Base Pattern Unit Tests

A BasePattern takes 13 or 14 tiles and groups them into melds, feeding the result to the std patterns for yaku recognition. It also computes shanten. BaseTest gives you two convenience helpers — Resolve and Shanten — to test both jobs.

Testing decomposition with Resolve

[TestClass]
public class Base33332Test : BaseTest {
    protected override BasePattern V { get; set; } = new Base33332();

    [TestMethod]
    public void TestShun() {
        Assert.IsTrue(Resolve("122334sr5677p", "7p", "567p"));
        Assert.IsFalse(Resolve("122334s5567p", "7p", "567p"));
    }
}

Here we test sequence decomposition. The first hand is:

Matches the 33332 shape → Resolve returns true

Because it fits 33332, Resolve should return true — the shape was parsed successfully. The second hand is:

Does not match 33332 → Resolve returns false

This one doesn't fit 33332, so Resolve should return false.

Resolve API

The first two arguments are required — the hand and the winning tile. After that you may add any number of arguments for fixed melds (called melds or concealed kans). Some examples:

Assert.IsTrue(Resolve("2z", "2z", "1111s", "1111p", "1111m", "1111z"));

Four concealed kans + a pair, winning on 2z

Assert.IsTrue(Resolve("6666666666666z", "6z"));

Thirteen 6z + winning 6z

Testing shanten with Shanten

[TestClass]
public class Base33332Test : BaseTest {
    protected override BasePattern V { get; set; } = new Base33332();

    [TestMethod]
    public void TestShanten1() {
        Assert.AreEqual(0, Shanten("2233445566778s", null));
        tiles.AssertEquals("258s");
    }

    [TestMethod]
    public void TestShanten2() {
        Assert.AreEqual(5, Shanten("25569m2589p5s357z", "3s", 5));
        tiles.AssertEquals("2569m25p357z");
    }
}

Shanten API

Shanten takes almost the same arguments as Resolve (plus an optional maximum shanten). It returns the shanten of the given hand and sets the tiles field. The second argument changes what tiles means:

• If the second argument is null (13 tiles total), tiles = every tile that reduces shanten (the useful draws / 進張).
• If the second argument is non-null (14 tiles total), tiles = every discard that leaves shanten equal to the returned value.

So the two tests mean:

• is already tenpai, waiting on .

• is 5-shanten; you can discard any of to stay at 5.

When the hand is already complete

For 14 tiles that already form a winning hand, shanten is $-1$ and tiles is empty:

Assert.AreEqual(-1, Shanten("1s", "1s", 8, "222s", "345s", "111p", "111z"));
tiles.AssertEquals("");

Here the third argument 8 means "resolve up to 8 shanten at most".

The maxShanten argument

In practice maxShanten optimizes computation. If you only need to know whether a hand is at most 1-shanten, you can stop searching once shanten exceeds 1 rather than computing the exact number.

This example is:

Already a winning hand (shanten = -1)

Early termination

If the shanten is known to exceed the limit, Shanten returns int.MaxValue and sets tiles to null:

Assert.AreEqual(int.MaxValue, Shanten("25569m2589p5s357z", null, 5));
Assert.IsNull(tiles);

This example is:

Shanten exceeds 5 → search terminates early