Create an MSBuild project and run it, within a unit test.

gistfile1.cs

            var projectRootElement = ProjectRootElement.Create();

            projectRootElement.AddUsingTask(typeof (MyTask));

            projectRootElement
                .AddTarget("Build")
                    .AddTask(typeof(MyTask).Name)
                        .SetParameter("Foo", "hi");

            var highImportanceStringLogger = new HighImportanceStringLogger();

            var success = new ProjectInstance(projectRootElement).Build(new[] { highImportanceStringLogger });
            Assert.IsTrue(success);

            const string expected = @"Inputs:
  Foo = hi
";
            Assert.AreEqual(expected, highImportanceStringLogger.ToString());