Commit LLM generated test cases

frontend/deterministic-tests/src/tests/overlapping-edits-same-section.test.ts

@@ -0,0 +1,86 @@
+import type { ClientState, TestDefinition } from "../test-definition";
+import { assert } from "../utils/assert";
+
+function verifyMergedEdits(state: ClientState): void {
+    assert(
+        state.files.size === 1,
+        `Expected 1 file, got ${state.files.size}`
+    );
+    assert(
+        state.files.has("doc.md"),
+        `Expected doc.md to exist`
+    );
+    const content = state.files.get("doc.md") ?? "";
+
+    // Both edits should be present in the merged result.
+    // Client 0 added "alpha addition" and Client 1 added "beta addition".
+    // The shared heading and footer should be preserved.
+    assert(
+        content.includes("# Title"),
+        `Expected "# Title" to be preserved, got: "${content}"`
+    );
+    assert(
+        content.includes("alpha addition"),
+        `Expected Client 0's edit "alpha addition" to be present, got: "${content}"`
+    );
+    assert(
+        content.includes("beta addition"),
+        `Expected Client 1's edit "beta addition" to be present, got: "${content}"`
+    );
+    assert(
+        content.includes("footer"),
+        `Expected "footer" to be preserved, got: "${content}"`
+    );
+}
+
+export const overlappingEditsSameSectionTest: TestDefinition = {
+    name: "Overlapping Edits in Same Section",
+    description:
+        "Both clients edit the same document by adding content to different " +
+        "parts of the same section. Client 0 adds a line after the heading, " +
+        "Client 1 adds a line before the footer. The 3-way merge should " +
+        "preserve both edits without data loss.",
+    clients: 2,
+    steps: [
+        // Setup: create a multi-line document
+        {
+            type: "create",
+            client: 0,
+            path: "doc.md",
+            content: "# Title\n\nfooter"
+        },
+        { type: "enable-sync", client: 0 },
+        { type: "enable-sync", client: 1 },
+        { type: "sync" },
+        { type: "barrier" },
+
+        // Both clients go offline and edit the same document
+        { type: "disable-sync", client: 0 },
+        { type: "disable-sync", client: 1 },
+
+        // Client 0: add line after heading
+        {
+            type: "update",
+            client: 0,
+            path: "doc.md",
+            content: "# Title\nalpha addition\n\nfooter"
+        },
+
+        // Client 1: add line before footer
+        {
+            type: "update",
+            client: 1,
+            path: "doc.md",
+            content: "# Title\n\nbeta addition\nfooter"
+        },
+
+        // Both reconnect
+        { type: "enable-sync", client: 0 },
+        { type: "enable-sync", client: 1 },
+        { type: "sync" },
+        { type: "barrier" },
+
+        // Both edits should be merged
+        { type: "assert-consistent", verify: verifyMergedEdits }
+    ]
+};