SparkyTestHelpers: Moq.Fluent

Brian Schroer
Oct 22, 2018 · 3 min read

part of the “SparkyTestHelpers” suite of .NET unit testing tools

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photo by Paul Glazzard

NuGet package | Source code

I don’t know why it took me so long to try Fluent Assertions for .NET unit testing. I thought it just provided more readable syntax, but it’s way more than that. The test failure messages are much better than MSTest’s Asserts (e.g. telling you exactly where in a long string there’s a difference between expected and actual), and it’s got powerful helpers for verifying expectations for exceptions, DateTime instances and collections.

I’ve been using Fluent Assertions for about two weeks and can’t imagine unit testing without it.

Another tool I can’t imagine testing without is Moq (which is why I created SparkyTestHelpers.Moq earlier this year), so of course, I now want to be able to test Moq fluently.

With the SparkyTestHelpers.Moq.Fluent nuget package, the “out of the box” Moq syntax:

_mock.Verify(x => x.Foo());
_mock.Verify(x => x.Foo(), Times.Once);
_mock.Verify(x => x.Foo(), Times.AtLeastOnce);
_mock.Verify(x => x.Foo(), Times.AtMostOnce);
_mock.Verify(x => x.Foo(), Times.Exactly(3));
_mock.Verify(x => x.Foo(), Times.Between(2, 5));
_mock.Verify(x => x.Foo(), Times.AtLeast(2));
_mock.Verify(x => x.Foo(), Times.AtMost(5));
_mock.Verify(x => x.Foo(), Times.Never);

…can be coded fluently as:

_mock.Should().HaveCallsTo(x => x.Foo());
_mock.Should().HaveOneCallTo(x => x.Foo());
_mock.Should().HaveAtLeastOneCallTo(x => x.Foo());
_mock.Should().HaveAtMostOneCallTo(x => x.Foo());
_mock.Should().HaveCallCount(3).To(x => x.Foo());
_mock.Should().HaveCallCount(2, 5).To(x => x.Foo());
_mock.Should().HaveCallCount(2).OrMore().To(x => x.Foo());
_mock.Should().HaveCallCount(5).OrLess().To(x => x.Foo());
_mock.Should().NoCallsTo(x => x.Foo());

…or as:

_mock.Method(x => x.Foo()).Should().HaveBeenCalled();
_mock.Method(x => x.Foo()).Should().HaveBeenCalledOnce();
_mock.Method(x => x.Foo()).Should().HaveBeenCalledAtLeastOnce();
_mock.Method(x => x.Foo()).Should().HaveBeenCalledAtMostOnce();
_mock.Method(x => x.Foo()).Should().HaveCallCount(3);
_mock.Method(x => x.Foo()).Should().HaveCallCountBetween(2, 5);
_mock.Method(x => x.Foo()).Should().HaveCallCountOfAtLeast(2);
_mock.Method(x => x.Foo()).Should().HaveCallCountOfAtMost(5);
_mock.Method(x => x.Foo()).Should().NotHaveBeenCalled();

There are property Get and Set equivalents for all of the “.Method … .Should… .HaveBeen” methods listed above:

_mock.Get(x => x.Bar).Should().HaveBeenCalledOnce();
_mock.Set(x => x.Bar = “Baz”).Should().HaveBeenCalledOnce();

“It.IsAny” alternate syntax

The package incorporates SparkyTestHelpers.Moq.Core, which enables simplified “Any” syntax:

_mock.Setup(x => x.DoSomething(
It.IsAny<string>(), It.IsAny<int>(),It.IsAny<IEnumerable<int>>())
.Returns(true);

…can be simplified to:

using SparkyTestHelpers.Moq;
. . .
_mock.Setup(x => x.DoSomething(
Any.String, Any.Int, Any.IEnumerable<int>())
.Returns(true);

“Any” members:

  • Any.Action
  • Any.Action<T>
  • Any.Action<T1, T2>
  • Any.Action<T1, T2, T3>
  • Any.Array<T>
  • Any.Boolean
  • Any.Dictionary<TKey, TValue>
  • Any.DateTime
  • Any.Decimal
  • Any.Double
  • Any.Func<T>
  • Any.Func<T1, T2>
  • Any.Func<T1, T2, T3>
  • Any.Guid
  • Any.IEnumerable<T>
  • Any.InstanceOf<T>
  • Any.IList<T>
  • Any.Int
  • Any.IQueryable<T>
  • Any.KeyValuePair<TKey, TValue>
  • Any.Lazy<T>
  • Any.List<T>
  • Any.Long
  • Any.Nullable<T>
  • Any.Object
  • Any.Short
  • Any.Single
  • Any.String
  • Any.TimeSpan
  • Any.Tuple<T1, T2>
  • Any.Type
  • Any.UInt
  • Any.ULong
  • Any.UShort

mock.Where extension method

…provides an alternate syntax for “It.Is”:

using SparkyTestHelpers.Moq;
. . .
// sad:
_mock.Setup(x => x.Foo(It.Is<int>(i => i % 2 == 0))).Returns(true);
// rad!:
_mock.Setup(x => x.Foo(Any.Int.Where(i => i % 2 == 0))).Returns(true);

Reducing code duplication

The Method, Get and Set extensions have properties that return their input expressions/actions, which can be used to reduce code duplication.

For example, this test:

// Arrange:
_mock.Setup(x => x.Foo(
Any.String, Any.Int, Any.InstanceOf<Bar>())
).Returns(true);
// Act:
subjectUnderTest.Foo(“yo”, 5, myBar);
//Assert:
_mock.VerifyOneCallTo(x => x.Foo(
Any.String, Any.Int, Any.InstanceOf<Bar>()));

…where you have to code the same “x => x.Foo(Any.String, Any.Int, Any.InstanceOf<Bar>()” expression for both the .Setup and .Verify calls — can be simplified to:

// Arrange:
var fooCall = _mock.Method(
x => x.Foo(Any.String, Any.Int, Any.InstanceOf<Bar>()))
.Expression;
_mock.Setup(fooCall).Returns(true);// Act:
subjectUnderTest.Foo(“yo”, 5, myBar);
// Assert:
_mock.Method(fooCall).Should().HaveBeenCalledOnce();

Happy testing!

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