Initial Commit

packages/foundation/flow/undo/tests/properties/compress.prop.test.ts

@@ -0,0 +1,45 @@
+import { describe, it } from "@suaveplan/testing/runner";
+import * as fc from "fast-check";
+import { createCommand } from "../../src/command/command.js";
+import { compressHistory } from "../../src/compression/history-compressor.js";
+import { UndoStack } from "../../src/stack/stack.js";
+
+interface Counter {
+    value: number;
+}
+
+describe("property: compressHistory idempotency", () => {
+    it("re-compressing does not change state or exceed original size", {
+        timeout: 30000,
+    }, () => {
+        fc.assert(
+            fc.property(
+                fc.integer({ min: 0, max: 50 }),
+                fc.integer({ min: 1, max: 20 }),
+                (pushCount, depth) => {
+                    const s = new UndoStack<Counter>({ value: 0 });
+                    for (let i = 0; i < pushCount; i++) {
+                        s.push(
+                            createCommand(
+                                "Inc",
+                                (st) => ({ value: st.value + 1 }),
+                                (st) => ({ value: st.value - 1 })
+                            )
+                        );
+                    }
+                    const r1 = compressHistory(s, { compressionDepth: depth });
+                    const r2 = compressHistory(r1.stack, {
+                        compressionDepth: depth,
+                    });
+                    // State preserved
+                    if (r1.stack.current.value !== r2.stack.current.value)
+                        return false;
+                    // Second compression adds no new squashes (all same-label entries already merged)
+                    // Size should not increase
+                    return r2.newSize <= r1.newSize;
+                }
+            ),
+            { numRuns: 200 }
+        );
+    });
+});