Add Agent Eval assertions on files

Author: samedson

scripts/agent-evals/package-lock.json

@@ -11,8 +11,11 @@
   "author": "",
   "license": "ISC",
   "devDependencies": {
+    "@types/chai": "^4.3.0",
+    "@types/chai-fs": "^2.0.5",
     "@types/mocha": "^9.0.0",
-    "@types/node": "^24.9.0"
+    "@types/node": "^24.9.0",
+    "chai-fs": "^2.0.0"
   },
   "dependencies": {
     "mocha": "^11.7.1",

scripts/agent-evals/package.json

@@ -1,4 +1,5 @@
 import { ToolDef } from "./tool-matcher.js";
+import {Assertion} from "chai";
 
 export interface AgentTestRunner {
   /**
@@ -19,4 +20,10 @@ export interface AgentTestRunner {
    * an event is not found
    */
   expectToolCalls(tools: ToolDef[]): Promise<void>;
+
+  /**
+   * Returns an assertion object for the path inside the run directory that can
+   * be asserted on via chai-fs's API: https://www.chaijs.com/plugins/chai-fs/
+   */
+  expectFs(filePath: string): Chai.Assertion;
 }