public void TestSubsitute()
{
var d = new Dictionary <string, object>();
d["a"] = 1;
Assert.Equal(1, Unifier.Substitute(d, V("a")));
Assert.Equal("b", Unifier.Substitute(d, "b"));
Assert.Equal(new [] { 1 }, Unifier.Substitute(d, new object[] { V("a") }));
Assert.Equal(new [] { "b" }, Unifier.Substitute(d, new object[] { "b" }));
Assert.Equal(new object[] { "b", 1 }, Unifier.Substitute(d, new object[] { "b", V("a") }));
Assert.True(Unifier.Substitute(d, new object[] { "b", V("a") }) is IEnumerable);
Assert.True(new object[] { "b", V("a") } is IEnumerable);
Assert.True(new Stack(new object[] { "b", V("a") }) is IEnumerable);
Assert.True(new Stack(new object[] { "b", V("a") }).Cdr() is IEnumerable);
}