diff --git a/eslint.config.js b/eslint.config.js
index 0f337f7..8d43e46 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -22,7 +22,7 @@ export default tsEslint.config(
     },
   },
   {
-    files: ["**/*.spec.*"],
+    files: ["**/*.spec.*", "**/*.test.*"],
     rules: {
       // To make it easier to pass incorrect data to functions under test
       "@typescript-eslint/no-explicit-any": "off",
diff --git a/src/lib/solver.spec.ts b/src/lib/solver.spec.ts
index 87a6a83..78c8715 100644
--- a/src/lib/solver.spec.ts
+++ b/src/lib/solver.spec.ts
@@ -1,8 +1,7 @@
-import t from "tap";
+import t, { type Test } from "tap";
 
-import { ExpectedOutcome, FinalOutcome, Player } from "./datatypes.ts";
+import { CurrentOutcome, ExpectedOutcome, FinalOutcome, GameRules, Player, SquareState } from "./datatypes.ts";
 import { computeAllSolutions, getPreferredNextOutcome } from "./solver.ts";
-import { rules } from "./tictactoe-rules.ts";
 
 void t.test("getPreferredNextOutcome", async (t) => {
   const nextOutcomes: ExpectedOutcome[] = [
@@ -84,237 +83,359 @@ void t.test("getPreferredNextOutcome", async (t) => {
 });
 
 void t.test("computeAllSolutions", async (t) => {
+  // Simple rules: whoever occupies all the squares passed as a parameter, wins
+  const createRulesForSquares = (...squares: [number, number][]): GameRules => ({
+    getBoardOutcome: (board) => {
+      let hasX = false;
+      let hasO = false;
+      let hasUnoccupied = false;
+
+      for (const [row, column] of squares) {
+        const state = board.get(row, column);
+        switch (state) {
+          case SquareState.X:
+            hasX = true;
+            break;
+          case SquareState.O:
+            hasO = true;
+            break;
+          case SquareState.Unoccupied:
+            hasUnoccupied = true;
+            break;
+        }
+      }
+
+      if (hasX && hasO) {
+        return CurrentOutcome.Draw;
+      }
+
+      if (hasUnoccupied) {
+        return CurrentOutcome.Undecided;
+      }
+
+      if (hasX) {
+        return CurrentOutcome.WinX;
+      }
+
+      if (hasO) {
+        return CurrentOutcome.WinO;
+      }
+
+      // Special case: if there are no X, O or unoccupied squares,
+      // this means that the squares list is empty,
+      // and in this case we only want to decide the board as Draw when it's full
+      // and no moves can be made.
+      if (board.serialize().includes("_")) {
+        return CurrentOutcome.Undecided;
+      }
+
+      return CurrentOutcome.Draw;
+    },
+  });
+
   const checkSolutionsComplete = (
+    t: Test,
     rows: number,
     columns: number,
+    squares: [number, number][],
     expectedSolutions: Record<string, ExpectedOutcome>,
   ) => {
-    t.matchOnlyStrict(Object.fromEntries(computeAllSolutions(rows, columns, rules).entries()), expectedSolutions);
-  };
-
-  const checkSolutionsIncomplete = (
-    rows: number,
-    columns: number,
-    expectedSolutionsCount: number,
-    expectedSolutionsIncomplete: Record<string, ExpectedOutcome>,
-  ) => {
-    const allSolutions = computeAllSolutions(rows, columns, rules);
-    t.equal(allSolutions.size, expectedSolutionsCount);
-    t.matchStrict(Object.fromEntries(allSolutions.entries()), expectedSolutionsIncomplete);
+    const rules = createRulesForSquares(...squares);
+    const solutions = computeAllSolutions(rows, columns, rules);
+    t.matchOnlyStrict(Object.fromEntries(solutions.entries()), expectedSolutions);
   };
 
-  checkSolutionsComplete(0, 0, {
-    "": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+  void t.test("empty boards", async (t) => {
+    void t.test("0x0 board", async (t) => {
+      checkSolutionsComplete(t, 0, 0, [], {
+        "": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
+
+    void t.test("0x1 board", async (t) => {
+      checkSolutionsComplete(t, 0, 1, [], {
+        "": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
+
+    void t.test("0x2 board", async (t) => {
+      checkSolutionsComplete(t, 0, 2, [], {
+        "": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
+
+    void t.test("1x0 board", async (t) => {
+      checkSolutionsComplete(t, 1, 0, [], {
+        "": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
+
+    void t.test("2x0 board", async (t) => {
+      checkSolutionsComplete(t, 2, 0, [], {
+        "|": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
   });
 
-  checkSolutionsComplete(1, 0, {
-    "": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-  });
-
-  checkSolutionsComplete(1, 1, {
-    _: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    X: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+  void t.test("1x1 board", async (t) => {
+    void t.test("no winning squares", async (t) => {
+      checkSolutionsComplete(t, 1, 1, [], {
+        _: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        X: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
+
+    void t.test("one winning square", async (t) => {
+      checkSolutionsComplete(t, 1, 1, [[0, 0]], {
+        _: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+        X: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+      });
+    });
   });
 
   // making sure that we don't have any bugs that would manifest when width > height
-  checkSolutionsComplete(1, 3, {
-    ___: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-
-    X__: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    __X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-
-    XO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    X_O: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    OX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    _XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    O_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    _OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-
-    XOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    XXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    OXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+  void t.test("1x3 board", async (t) => {
+    void t.test("no winning squares", async (t) => {
+      checkSolutionsComplete(t, 1, 3, [], {
+        ___: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+
+        X__: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        _X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        __X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+        XO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        X_O: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        OX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        _XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        O_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        _OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+
+        XOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        XXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        OXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
+
+    void t.test("one winning square", async (t) => {
+      checkSolutionsComplete(t, 1, 3, [[0, 1]], {
+        ___: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+
+        X__: { finalOutcome: FinalOutcome.WinO, movesLeft: 1 },
+        _X_: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+        __X: { finalOutcome: FinalOutcome.WinO, movesLeft: 1 },
+
+        XO_: { finalOutcome: FinalOutcome.WinO, movesLeft: 0 },
+        X_O: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+        O_X: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+        _OX: { finalOutcome: FinalOutcome.WinO, movesLeft: 0 },
+
+        XXO: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+        OXX: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+      });
+    });
+
+    void t.test("two winning squares", async (t) => {
+      checkSolutionsComplete(
+        t,
+        1,
+        3,
+        [
+          [0, 0],
+          [0, 1],
+        ],
+        {
+          ___: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+
+          X__: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          _X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          __X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+          XO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          X_O: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+          OX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          _XO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+          O_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          _OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+
+          XOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          XXO: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+          OXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        },
+      );
+    });
   });
 
   // making sure that we don't have any bugs that would manifest when height > width
-  checkSolutionsComplete(3, 1, {
-    "_|_|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-
-    "X|_|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "_|X|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "_|_|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-
-    "X|O|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "X|_|O": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "O|X|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "_|X|O": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "O|_|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "_|O|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-
-    "X|O|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    "X|X|O": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    "O|X|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-  });
-
-  // smallest possible board where X can win
-  checkSolutionsComplete(1, 5, {
-    _____: { finalOutcome: FinalOutcome.Draw, movesLeft: 5 },
-
-    X____: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
-    XO___: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    X_O__: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    X__O_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    X___O: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    _X___: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
-    OX___: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    _XO__: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    _X_O_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    _X__O: { finalOutcome: FinalOutcome.WinX, movesLeft: 3 },
-    __X__: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
-    O_X__: { finalOutcome: FinalOutcome.WinX, movesLeft: 3 },
-    _OX__: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    __XO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    __X_O: { finalOutcome: FinalOutcome.WinX, movesLeft: 3 },
-    ___X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
-    O__X_: { finalOutcome: FinalOutcome.WinX, movesLeft: 3 },
-    _O_X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    __OX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    ___XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    ____X: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
-    O___X: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    _O__X: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    __O_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    ___OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-
-    XOX__: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    XO_X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    XO__X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    XXO__: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    X_OX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    X_O_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    XX_O_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    X_XO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    X__OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    XX__O: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    X_X_O: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    X__XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    OXX__: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    OX_X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    OX__X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _XOX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _XO_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _XXO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _X_OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _XX_O: { finalOutcome: FinalOutcome.WinX, movesLeft: 2 },
-    _X_XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    O_XX_: { finalOutcome: FinalOutcome.WinX, movesLeft: 2 },
-    O_X_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _OXX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _OX_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    __XOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    __XXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    O__XX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    _O_XX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    __OXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-
-    XOXO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    XOX_O: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    XOOX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    XO_XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    XOO_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    XO_OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    XXOO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    XXO_O: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    X_OXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    X_OOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    XX_OO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    X_XOO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    OXXO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    OXX_O: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    OXOX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    OX_XO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    OXO_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    OX_OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    _XOXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    _XOOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    _XXOO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    OOXX_: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    O_XXO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    OOX_X: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    O_XOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    _OXXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    _OXOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    OO_XX: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    O_OXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    _OOXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-
-    XOXOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    XOXXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    XOOXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    XXOOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    XXOXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    XXXOO: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
-    OXXOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    OXXXO: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
-    OXOXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    OOXXX: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
-  });
-
-  checkSolutionsComplete(2, 2, {
-    "__|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
-
-    "X_|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    "XO|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "X_|O_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "X_|_O": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-
-    "_X|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    "OX|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "_X|O_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "_X|_O": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-
-    "__|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    "O_|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "_O|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "__|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-
-    "__|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
-    "O_|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "_O|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-    "__|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
-
-    "XO|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "XO|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "XX|O_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "X_|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "XX|_O": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "X_|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "OX|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "OX|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "_X|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "_X|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "O_|XX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-    "_O|XX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
-
-    "XO|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    "XO|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    "XX|OO": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    "OX|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    "OX|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
-    "OO|XX": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+  void t.test("3x1 board", async (t) => {
+    void t.test("no winning squares", async (t) => {
+      checkSolutionsComplete(t, 3, 1, [], {
+        "_|_|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+
+        "X|_|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "_|X|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "_|_|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+        "X|O|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "X|_|O": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "O|X|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "_|X|O": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "O|_|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "_|O|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+
+        "X|O|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        "X|X|O": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        "O|X|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
+
+    void t.test("one winning square", async (t) => {
+      checkSolutionsComplete(t, 3, 1, [[1, 0]], {
+        "_|_|_": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+
+        "X|_|_": { finalOutcome: FinalOutcome.WinO, movesLeft: 1 },
+        "_|X|_": { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+        "_|_|X": { finalOutcome: FinalOutcome.WinO, movesLeft: 1 },
+
+        "X|O|_": { finalOutcome: FinalOutcome.WinO, movesLeft: 0 },
+        "X|_|O": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+        "O|_|X": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+        "_|O|X": { finalOutcome: FinalOutcome.WinO, movesLeft: 0 },
+
+        "X|X|O": { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+        "O|X|X": { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+      });
+    });
+
+    void t.test("two winning squares", async (t) => {
+      checkSolutionsComplete(
+        t,
+        3,
+        1,
+        [
+          [0, 0],
+          [1, 0],
+        ],
+        {
+          "_|_|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+
+          "X|_|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "_|X|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "_|_|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+          "X|O|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "X|_|O": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+          "O|X|_": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "_|X|O": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+          "O|_|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "_|O|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+
+          "X|O|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "X|X|O": { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+          "O|X|X": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        },
+      );
+    });
   });
 
-  // number 5478 taken from https://math.stackexchange.com/a/613505
-  checkSolutionsIncomplete(3, 3, 5478, {
-    "___|___|___": { finalOutcome: FinalOutcome.Draw, movesLeft: 9 },
-    "X__|___|___": { finalOutcome: FinalOutcome.Draw, movesLeft: 8 },
-    "_X_|___|___": { finalOutcome: FinalOutcome.Draw, movesLeft: 8 },
-    "___|_X_|___": { finalOutcome: FinalOutcome.Draw, movesLeft: 8 },
-    "XO_|___|___": { finalOutcome: FinalOutcome.WinX, movesLeft: 5 },
-    "X__|___|_O_": { finalOutcome: FinalOutcome.WinX, movesLeft: 5 },
-    "X_O|___|___": { finalOutcome: FinalOutcome.WinX, movesLeft: 5 },
-    "X__|___|__O": { finalOutcome: FinalOutcome.WinX, movesLeft: 5 },
-    "OO_|___|_XX": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
-    "OO_|__X|_XX": { finalOutcome: FinalOutcome.WinO, movesLeft: 1 },
+  void t.test("2x2 board", async (t) => {
+    void t.test("no winning squares", async (t) => {
+      checkSolutionsComplete(t, 2, 2, [], {
+        "__|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
+
+        "X_|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+        "XO|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "X_|O_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "X_|_O": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+        "_X|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+        "OX|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "_X|O_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "_X|_O": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+        "__|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+        "O_|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "_O|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "__|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+        "__|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+        "O_|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "_O|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+        "__|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+        "XO|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "XO|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "XX|O_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "X_|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "XX|_O": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "X_|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "OX|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "OX|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "_X|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "_X|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "O_|XX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+        "_O|XX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+
+        "XO|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        "XO|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        "XX|OO": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        "OX|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        "OX|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+        "OO|XX": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+      });
+    });
+
+    void t.test("two winning squares", async (t) => {
+      checkSolutionsComplete(
+        t,
+        2,
+        2,
+        [
+          [0, 0],
+          [0, 1],
+        ],
+        {
+          "__|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
+
+          "X_|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "XO|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "X_|O_": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+          "X_|_O": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+
+          "_X|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "OX|__": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "_X|O_": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+          "_X|_O": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+
+          "__|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+          "O_|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "_O|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "__|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+          "__|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+          "O_|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "_O|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "__|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+          "XO|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "XO|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "XX|O_": { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+          "X_|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "XX|_O": { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+          "X_|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "OX|X_": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "OX|_X": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "_X|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "_X|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+          "O_|XX": { finalOutcome: FinalOutcome.WinO, movesLeft: 1 },
+          "_O|XX": { finalOutcome: FinalOutcome.WinO, movesLeft: 1 },
+
+          "XO|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "XO|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "OX|XO": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "OX|OX": { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+          "OO|XX": { finalOutcome: FinalOutcome.WinO, movesLeft: 0 },
+        },
+      );
+    });
   });
 });
diff --git a/src/lib/tictactoe.test.ts b/src/lib/tictactoe.test.ts
new file mode 100644
index 0000000..6866347
--- /dev/null
+++ b/src/lib/tictactoe.test.ts
@@ -0,0 +1,144 @@
+import t from "tap";
+
+import { ExpectedOutcome, FinalOutcome } from "./datatypes.ts";
+import { computeAllSolutions } from "./solver.ts";
+import { rules } from "./tictactoe-rules.ts";
+
+void t.test("computeAllSolutions", async (t) => {
+  const checkSolutionsComplete = (
+    rows: number,
+    columns: number,
+    expectedSolutions: Record<string, ExpectedOutcome>,
+  ) => {
+    t.matchOnlyStrict(Object.fromEntries(computeAllSolutions(rows, columns, rules).entries()), expectedSolutions);
+  };
+
+  const checkSolutionsIncomplete = (
+    rows: number,
+    columns: number,
+    expectedSolutionsCount: number,
+    expectedSolutionsIncomplete: Record<string, ExpectedOutcome>,
+  ) => {
+    const allSolutions = computeAllSolutions(rows, columns, rules);
+    t.equal(allSolutions.size, expectedSolutionsCount);
+    t.matchStrict(Object.fromEntries(allSolutions.entries()), expectedSolutionsIncomplete);
+  };
+
+  // smallest possible board where X can win
+  checkSolutionsComplete(1, 5, {
+    _____: { finalOutcome: FinalOutcome.Draw, movesLeft: 5 },
+
+    X____: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
+    XO___: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    X_O__: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    X__O_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    X___O: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    _X___: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
+    OX___: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    _XO__: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    _X_O_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    _X__O: { finalOutcome: FinalOutcome.WinX, movesLeft: 3 },
+    __X__: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
+    O_X__: { finalOutcome: FinalOutcome.WinX, movesLeft: 3 },
+    _OX__: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    __XO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    __X_O: { finalOutcome: FinalOutcome.WinX, movesLeft: 3 },
+    ___X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
+    O__X_: { finalOutcome: FinalOutcome.WinX, movesLeft: 3 },
+    _O_X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    __OX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    ___XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    ____X: { finalOutcome: FinalOutcome.Draw, movesLeft: 4 },
+    O___X: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    _O__X: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    __O_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+    ___OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 3 },
+
+    XOX__: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    XO_X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    XO__X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    XXO__: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    X_OX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    X_O_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    XX_O_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    X_XO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    X__OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    XX__O: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    X_X_O: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    X__XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    OXX__: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    OX_X_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    OX__X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    _XOX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    _XO_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    _XXO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    _X_OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    _XX_O: { finalOutcome: FinalOutcome.WinX, movesLeft: 2 },
+    _X_XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    O_XX_: { finalOutcome: FinalOutcome.WinX, movesLeft: 2 },
+    O_X_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    _OXX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    _OX_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    __XOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    __XXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    O__XX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    _O_XX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+    __OXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 2 },
+
+    XOXO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    XOX_O: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    XOOX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    XO_XO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    XOO_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    XO_OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    XXOO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    XXO_O: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    X_OXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    X_OOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    XX_OO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    X_XOO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    OXXO_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    OXX_O: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    OXOX_: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    OX_XO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    OXO_X: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    OX_OX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    _XOXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    _XOOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    _XXOO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    OOXX_: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    O_XXO: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    OOX_X: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    O_XOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    _OXXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    _OXOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    OO_XX: { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    O_OXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+    _OOXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 1 },
+
+    XOXOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+    XOXXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+    XOOXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+    XXOOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+    XXOXO: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+    XXXOO: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+    OXXOX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+    OXXXO: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+    OXOXX: { finalOutcome: FinalOutcome.Draw, movesLeft: 0 },
+    OOXXX: { finalOutcome: FinalOutcome.WinX, movesLeft: 0 },
+  });
+
+  // number 5478 taken from https://math.stackexchange.com/a/613505
+  checkSolutionsIncomplete(3, 3, 5478, {
+    "___|___|___": { finalOutcome: FinalOutcome.Draw, movesLeft: 9 },
+    "X__|___|___": { finalOutcome: FinalOutcome.Draw, movesLeft: 8 },
+    "_X_|___|___": { finalOutcome: FinalOutcome.Draw, movesLeft: 8 },
+    "___|_X_|___": { finalOutcome: FinalOutcome.Draw, movesLeft: 8 },
+    "XO_|___|___": { finalOutcome: FinalOutcome.WinX, movesLeft: 5 },
+    "X__|___|_O_": { finalOutcome: FinalOutcome.WinX, movesLeft: 5 },
+    "X_O|___|___": { finalOutcome: FinalOutcome.WinX, movesLeft: 5 },
+    "X__|___|__O": { finalOutcome: FinalOutcome.WinX, movesLeft: 5 },
+    "OO_|___|_XX": { finalOutcome: FinalOutcome.WinX, movesLeft: 1 },
+    "OO_|__X|_XX": { finalOutcome: FinalOutcome.WinO, movesLeft: 1 },
+  });
+});