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 IsCoalesceStringLifted ()
		{
			var coalesce = Expression.Coalesce (
				Expression.Parameter (typeof (string), "a"),
				Expression.Parameter (typeof (string), "b"));

			Assert.AreEqual ("(a ?? b)", coalesce.ToString ());

			Assert.IsFalse (coalesce.IsLifted);
			Assert.IsFalse (coalesce.IsLiftedToNull);
		}

		[Test]
		public void IsCoalesceNullableIntLifted ()
		{
			var coalesce = Expression.Coalesce (
				Expression.Parameter (typeof (int?), "a"),
				Expression.Parameter (typeof (int?), "b"));

			Assert.IsFalse (coalesce.IsLifted);
			Assert.IsFalse (coalesce.IsLiftedToNull);
		}

		[Test]
		public void CoalesceNullableInt ()
		{
			var a = Expression.Parameter (typeof (int?), "a");
			var b = Expression.Parameter (typeof (int?), "b");
			var coalesce = Expression.Lambda<Func<int?, int?, int?>> (
				Expression.Coalesce (a, b), a, b).Compile ();

			Assert.AreEqual ((int?) 1, coalesce (1, 2));
			Assert.AreEqual ((int?) null, coalesce (null, null));
			Assert.AreEqual ((int?) 2, coalesce (null, 2));
			Assert.AreEqual ((int?) 2, coalesce (2, null));
		}

		[Test]
		public void CoalesceString ()
		{
			var a = Expression.Parameter (typeof (string), "a");
			var b = Expression.Parameter (typeof (string), "b");
			var coalesce = Expression.Lambda<Func<string, string, string>> (
				Expression.Coalesce (a, b), a, b).Compile ();

			Assert.AreEqual ("foo", coalesce ("foo", "bar"));
			Assert.AreEqual (null, coalesce (null, null));
			Assert.AreEqual ("bar", coalesce (null, "bar"));
			Assert.AreEqual ("foo", coalesce ("foo", null));
		}

		[Test]
		public void CoalesceNullableToNonNullable ()
		{
			var a = Expression.Parameter (typeof (int?), "a");

			var node = Expression.Coalesce (a, Expression.Constant (99, typeof (int)));

			Assert.AreEqual (typeof (int), node.Type);
			Assert.IsFalse (node.IsLifted);
			Assert.IsFalse (node.IsLiftedToNull);

			var coalesce = Expression.Lambda<Func<int?, int>> (node, a).Compile ();

			Assert.AreEqual (5, coalesce (5));
			Assert.AreEqual (99, coalesce (null));
		}
	}
}