Add deterministic-tests (#190)

Reviewed-on: https://home.schmelczer.dev/git/git/andras/vault-link/pulls/190
Co-authored-by: Andras Schmelczer <andras@schmelczer.dev>
Co-committed-by: Andras Schmelczer <andras@schmelczer.dev>

frontend/deterministic-tests/src/tests/concurrent-edit-exact-same-position.test.ts

@@ -0,0 +1,49 @@
+import type { AssertableState } from "../utils/assertable-state";
+import type { TestDefinition } from "../test-definition";
+
+export const concurrentEditExactSamePositionTest: TestDefinition = {
+    description:
+        "Both clients replace the same word in a file with different text " +
+        "while offline. After syncing, the merged result should contain " +
+        "both replacements.",
+    clients: 2,
+    steps: [
+        {
+            type: "create",
+            client: 0,
+            path: "doc.md",
+            content: "the quick brown fox"
+        },
+        { type: "enable-sync", client: 0 },
+        { type: "enable-sync", client: 1 },
+        { type: "barrier" },
+
+        { type: "disable-sync", client: 0 },
+        { type: "disable-sync", client: 1 },
+        {
+            type: "update",
+            client: 0,
+            path: "doc.md",
+            content: "the slow brown fox"
+        },
+        {
+            type: "update",
+            client: 1,
+            path: "doc.md",
+            content: "the fast brown fox"
+        },
+
+        { type: "enable-sync", client: 0 },
+        { type: "enable-sync", client: 1 },
+        { type: "barrier" },
+
+        {
+            type: "assert-consistent",
+            verify: (state: AssertableState): void => {
+                state
+                    .assertFileCount(1)
+                    .assertContains("doc.md", "slow", "fast", "brown fox");
+            }
+        }
+    ]
+};