Add.Return(10);
Match values	mock.Setup(x => x.Add(1, 2)).Returns(100);	calc.Add(1, 2).Returns(100);	stub.Add.When((1, 2)).Return(100);
Conditional	mock.Setup(x => x.Add(It.IsAny<int>(), It.IsAny<int>())).Returns<int, int>((a, b) => a > 0 ? a + b : 0);	calc.Add(Arg.Any<int>(), Arg.Any<int>()).Returns(x => ...);	stub.Add.Return((a, b) => a > 0 ? a + b : 0);
Throw	mock.Setup(x => x.Add(It.IsAny<int>(), It.IsAny<int>())).Throws<Exception>();	calc.Add(Arg.Any<int>(), Arg.Any<int>()).Throws<Exception>();	stub.Add.Return((a, b) => throw new Exception());
Callback	mock.Setup(x => x.Add(It.IsAny<int>(), It.IsAny<int>())).Returns(3).Callback<int, int>((a, b) => log.Add(a));	calc.Add(Arg.Any<int>(), Arg.Any<int>()).Returns(3).AndDoes(x => ...);	stub.Add.Return((a, b) => { log.Add(a); return 3; });
Sequence	mock.SetupSequence(x => x.Add(1, 2)).Returns(1).Returns(2).Returns(3);	calc.Add(1, 2).Returns(1, 2, 3);	stub.Add.Return(1, 2, 3);
Async	mock.Setup(x => x.GetUserAsync(1)).ReturnsAsync(user);	repo.GetUserAsync(1).Returns(user);	stub.GetUserAsync.Return(user);
Verify called	mock.Verify(x => x.Add(1, 2));	calc.Received().Add(1, 2);	stub.Add.Verify();
Verify count	mock.Verify(x => x.Add(It.IsAny<int>(), It.IsAny<int>()), Times.Exactly(3));	calc.Received(3).Add(Arg.Any<int>(), Arg.Any<int>());	stub.Add.Verify(Called.Exactly(3));

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Properties

Task	Moq	NSubstitute	KnockOff
Setup getter	mock.Setup(x => x.Mode).Returns("Scientific");	calc.Mode.Returns("Scientific");	stub.Mode.Get("Scientific");
Setup setter	mock.SetupSet(x => x.Mode = It.IsAny<string>()).Callback<string>(v => captured = v);	calc.When(x => x.Mode = Arg.Any<string>()).Do(x => ...);	stub.Mode.Set((v) => captured = v);
Verify getter	mock.VerifyGet(x => x.Mode);	_ = calc.Received().Mode;	stub.Mode.VerifyGet();
Verify setter	mock.VerifySet(x => x.Mode = "Scientific");	calc.Received().Mode = "Scientific";	stub.Mode.VerifySet();
Verify count	mock.VerifyGet(x => x.Mode, Times.Exactly(3));	_ = calc.Received(3).Mode;	stub.Mode.VerifyGet(Called.Exactly(3));
Capture value	mock.SetupSet(x => x.Mode = It.IsAny<string>()).Callback<string>(v => captured = v);	calc.When(x => x.Mode = Arg.Do<string>(v => ...)).Do(...);	stub.Mode.LastSetValue (built-in)

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Events

Task	Moq	NSubstitute	KnockOff
Raise event	mock.Raise(x => x.PoweringUp += null, EventArgs.Empty);	calc.PoweringUp += Raise.Event();	stub.PoweringUp.Raise(stub, EventArgs.Empty);
Raise with args	mock.Raise(x => x.PoweringUp += null, sender, args);	calc.PoweringUp += Raise.EventWith(sender, args);	stub.PoweringUp.Raise(sender, args);
Verify subscription	(not available)	(not available)	stub.PoweringUp.VerifyAdd(Called.Once);
Verify unsubscription	(not available)	(not available)	stub.PoweringUp.VerifyRemove(Called.Once);
Check subscribers	(not available)	(not available)	stub.PoweringUp.HasSubscribers

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Delegates

Task	Moq	NSubstitute	KnockOff
Setup	mock.Setup(x => x(It.IsAny<int>())).Returns("result");	factory(Arg.Any<int>()).Returns("result");	stub.Interceptor.Return("result");
With logic	mock.Setup(x => x(It.Is<int>(v => v > 0))).Returns<int>(x => $"val: {x}");	factory(Arg.Is<int>(x => x > 0)).Returns(x => $"val: {x.Arg<int>()}");	stub.Interceptor.Return((x) => $"val: {x}");
Sequence	mock.SetupSequence(x => x(It.IsAny<int>())).Returns(1).Returns(2).Returns(3);	factory(Arg.Any<int>()).Returns(1, 2, 3);	stub.Interceptor.Return(1, 2, 3);
Async	mock.Setup(x => x(1)).ReturnsAsync(42);	asyncOp(1).Returns(42);	stub.Interceptor.Return(42); (auto-wraps)
Match values	mock.Setup(x => x(42)).Returns("found");	(per-parameter Arg.Is)	stub.Interceptor.When(42).Return("found");
Verify	mock.Verify(x => x(42));	factory.Received()(42);	stub.Interceptor.Verify();
Verify count	mock.Verify(x => x(It.IsAny<int>()), Times.Exactly(3));	factory.Received(3)(Arg.Any<int>());	stub.Interceptor.Verify(Called.Exactly(3));
Capture	(manual with Callback)	(manual with Arg.Do)	stub.Interceptor.LastArg (built-in)

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Indexers

Task	Moq	NSubstitute	KnockOff
Setup getter	mock.Setup(x => x["key"]).Returns(42);	dict["key"].Returns(42);	stub.Indexer["key"].Returns(42);
Dynamic getter	mock.Setup(x => x[It.IsAny<string>()]).Returns(0);	dict[Arg.Any<string>()].Returns(0);	stub.Indexer.Get((key) => 0);
Verify getter	mock.Verify(x => x["key"]);	_ = dict.Received()["key"];	stub.Indexer.VerifyGet();
Verify setter	mock.VerifySet(x => x["key"] = 42);	dict.Received()["key"] = 42;	stub.Indexer.VerifySet();
Predicate match	mock.Setup(x => x[It.Is<string>(k => predicate)]).Returns(42);	dict[Arg.Is<string>(k => predicate)].Returns(42);	stub.Indexer.When(k => predicate).Returns(42);
Per-key verify	mock.Verify(x => x["key"]);	_ = dict.Received()["key"];	stub.Indexer["key"].VerifyGet(Called.Once);
Capture	(manual with Callback)	(manual with When/Do)	stub.Indexer.LastSetEntry (built-in)