dotCover config file for command line NUnit test coverage

So you want to produce a coverage report for your .Net project, preferably from the command line? If you use dotCover and NUnit then this:

<?xml version="1.0" encoding="utf-8"?>
<AnalyseParams>
    <Executable><!-- Path to your NUnit bin directory e.g.  -->C:\Program Files\NUnit 2.5.10\bin\net-2.0\nunit-console.exe</Executable>
    <WorkingDir><!-- This path works for running dotCover with a config file in the project directory-->bin\Debug\</WorkingDir>
    <Arguments><!-- The dlls containing NUnit tests. Space delimited if more than one-->My.Tests.dll My.MoreTests.dll</Arguments>
    <Output><!-- Path to where I want the report. Can be relative or absolute -->My.Tests.Coverage.html</Output>
    <Filters>
        <IncludeFilters>
            <FilterEntry><!--  _ "Module" means project _ --><ModuleMask>*</ModuleMask></FilterEntry>
        </IncludeFilters>
        <ExcludeFilters>
            <FilterEntry><!--  _ "Module" means project _ --><ModuleMask>My.Tests</ModuleMask></FilterEntry>
            <FilterEntry><!-- namespaces can be filter with a ClassMask with * wildcard --><ClassMask>Namespaces.For.AutogeneratedCode.*</ClassMask></FilterEntry>
            <FilterEntry><ClassMask>SomeUntestable.Class</ClassMask></FilterEntry>
        </ExcludeFilters>
    </Filters>
    <ReportType>html</ReportType>
 </AnalyseParams>

will allow you, from the command line, to type:

dotCover analyse MyConfigFileName.xml

and generate coverage reports. Assuming that dotCover is in your path of course.
I like to set the filters to exclude coverge report on the test project itself as well as autogenerated code.

Covering Multiple Test Projects In One Run

  • Set your working directory to be a parent of all the test projects, e.g. the solution directory.
  • List the full relative paths to each Test dll, space limited:
    <WorkingDir>.</WorkingDir>
    <Arguments>Web.Tests\bin\Debug\MyProject.Web.Tests.dll Implementation.Tests\bin\Debug\MyProject.Implementation.Tests.dll</Arguments>

Filtering and more advanced coverage configs

  • Look down the right hand side of the page here : http://www.jetbrains.com/dotcover/documentation/index.html for documentation, such as it is.
  • Filtering is covered here: http://blogs.jetbrains.com/dotnet/2010/07/filtering-with-dotcover/
  • More complex stuff is touched on here: http://blogs.jetbrains.com/dotnet/tag/code-coverage/

The Object Quote Pattern for Testability of Components with Dependencies

I hereby introduce a very simple no-configuration pattern for making components with dependencies unit testable. Object Quote competes with existing solutions for testability of components with dependencies and is intended to be the simplest possible solution. This will make most sense if you already understand the problem of unit testing components and classes with dependencies.

Existing Patterns for Unit Testability

  • Dependency Injection or Service Location use a DI Container or a Service Locator for runtime configurability. As a side effect, they also provides a solution, albeit rather heavyweight, for test-time mockability
  • The Humble Object Pattern is an approach for codebases built without DI or service locator. A class with dependencies is refactored into two classes, one of which sets up the dependencies on the other, which contains the meat (or logic) of the class. The class containing the logic is then testable.

Neither of these are cost-free. Dependency Injection requires a framework and is best considered as an application-wide architectural pattern that should be used when runtime configuration is required. In that sense it is overkill for most bespoke code where you don’t need to choose at runtime between multiple implementations for an interface, and all you want is test-time mockability.

The humble object is effectively a proposal to rewrite code, albeit minimally. So it has a significant cost to it; and the end result is slightly more complex than the original.

The Object Quote Pattern

is very simple. It requires no framework, and can be applied to existing code for virtually no startup cost.

  1. Merrily write (or read, if it’s already written) your code with hard coded dependencies.
  2. Uncouple the dependencies by quoting the hard-coded references with a “Soq” – a simple object quoter.
  3. In your unit tests, configure the Soq as a Moq Soq.

Behold. You now have decoupled, testable code. Thus:

public class MyClassThatDependsonSomething
{
	public SomeDependency  D1 { get; set; }

    public MyClassThatDependsonSomething()
    {
        D1 = Soq.Quote( new SomeDependency() );
    }
}

[TestFixture]
public class TestExampleCode
{
    [Test]
    public void Test_something_with_dependencies()
    {
        //Arrange
        SomeDependency dummy = new Mock<SomeDependency>().Object;

        var mockSoq = new Mock<Soq>();
        mockSoq.Setup(soq => soq.QuoteImplementation<SomeDependency>(It.IsAny<SomeDependency>()))
                .Returns(dummy);
        Soq.ConfigureForTest(mockSoq.Object);

        // Act
        var myClass = new MyClassThatDependsonSomething();
        var result = myClass.D1;

        //Assert
        Assert.AreSame<SomeDependency>(dummy, result);
    }
}

How it works

By default the Soq just returns the object given it.
But when configured for test, the Soq is implemented by your MoqSoq, which returns whatever you’ve configured it to.

Voila. Testable code with no framework needed and no extensive refactoring of existing codebase. You get started with TDD even on legacy code with minimal overhead.

Get the code and a couple of example tests from https://github.com/xcarroll/Soq. Or copy and paste the source — just 12 lines of actual code  — from below.

The Soq Class

On Github: https://github.com/xcarroll/Soq/blob/master/Soq.cs

using System;
public class Soq
{
        private static Soq instance = new Soq();

        public static T Quote<T>(T instantiatedDependency)
        {
            return instance.QuoteImplementation<T>(instantiatedDependency);
        }

        public virtual T QuoteImplementation<T>(T dependency)
        {
            return dependency;
        }

        public static void ConfigureForTest(Soq testSoq)
        {
            if (!ConfigurationIsEnabled)
            {
                throw new InvalidOperationException(
                 "Test configuration is not enabled.");
            }
            instance = testSoq ?? new Soq();
        }
        public static bool ConfigurationIsEnabled { get { return true; } }
}

Highly Unlikely — The Mark of the Beast Bug

In 1991, amongst a series of theorems about rounding in floating point arithmetic calculations, the author parenthetically noted that rounding a number to 53 significant digits, and then rounding it again to 52 significant digits, might produce a different answer compared to when you do the rounding to 52 digits all in one go. He all but apologised for the parenthesis, noting it was “highly unlikely to affect any practical program adversely.”

19 years and 10 months later a researcher discovered that the “Mark of the Beast Bug” could freeze almost any computer in the world, and that millions of webservers could be taken down by it almost at the touch of a button — because of an error when rounding a very very small number, first to 53 significant digits, and then to 52.