Add a few good deterministic tests

frontend/deterministic-tests/src/tests/3-coalesce-update-remote-update-data-loss.test.ts

@@ -0,0 +1,49 @@
+import type { TestDefinition } from "../test-definition";
+
+export const coalesceUpdateRemoteUpdateDataLossTest: TestDefinition = {
+    name: "Local and remote edits to the same file are both preserved",
+    description:
+        "Client 0 edits a file while client 1 is offline. Client 1 reconnects " +
+        "and immediately edits the same file. Both edits should be preserved.",
+    clients: 2,
+    steps: [
+        {
+            type: "create",
+            client: 0,
+            path: "doc.md",
+            content: "line 1\nline 2\nline 3"
+        },
+        { type: "enable-sync", client: 0 },
+        { type: "enable-sync", client: 1 },
+        { type: "barrier" },
+
+        { type: "disable-sync", client: 1 },
+
+        {
+            type: "update",
+            client: 0,
+            path: "doc.md",
+            content: "line 1\nline 2\nline 3\nclient 0 addition"
+        },
+        { type: "sync", client: 0 },
+
+        {
+            type: "update",
+            client: 1,
+            path: "doc.md",
+            content: "client 1 addition\nline 1\nline 2\nline 3"
+        },
+
+        { type: "enable-sync", client: 1 },
+        { type: "barrier" },
+
+        {
+            type: "assert-consistent",
+            verify: (state) => {
+                state
+                    .assertFileCount(1)
+                    .assertContains("doc.md", "client 0 addition", "client 1 addition");
+            }
+        }
+    ]
+};