public void ReplaceIfNull()
        {
            var bd1 = new BooleanDisposable();
            var bd2 = new BooleanDisposable();

            var field = default(IDisposable);

            Assert.True(DisposableHelper.ReplaceIfNull(ref field, bd1));

            Assert.False(bd1.IsDisposed());
            Assert.False(bd2.IsDisposed());

            Assert.False(DisposableHelper.ReplaceIfNull(ref field, bd2));

            Assert.False(bd1.IsDisposed());
            Assert.False(bd2.IsDisposed());

            Assert.True(DisposableHelper.Dispose(ref field));

            Assert.True(bd1.IsDisposed());
            Assert.False(bd2.IsDisposed());

            var bd3 = new BooleanDisposable();

            Assert.False(DisposableHelper.SetIfNull(ref field, bd3));

            Assert.True(bd3.IsDisposed());
        }
        public void SetIfNull_Null()
        {
            try
            {
                var field = default(IDisposable);

                DisposableHelper.SetIfNull(ref field, null);
                Assert.Fail("Should have thrown");
            }
            catch (ArgumentNullException)
            {
                // expected
            }
        }