JoshHeaps.Net/tests/holdem/deadButton.test.js

// The button when somebody gets up out of the blinds.
//
// Passing the button to the next *player* is right until a chair between the button
// and the blinds empties. Then it pulls the whole blind order forward a place: the
// player after the empty chair is never asked for a big blind, and the one after them
// is asked an orbit early. The dead button rule holds the rotation to the seats for
// one hand so the big blind still advances exactly one player.
const test = require("node:test");
const { describe } = require("node:test");
const assert = require("node:assert");
const { HoldemState, Betting, makeTable } = require("./load");

// Four players in six chairs: Ann 0, Ben 1, Cal 2, Dee 3.
const NAMES = ["Ann", "Ben", "Cal", "Dee"];
const table = (dealerSeatIndex = 0) => {
    const state = makeTable({ seatCount: 6, seated: [0, 1, 2, 3], stack: 200, dealerSeatIndex });
    NAMES.forEach((name, i) => { state.seats[i].name = name; });
    return state;
};

const nameOf = (state, index) =>
    index === null || index === undefined ? null : (state.seats[index].name || `empty seat ${index + 1}`);

const blinds = state => {
    const { sbIndex, bbIndex } = HoldemState.getBlindSeats(state);
    return { sb: nameOf(state, sbIndex), bb: nameOf(state, bbIndex) };
};

const leave = (state, index) => {
    state.seats[index].name = "";
    state.seats[index].inHand = false;
    state.seats[index].stack = 0;
    state.seats[index].buyIns = 0;
};

describe("somebody gets up out of the blinds", () => {
    test("the small blind leaves: dead button, and the big blind still moves one player", () => {
        const state = table(1);                 // button Ben, small Cal, big Dee
        Betting.beginHand(state);
        assert.deepEqual(blinds(state), { sb: "Cal", bb: "Dee" });

        leave(state, 2);                        // Cal takes their chips and goes
        HoldemState.startNextHand(state);
        Betting.beginHand(state);

        assert.equal(state.dealerSeatIndex, 2, "the button holds Cal's empty chair");
        assert.equal(state.seats[2].inHand, false, "which is the point — it's on nobody");
        assert.deepEqual(blinds(state), { sb: "Dee", bb: "Ann" },
            "Dee moves from big to small and Ann posts the big blind, one player along");
    });

    test("and Ann is not skipped, which is the money in it", () => {
        // The old rotation passed the button to the next player, which made the blinds
        // Ann/Ben — Ann never posting a big blind at all, and Ben posting one an orbit
        // early. That is a real big blind out of a real player's stack.
        const state = table(1);
        Betting.beginHand(state);
        leave(state, 2);
        HoldemState.startNextHand(state);

        assert.equal(blinds(state).bb, "Ann", "Ann owes the big blind and still owes it");
    });

    test("the big blind leaves: no small blind is posted this hand", () => {
        const state = table(1);                 // button Ben, small Cal, big Dee
        Betting.beginHand(state);

        leave(state, 3);                        // Dee goes
        HoldemState.startNextHand(state);
        Betting.beginHand(state);

        const { sbIndex, bbIndex, deadSmallBlind } = HoldemState.getBlindSeats(state);
        assert.equal(state.dealerSeatIndex, 2, "the button reaches Cal as it was always going to");
        assert.equal(sbIndex, null, "the small blind is dead");
        assert.equal(deadSmallBlind, true, "and says so, rather than looking like a table with no blinds");
        assert.equal(nameOf(state, bbIndex), "Ann", "the big blind still moves on one player");
    });

    test("a dead small blind still deals a hand, with one blind in the middle", () => {
        const state = table(1);
        Betting.beginHand(state);
        leave(state, 3);
        HoldemState.startNextHand(state);
        Betting.beginHand(state);

        assert.equal(state.bettingOpen, true, "the hand goes ahead");
        const posted = state.seats.reduce((sum, p) => sum + Betting.committed(p), 0);
        assert.equal(posted, state.bigBlind, "just the big blind, and nothing conjured to stand in for the small");
        assert.equal(state.currentBet, state.bigBlind);
        assert.ok(state.actingSeatIndex !== null, "and somebody is on the clock");
    });

    test("somebody leaving from anywhere else changes nothing", () => {
        const state = table(1);                 // button Ben, small Cal, big Dee
        Betting.beginHand(state);

        leave(state, 0);                        // Ann, who was under the gun
        HoldemState.startNextHand(state);

        assert.equal(state.dealerSeatIndex, 2, "the button passes to Cal exactly as before");
        assert.equal(state.deadButton, false);
        assert.equal(state.deadSmallBlind, false);
        assert.deepEqual(blinds(state), { sb: "Dee", bb: "Ben" });
    });
});

describe("the ordinary rotation is untouched", () => {
    test("a full table passes the button one player at a time", () => {
        const state = table(0);
        const seen = [];
        for (let hand = 0; hand < 8; hand++) {
            Betting.beginHand(state);
            seen.push(blinds(state).bb);
            HoldemState.startNextHand(state);
        }
        assert.deepEqual(seen, ["Cal", "Dee", "Ann", "Ben", "Cal", "Dee", "Ann", "Ben"],
            "two clean orbits, everybody paying one big blind per orbit");
        assert.equal(state.deadButton, false);
        assert.equal(state.deadSmallBlind, false);
    });

    test("players spread thinly around a big table don't create dead positions", () => {
        // Three players in nine chairs. The chairs between them were never in the
        // rotation, so holding to seats there would post blinds to nobody hand after
        // hand — which is why the button follows players, not chairs, by default.
        const state = makeTable({ seatCount: 9, seated: [0, 4, 7], stack: 200, dealerSeatIndex: 0 });
        ["Ann", "", "", "", "Ben", "", "", "Cal"].forEach((n, i) => { state.seats[i].name = n; });

        const seen = [];
        for (let hand = 0; hand < 6; hand++) {
            Betting.beginHand(state);
            const { sbIndex, bbIndex } = HoldemState.getBlindSeats(state);
            assert.ok(state.seats[sbIndex].inHand, "a real player posts the small blind");
            assert.ok(state.seats[bbIndex].inHand, "and a real player the big");
            seen.push(nameOf(state, bbIndex));
            HoldemState.startNextHand(state);
        }
        assert.deepEqual(seen, ["Cal", "Ann", "Ben", "Cal", "Ann", "Ben"], "one big blind each per orbit");
    });

    test("pressing next hand twice without dealing just passes the button along", () => {
        const state = table(0);
        Betting.beginHand(state);

        HoldemState.startNextHand(state);
        assert.equal(state.dealerSeatIndex, 1);
        HoldemState.startNextHand(state);
        assert.equal(state.dealerSeatIndex, 2, "and doesn't rotate off the same hand twice");
    });
});

describe("the rule knows where it stops", () => {
    test("down to two players, heads-up takes over and nothing is left dead", () => {
        const state = table(1);
        Betting.beginHand(state);
        leave(state, 2);
        leave(state, 3);                        // both blinds walk at once

        HoldemState.startNextHand(state);
        Betting.beginHand(state);

        const { sbIndex, headsUp } = HoldemState.getBlindSeats(state);
        assert.equal(headsUp, true);
        assert.equal(sbIndex, state.dealerSeatIndex, "heads-up the button posts the small blind");
        assert.ok(state.seats[state.dealerSeatIndex].inHand, "and the button is on a player again");
    });

    test("a button stranded by accident is still rescued", () => {
        // Not the dead button: nobody left out of the blinds, the chair the button is
        // on just emptied. That one does want putting back on a player.
        const state = table(3);
        state.seats[3].inHand = false;
        HoldemState.ensureButtonOnPlayer(state);
        assert.ok(state.seats[state.dealerSeatIndex].inHand);
    });

    test("moving the button by hand clears the dead positions", () => {
        const state = table(1);
        Betting.beginHand(state);
        leave(state, 2);
        HoldemState.startNextHand(state);
        assert.equal(state.deadButton, true);

        // What the seat menu's "Give the button" does.
        state.dealerSeatIndex = 0;
        state.deadButton = false;
        state.deadSmallBlind = false;
        Betting.beginHand(state);

        const { sbIndex } = HoldemState.getBlindSeats(state);
        assert.ok(state.seats[sbIndex].inHand, "a real small blind again, where the dealer put it");
    });

    test("naming a blind by hand overrules a dead one", () => {
        const state = table(1);
        Betting.beginHand(state);
        leave(state, 3);
        HoldemState.startNextHand(state);
        assert.equal(state.deadSmallBlind, true);

        state.blindOverride = { sbIndex: 1, bbIndex: 0 };
        const { sbIndex, bbIndex, manual } = HoldemState.getBlindSeats(state);
        assert.equal(manual, true);
        assert.equal(sbIndex, 1, "the dealer's word beats the rule");
        assert.equal(bbIndex, 0);
    });

    test("a table saved before any of this reads as nothing dead", () => {
        const state = table(0);
        const parsed = JSON.parse(JSON.stringify(state));
        delete parsed.deadButton;
        delete parsed.deadSmallBlind;
        delete parsed.postedBlinds;

        const store = new Map([[HoldemState.STORAGE_KEY, JSON.stringify(parsed)]]);
        globalThis.localStorage = {
            getItem: key => (store.has(key) ? store.get(key) : null),
            setItem: (key, value) => store.set(key, value),
            removeItem: key => store.delete(key),
        };

        const loaded = HoldemState.load();
        assert.equal(loaded.deadButton, false);
        assert.equal(loaded.deadSmallBlind, false);
        assert.equal(loaded.postedBlinds, null);

        HoldemState.startNextHand(loaded);
        assert.ok(loaded.seats[loaded.dealerSeatIndex].inHand, "and rotates the ordinary way");
        delete globalThis.localStorage;
    });
});

describe("chips are not invented or lost by any of it", () => {
    test("posting one blind instead of two moves chips and doesn't make them", () => {
        // Measured across the deal, which is the step that touches stacks. A hand with
        // a dead small blind has one blind in the middle instead of two — the danger is
        // a null small blind being treated as a zero-cost posting somewhere, or the big
        // blind quietly covering for it.
        const state = table(1);
        const chips = s => s.seats.reduce(
            (sum, p) => sum + Betting.stackOf(s, p) + Betting.handTotal(p), 0);

        Betting.beginHand(state);
        leave(state, 3);                        // the big blind goes, small blind dies

        for (let hand = 0; hand < 4; hand++) {
            HoldemState.startNextHand(state);
            const before = chips(state);
            Betting.beginHand(state);
            assert.equal(chips(state), before, `the deal drifted the count on hand ${hand + 1}`);
        }
    });

    test("a dead small blind takes exactly one blind out of one stack", () => {
        const state = table(1);
        Betting.beginHand(state);
        leave(state, 3);
        HoldemState.startNextHand(state);

        const stacks = () => state.seats.map(p => Betting.stackOf(state, p));
        const before = stacks();
        Betting.beginHand(state);
        const after = stacks();

        const paid = before.map((v, i) => v - after[i]).filter(d => d !== 0);
        assert.deepEqual(paid, [state.bigBlind], "one player, one big blind, nobody else touched");
    });
});