mono/mcs/class/System.Core/Test/System.Linq.Expressions/ExpressionTest_Coalesce.cs

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// Authors:
//		Federico Di Gregorio <[email protected]>

using System;
using System.Reflection;
using System.Linq;
using System.Linq.Expressions;
using NUnit.Framework;

namespace MonoTests.System.Linq.Expressions
{
	[TestFixture]
	public class ExpressionTest_Coalesce
	{
		[Test]
		[ExpectedException (typeof (ArgumentNullException))]
		public void Arg1Null ()
		{
			Expression.Coalesce (null, Expression.Constant (1));
		}

		[Test]
		[ExpectedException (typeof (ArgumentNullException))]
		public void Arg2Null ()
		{
			Expression.Coalesce (Expression.Constant (1), null);
		}

		[Test]
		[ExpectedException (typeof (InvalidOperationException))]
		public void NonNullLeftParameter ()
		{
			// This throws because they are both doubles, which are never
			Expression.Coalesce (Expression.Constant (1.0), Expression.Constant (2.0));
		}

		[Test]
		[ExpectedException (typeof (ArgumentException))]
		public void Incompatible_Arguments ()
		{
			// The artuments are not compatible
			Expression.Coalesce (Expression.Parameter (typeof (int?), "a"),
					     Expression.Parameter (typeof (bool), "b"));
		}

		[Test]
		public void Coalesce_1 ()
		{
			// Build the expression by hand for now:
			ParameterExpression pa = Expression.Parameter (typeof (int?), "a");
			ParameterExpression pb = Expression.Parameter (typeof (int?), "b");
			BinaryExpression c = Expression.Coalesce (pa, pb);
			Assert.AreEqual ("(a ?? b)", c.ToString ());

			Expression<Func<int?, int?, int?>> e = Expression.Lambda<Func<int?,int?,int?>>(
				c, new ParameterExpression [] { pa, pb });
			Assert.AreEqual ("(a, b) => (a ?? b)", e.ToString ());

			Func<int?,int?,int?> comp = e.Compile ();

			Assert.AreEqual (10, comp (10, 20));
		}
	}
}