Here is a preview of a new feature that is planned for
SharpDevelop - integrated support for Machine.Specifications.
Machine.Specifications, or MSpec for short, is a
Behaviour Driven Development framework for .NET created by
Aaron Jensen which takes its inspiration from
SpecUnit.NET
and RSpec.
Support for MSpec has been added thanks to
Tomasz Tretkowski.
So let us take a look at how the MSpec integration works in
SharpDevelop.
MSpec Integration
The first thing you will need to do is add a reference to MSpec
in the project that will contain your specifications. The easiest
way to do this is to use NuGet. Select your project, right click
and select Manage Packages.
Search for the Machine.Specifications package and then
click the Add button to add the NuGet package to your
project.
This will add a Machine.Specifications assembly reference to
your project.
Now let us create our first specification. We are going to
create a specification which is based on an
example provided with the MSpec source code. The specification
is for transferring an amount of money between two bank accounts
and is shown below.
using System;
using Machine.Specifications;
namespace Banking.Tests
{
[Subject(typeof(Account), "Funds transfer")]
public class when_transferring_between_two_accounts
{
static Account fromAccount;
static Account toAccount;
Establish context = () => {
fromAccount = new Account { Balance = 1m };
toAccount = new Account { Balance = 1m };
};
Because of = () =>
fromAccount.Transfer(1m, toAccount);
It should_debit_the_from_account_by_the_amount_transferred = () =>
fromAccount.Balance.ShouldEqual(0m);
It should_credit_the_to_account_by_the_amount_transferred = () =>
toAccount.Balance.ShouldEqual(2m);
}
}
MSpec uses Establish/Because/It which is
equivalent to Given/When/Then that is used
with SpecFlow. Establish is used to setup the initial state.
Because is used to define the event/action that you are
testing. It is used to test the final state and see if it
matches what is expected.
The Account class that is used by this specification is shown
below.
using System;
namespace Banking
{
public class Account
{
public decimal Balance { get; set; }
public void Transfer(decimal amount, Account toAccount)
{
}
}
}
Specifications are displayed in the Unit Tests window.
This window can be opened by selecting Unit Tests from the
View | Tools menu. The specification we have defined
will be displayed in the Unit Test window as shown below.
The Unit Tests window will update as the specification is
written in the same way it does when you are writing NUnit
tests.
To run MSpec you can right click a specification and select
Run tests or you can click the toolbar buttons at the top of
the Unit Tests window.
Failures will be highlighted in Red in the Unit Tests window.
The output from MSpec is displayed in the Output
window.
Failures are also added to the Errors window. Clicking on
an error will take you directly to the source code for the failing
test.
Now we have to fix the failures by implementing the
Account's Transfer method. The updated Transfer method is
shown below:
public void Transfer(decimal amount, Account toAccount)
{
Balance -= amount;
toAccount.Balance += amount;
}
After making this change and running MSpec again everything
passes, as shown below.
That completes the quick introduction to using MSpec with
SharpDevelop. Now let us take a look at MSpec Behaviours.
MSpec Behaviours
MSpec Behaviours are a way to group together a set of tests that
you want to re-use with different contexts. To do this you create a
separate class, add a Behaviors attribute to it, and move your
tests into that class. This behaviour class is then referenced by
using the Behaves_like syntax. An example taken from the
MSpec examples is shown below.
using System;
using Machine.Specifications;
namespace Banking.Tests
{
[Subject("Date time parsing")]
public class when_a_date_is_parsed_with_the_regular_expression_parser
: DateTimeParsingSpecs
{
Establish context = () =>
Parser = new RegexParser();
Because of = () =>
ParsedDate = Parser.Parse("2009/01/21");
Behaves_like<DateTimeParsingBehavior> a_date_time_parser;
}
[Subject("Date time parsing")]
public class when_a_date_is_parsed_by_the_infrastructure
: DateTimeParsingSpecs
{
Establish context = () =>
Parser = new InfrastructureParser();
Because of = () =>
ParsedDate = Parser.Parse("2009/01/21");
Behaves_like<DateTimeParsingBehavior> a_date_time_parser;
}
public abstract class DateTimeParsingSpecs
{
protected static DateTime ParsedDate;
protected static IParser Parser;
}
[Behaviors]
public class DateTimeParsingBehavior
{
protected static DateTime ParsedDate;
It should_parse_the_expected_date = () =>
ParsedDate.ShouldEqual(new DateTime(2009, 1, 21));
}
}
Here the behaviour of the parser returning a particular date has
been extracted and re-used across two different contexts.
SharpDevelop is aware of MSpec behaviours and will display the
underlying tests. The date time parser specifications above will be
displayed in the Unit Tests window as shown below.
For further details on MSpec behaviours take a look at the
Behaviours in MSpec post by James Gregory.
Further MSpec Information
Here is a selection of links to further information on MSpec
that you may find useful.
MSpec on Github
Introducing MSpec - Aaron Jensen's post that first
introduced MSpec.
Getting Started with MSpec
Learning
BDD - If you prefer to learn by watching a video check out Rob
Conery's BDD screencast where he discusses BDD and also covers
MSpec.
Make BDD
your BFF - Rob Conery walks through BDD with MSpec.
Teaching a String Calculator How to Behave
Behaviours in MSpec