FunctionalDev.MoqHelpers 3.0.9

FunctionalDev.MoqHelpers

Moq Helpers is a library which has been created to aid unit testing.

Please read through the rest of this document to view tools which can help reduce the brittle nature of unit tests, decrease excess code when setting up objects and enhance the clarity of what it is you're testing.

A particular focus of this library is setting up Mock objects (including non-public members) and providing access to non-public members and methods of instantiated objects.

For a complete changelog, please see the ChangeLog below

Table of Contents

1. Activators - Creating mock objects with less boilerplate code
   1. Lazy Mock Activation - Create abstract mocks with challenging constructor arguments
   2. Lazy Activation - Create complex objects without providing constructor arguments
   3. Container Creation - Encapsulate construction arguments to refer to in tests only if required
2. Object Proxy - Interact with private/protected members (properties, fields, methods and generic methods)
3. Examples
4. Extension Methods
   1. Mock.Setup - Setup mock members with less boilerplate code. Enables the setup protected methods.
   2. ILogger.Unwrap - Provides resolved ILogger invocations in a simple class.
   3. ILogger.Verify - Provides verify methods on ILogger, to be used when verifying a particular log has been invoked.
   4. IEnumerable{T}.Enumerate - Enumerate a collection without storing the results.
   5. IEnumerable{T}.SingleOrThrow - Throw a custom exception if a single match is not found.
   6. Mock.GetInvocations - Extract type cast arguments from a method invocation on a mock.
   7. Mock.PassThrough - Auto-setup all members (fields, properties and methods) for a mock to a given instance.
   8. Type.TryMatchInterface - Determines if a type inherits from a given interface.
   9. Type.MethodSignatureMatch - Can be used to check if a given set of types can be used to invoke a method signature.
5. Full Example
6. Chaining Calls on ActivatedObject / ActivatedObject{T}
7. Changelog

Activators

Creating instances of objects is central to most unit testing. Activator classes have been provided to reduce the overhead and brittle nature of setting up classes, when it may not be required to provide all arguments for the constructor, if those arguments are not necessary for the particular unit test in focus.

These activators can be used to future-proof the creation of objects, in that future changes to an object constructor will not break existing unit tests, providing that the additional arguments do not affect existing behaviour.

Lazy Mock Activation

A MockActivator class can be used to create Mock{T} classes.

This activator has CreateLazy and CreateNull methods which allow the creation of Mock{T} classes without needing to provide all/any constructor arguments.

Whilst these methods can be used to provide all arguments, they can also be provided with some or all constructor arguments to enable future-proofing with future constructor signature changes.

Given the following class:

public abstract class Person
{
  protected Person(ILogger<Person> logger) { }
}

The following example uses CreateLazy, without arguments, to create a new instance of Mock{Person} without supplying an instance of ILogger{Person}. Note that the Person base type will be supplied new Mock{ILogger {Person}}.Object as a value for ILogger{Person}.

public Mock<Person> CreateLazy()
  => MockActivator.CreateLazy<Person>();

The following example uses CreateNull, without arguments, to create a new instance of Mock{Person} without supplying an instance of ILogger{Person}. Note that the Person base type will be supplied null as a value for ILogger{Person}.

public Mock<Person> CreateNull()
  => MockActivator.CreateNull<Person>();

The following example uses CreateLazy, with arguments, to create a new instance of Mock{Person} supplying an instance of Mock{ILogger{Person}}. Note that the Person base type will be supplied loggerMock.Object as a value for ILogger{Person}.

public Mock<Person> CreateLazyWithMockArgument(Mock<ILogger<Person>> loggerMock)
  => MockActivator.CreateLazy<Person>(loggerMock);

The following example uses CreateLazy, with arguments, to create a new instance of Mock{Person} supplying an instance of ILogger{Person}. Note that the Person base type will be supplied loggerInstance as a value for ILogger{Person}.

public Mock<Person> CreateLazyWithMockArgument(ILogger<Person> loggerInstance)
  => MockActivator.CreateLazy<Person>(loggerInstance);

Lazy Activation

A LazyActivator class can be used to create instances of concrete classes.

This activator has CreateLazy and CreateNull methods which allow the creation of concrete classes without needing to provide all/any constructor arguments.

Whilst these methods can be used to provide all arguments, they can also be provided with some or all constructor arguments to enable future-proofing with future constructor signature changes.

An example can be seen below:

public class Person
{
  public Person(ILogger<Person> logger) { }
}

The following example uses CreateLazy, without arguments, to create a new instance of Person without supplying an instance of ILogger{Person}. Note that the Person constructor will be supplied new Mock{ILogger{Person}}.Object as a value for ILogger{Person}.

public Person CreateLazy()
  => LazyActivator.CreateLazy<Person>();

The following example uses CreateNull, without arguments, to create a new instance of Person without supplying an instance of ILogger{Person}. Note that the Person constructor will be supplied null as a value for ILogger{Person}.

public Person CreateNull()
  => LazyActivator.CreateNull<Person>();

The following example uses CreateLazy, with arguments, to create a new instance of Person supplying an instance ofMock{ILogger{Person}}. Note that the Person constructor will be supplied loggerMock.Object as a value for ILogger{Person}.

public Person CreateLazyWithMockArgument(Mock<ILogger<Person>> loggerMock)
  => LazyActivator.CreateLazy<Person>(loggerMock);

The following example uses CreateLazy, with arguments, to create a new instance of Person supplying an instance of ILogger{Person}. Note that the Person constructor will be supplied loggerInstance as a value for ILogger{Person}.

public Person CreateLazyWithMockArgument(ILogger<Person> loggerInstance)
  => LazyActivator.CreateLazy<Person>(loggerInstance);

Container Creation

Container Lazy and Mock activation has been added to provide a means of extracted auto loaded construction objects. Please note that whilst this example uses MockActivator this is also present in LazyActivator.

private readonly TestClass _testClass;
private readonly Mock<ILogger<TestClass>> _loggerMock;
private readonly Mock<IWidget> _widgetMock;
private readonly IWidget _widget;

public UnitTest()
{
    var container = MockActivator.CreateLazyContainer<TestClass>();

    _testClass = container.Instance.Object;
    _loggerMock = container.GetArgumentAsMock<ILogger<TestClass>>();
    _widgetMock = container.GetArgumentAsMock<IWidget>();
    _widget = container.GetArgument<IWidget>();
}

Object Proxy

The ObjectProxy class can be used to interact (set/get) private members of a given instance, and can be used to invoke protected/private methods.

Dot separated member access is supported to access members of members recursively. E.g. ObjectProxy.For(person)["Name"."FirstName"]

Static classes can be setup with ObjectProxy.ForStatic to interact with static classes.

Examples

Given the following class:

public class Person
{
  private string Name { set; get; }

  private Person(ILogger<Person> logger, string name)
  {
    Name = name;
  }

  private string GetName()
    => Name;

  private string ToStringFor<T>(T arg)
    => arg.ToString();
}

Creating an instance of Person can be achieved as shown below.

var person = LazyActivator.CreateLazy<Person>("Fred");
// or
var person = LazyActivator.CreateLazy<Person>();

And members can be managed as shown below.

// Get.
var name = ObjectProxy.For(person)["Name"];

// Set.
ObjectProxy.For(person)["Name"] = "Bob";

Methods can be invoked via the proxy with:

var result = person.InvokeMethod<string>("GetName");

For full examples please see end of this file.

Extension Methods

Mock.Setup

Several extension methods have been provided which enable functional Moq creation (returning Mock{T} to enable chaining) and to setup private/protected members.

Please note that to resovle the extension methods, it may be required to add the following using statement:

using FunctionalDev.MoqHelpers;

Please also note that the extension methods are not the typical .Setup(...).Returns(...) format. For simple method setups the format this library provides is:

.Setup(type => type.MethodName, Expression<Func<InputArgs, ReturnArg>>);

Given an example interface:

public interface IPerson
{
    string SetName(string name);
    int GetAge();
}

The following can be used to set up an IPerson interface.

var person = new Mock<IPerson>()
    .Setup(x => x.SetName, (string name) => "")
    .Setup(x => x.GetAge, () => 25);

Please note that this does not provide any filters on the arguments for methods (such as It.Is<T>(Func<T, bool>) filtering).

ILogger.Unwrap

Mock{ILogger}.Unwrap() is an extension method which returns a set of resolved invocations on the logger.

This can be used when it is required to manually inspect the invocations of a ILogger Mock.

For example, given the following code snippet:

var loggerMock = new Mock<ILogger<ExampleClass>>();
loggerMock.Object.LogError("Error log example");
loggerMock.Object.LogDebug("Debug log example");

loggerMock.Unwrap().ToList().ForEach(loggerArguments =>
{
    Console.WriteLine($"Level: '{loggerArguments.Level}'");
    Console.WriteLine($"Message: '{loggerArguments.Message}'");
    Console.WriteLine($"Exception: '{loggerArguments.Exception?.Message}'");
    Console.WriteLine();
});

Output:

Level: 'Error'
Message: 'Error log example'
Exception: ''

Level: 'Debug'
Message: 'Debug log example'
Exception: ''

ILogger.Verify

Mock{ILogger{T}}.Verify(...) are a series of extension methods which can be used to verify that an ILogger has been invoked for a particular ErrorLog, Times and message.

A combination of ErrorLog, message text, and Times can be used to ensure that a particular log has been invoked. Additionally a Func<string, ErrorLog, bool> can be used to have full control over the verification.

IEnumerable{T}.Enumerate

It is sometimes required during unit testing to ensure that an enumerable set has been enumerated (to ensure the collection is valid) before continuing with any assertions, for example the result of a method target. Call IEnumerable{T}.Enumerate() to fully iterate through a given collection without assigning references to any of the items.

IEnumerable{T}.SingleOrThrow

IEnumerable{T}.SingleOrThrow can be used to pull a single object of T from a given collection. If exactly one object is not found then a custom exception is thrown, as provided in the call.

Mock.GetInvocations

Mock.GetInvocations<T1...T10>(string/MethodInfo) can be used to return type cast method invocations from a given mock.

Mock.PassThrough

Mock.PassThrough can be used to auto-setup all members (fields, properties and methods) for a mock to a given instance.

Note that for a mock setup this way it will be possible to override setup methods if required, as well as effectively using a mock to capture invoked members of a given instance.

Type.TryMatchInterface

Type.TryMatchInterface can be used to determine if a given type inherits from a given interface.

Type.MethodSignatureMatch

Type.MethodSignatureMatch can be used to compare two type arrays and checks that the second set can be used to invoke a method whose signature matches the first set.

Full Example

public abstract record FullExampleObjectBase(ILogger<FullExampleObjectBase> Logger)
{
    public ILogger<FullExampleObjectBase> Logger { get; } = Logger;

    private int _localIntegerValue = 1;

    protected virtual string GetName()
        => nameof(FullExampleObjectBase);

    private void SetLocalIntegerValue(int newValue)
    {
        _localIntegerValue = newValue;
    }

    private int GetLocalIntegerValue()
        => _localIntegerValue;

    private int GenericMethod<T>() => 1;

    public abstract string GetNameAbstract(string arg);
}

public record FullExampleObject(ILogger<FullExampleObjectBase> Logger)
    : FullExampleObjectBase(Logger)
{
    public override string GetNameAbstract(string arg)
        => arg;
}

public static class FullExampleStaticClass
{
    private static void SetStaticValue(string arg) { }
}

public class FullExample
{
    public FullExampleObject CreateFullExampleObject()
        => LazyActivator.CreateLazy<FullExampleObject>();

    public FullExampleObject CreateFullExampleObjectWithArgument()
        => LazyActivator.CreateLazy<FullExampleObject>(Mock.Of<ILogger<FullExampleObjectBase>>());

    public void SetPrivate()
    {
        var proxy = ObjectProxy.For(CreateFullExampleObject());
        proxy["_localIntegerValue"] = 5;
    }

    public void GetPrivate()
    {
        var proxy = ObjectProxy.For(CreateFullExampleObject());
        var value = (int)proxy["_localIntegerValue"];
    }

    private void CallPrivate()
    {
        var proxy = ObjectProxy.For(CreateFullExampleObject());
        proxy.InvokeMethod("SetLocalIntegerValue", 5);
    }

    private void CallPrivateWithReturning()
    {
        var proxy = ObjectProxy.For(CreateFullExampleObject());
        int resultAsInt = proxy.InvokeMethod<int>("GetLocalIntegerValue");
        object resultAsObject = proxy.InvokeMethod("GetLocalIntegerValue");
    }

    private void CallGenericPrivateMethod()
    {
        var proxy = ObjectProxy.For(CreateFullExampleObject());
        int resultAsInt = proxy.InvokeGenericMethod<int>("GenericMethod", new[] { typeof(RecordClass) }, Array.Empty<object>());
        object resultAsObject = proxy.InvokeGenericMethod("GenericMethod", new[] { typeof(RecordClass) }, Array.Empty<object>());
    }

    private void ObjectProxyForStaticClass()
    {
        var proxy = ObjectProxy.ForStatic(typeof(FullExampleStaticClass));
        proxy.InvokeMethod("SetStaticValue", "Hello world");
    }

    private void SetupExtensionMethods()
    {
        MockActivator.CreateLazy<FullExampleObjectBase>()
            // Setting members.
            .Setup(x => x.Logger, Mock.Of<ILogger<FullExampleObjectBase>>())
            // Setting public methods.
            .Setup(x => x.GetNameAbstract, (string arg) => arg + "test")
            // Setting private methods.
            .Setup("GetName", () => "Hello World")
            // Also works for public methods.
            .Setup("GetNameAbstract", (string arg) => arg + "test")
            ;
    }
}

Chaining Calls on ActivatedObject/ActivatedObject{T}

Further changes in containers allows for chaining setups:

var container = LazyActivator.CreateLazyContainer<MyTestClass>()
  .SetupMock<IWidget>(widget => { })
  .SetupMock<ITestObject>(testObject => testObject.Setup(x => x.Name, "Fred"))
  .SetupMock<ITestObject>(testObject => testObject.Setup(x => x.Name, "Frank"))
  .Arguments
      .AddToArgumentCollection(new Mock<ILogger<MyTestClass>>().Object)
      .Parent
  .SetupMock<ILogger<MyTestClass>>(logger =>
  {
      logger.Setup(...)
  });

ChangeLog

3.0.9 | 14/04/2023

• Added extensions to readme

3.0.8 | 14/04/2023

• Fixed readme TOC

3.0.7 | 14/04/2023

• Fixed ActivatedObject.GetArgument<TClass>() returning null.

3.0.6 | 17/02/2023

• Added ConvertToInstanceType extension to convert from ActivatedObject<Mock<T>> to ActivatedObject<T>.

3.0.5 | 16/02/2023

• Fixed a bug in Mock<ILogger>.Verify() where a particular execution path recursively calls itself and causes a stack overflow.

3.0.4 | 07/02/2023

• Fixed a bug in Mock<ILogger>.Unwrap() where a non Log method invocation has occured.

3.0.3 | 07/02/2023

• Added support for .NET 6

3.0.2 | 24/01/2023

• Reversed previous obsolete flag additions

3.0.1 | 11/01/2023

• Introduced ChangeLog

3.0.0 | 11/01/2023

• Breaking - ActivatedObject{T} no longer inherits from ActivatedObject, instead a new base class has been introduced (ActivatedObjectBase) which they both share.
• Breaking - The two methods GetArgument and GetArgumentAsMock have been marked as obsolete (and have been moved to ActivatedObjectBase) and may be removed on the next major release.
• Breaking - ActivatedObject no longer has a property called InstanceUnTyped it has been renamed to Instance with a type of object, mirroring the property on ActivatedObject{T} named Instance of type T (class generic type).
• Added chaining calls to ActivatedObjects to enable setting up of mocks inline/chained.
• Rewrite on the argument logic allowing custom injection of objects after instantiation.
• Updated all ILogger{T} extension methods to also support ILogger.
• Logger/Logger{T}.Unwrap() now returns the exception, if provided on invocations.