Illusion walls shimmer until YOU test them (rules rev 29)

Per the owner's design — and truer to a real table, where the cast is
public: every illusion wall's location is open knowledge, rendered as a
shimmering wall to any player whose eyes have not yet ruled on it.
Testing is an explicit act: tap the shimmer (or bump into it) and a
modal explains the 50/50 and offers 'Roll to test your eyes' — the new
testIllusion command rolls once, then the wall either hardens or
dissolves for you alone. Nobody's verdict is moved by watching someone
else stroll through (the Q3WZ mystery: an automaton walking through
its own round-1 fake). Untested walls block movement and sight without
consuming RNG; the pre-29 lazy belief roll is preserved for stored
games. Automatons doubt free shimmers on their best crossing before
spending any card on that wall.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0138A8CjeQRpvzKxuMfz1Bqc

packages/engine/test/sight-illusions-sectors.test.ts

@@ -500,3 +500,61 @@ describe("sight tracing", () => {
     expect(warped).toBeGreaterThan(0);
   });
 });
+
+describe("illusions are tested by choice (rules rev 29)", () => {
+  function shimmerRig() {
+    let { state } = createGame({ playerIds: ["a", "b"], seed: 42, sets: ["basic"], deckRev: 29 });
+    state = toRound2(state);
+    const caster = activePlayer(state);
+    const mark = state.players.find((p) => p.id !== caster.id)!;
+    // Conjure the illusion on an OPEN edge beside the victim (state surgery
+    // for a deterministic spot; the cast itself is tested elsewhere).
+    const spot = emptyNeighborCell(state, mark.position);
+    const key = edgeKey(mark.position, spot.side);
+    state.illusionWalls[key] = { createdBy: caster.id, belief: {} };
+    state = must(state, caster.id, { type: "endTurn", draw: 0 });
+    return {
+      state, caster: caster.id, victim: mark.id, side: spot.side,
+      cell: { ...state.players.find((p) => p.id === mark.id)!.position },
+    };
+  }
+
+  it("an untested shimmer blocks the walker with its own message, no die rolled", () => {
+    const { state, victim, side } = shimmerRig();
+    const rngBefore = JSON.stringify(state.rng);
+    const r = applyCommand(state, victim, { type: "move", direction: side });
+    expect(r.ok).toBe(false);
+    if (!r.ok) expect(r.error).toContain("shimmers");
+    expect(JSON.stringify(state.rng)).toBe(rngBefore);
+  });
+
+  it("the belief test is an explicit roll; the verdict then governs the wall", () => {
+    let { state, victim, cell, side } = shimmerRig();
+    state = must(state, victim, { type: "testIllusion", cell, side });
+    const verdict = state.illusionWalls[edgeKey(cell, side)]!.belief[victim];
+    expect(verdict === "believes" || verdict === "seesThrough").toBe(true);
+    const r = applyCommand(state, victim, { type: "move", direction: side });
+    if (verdict === "seesThrough") {
+      expect(r.ok).toBe(true);
+    } else {
+      expect(r.ok).toBe(false);
+      if (!r.ok) expect(r.error).toBe("blocked by wall");
+    }
+    // A second test is refused: eyes rule once.
+    expect(applyCommand(state, victim, { type: "testIllusion", cell, side }).ok).toBe(false);
+  });
+
+  it("the creator strolls through their own fake without any test", () => {
+    let { state, caster } = shimmerRig();
+    // Skip to the caster's turn; the wall never blocks its maker.
+    while (activePlayer(state).id !== caster) {
+      state = must(state, activePlayer(state).id, { type: "endTurn", draw: 0 });
+    }
+    const me = state.players.find((p) => p.id === caster)!;
+    const other = state.players.find((p) => p.id !== caster)!;
+    me.position = { ...other.position };
+    const r = applyCommand(state, caster, { type: "move", direction: "E" });
+    // Blocked only if some REAL edge stands there; the illusion itself never objects.
+    if (!r.ok) expect(r.error).not.toContain("shimmers");
+  });
+});