private static void TestRightIdentityRule <M>(IMonadBuilder <int, M> builder) where M : IMonad <int>
{
var value = 1;
var monad = builder.BuildFrom(value);
Assert.AreEqual(
monad,
monad.FlatMap(v => builder.BuildFrom(v), builder),
$"Type '{typeof(M)}' doesn't obey the right identity rule of monads"
);
}
private static void TestLeftIdentityRule <M>(IMonadBuilder <int, M> builder) where M : IMonad <int>
{
var value = 1;
var monad = builder.BuildFrom(value);
IMonad <int> f(int i) => builder.BuildFrom(i * 2);
Assert.AreEqual(
monad.FlatMap(f, builder),
f(value),
$"Type '{typeof(M)}' doesn't obey the left identity rule of monads"
);
}
private static void TestAssociativityRule <M>(IMonadBuilder <int, M> builder) where M : IMonad <int>
{
var value = 1;
var monad = builder.BuildFrom(value);
IMonad <int> f(int i) => builder.BuildFrom(i * 2);
IMonad <int> g(int i) => builder.BuildFrom(i + 6);
Assert.AreEqual(
monad.FlatMap(f, builder).FlatMap(g, builder),
monad.FlatMap(v => f(v).FlatMap(g, builder), builder),
$"Type '{typeof(M)}' doesn't obey the associativity rule of monads"
);
}
public static void TestMonadType <M>(IMonadBuilder <int, M> builder) where M : IMonad <int>
{
TestLeftIdentityRule(builder);
TestRightIdentityRule(builder);
TestAssociativityRule(builder);
}
