works

frontend/test-client/src/agent/mock-agent.ts

@@ -83,8 +83,6 @@ export class MockAgent extends MockClient {
 	}
 
 	public async act(): Promise<void> {
-		this.assertAllContentIsPresentOnce();
-
 		const options: (() => Promise<unknown>)[] = [
 			this.createFileAction.bind(this),
 			this.changeFetchChangesUpdateIntervalMsAction.bind(this)

frontend/test-client/src/agent/mock-client.ts

@@ -1,3 +1,4 @@
+import { assert } from "../utils/assert";
 import type {
 	RelativePath,
 	FileSystemOperations,
@@ -81,6 +82,18 @@ export class MockClient implements FileSystemOperations {
 		const newContentUint8Array = new TextEncoder().encode(newContent);
 		this.localFiles.set(path, newContentUint8Array);
 
+		const existingPats = currentContent
+			.split(" ")
+			.map((part) => part.trim());
+		const newParts = newContent.split(" ").map((part) => part.trim());
+		existingPats.forEach((part) =>
+			// all changes should be additive
+			assert(
+				newParts.includes(part),
+				`Part ${part} not found in new content`
+			)
+		);
+
 		this.client.logger.info(
 			`Updated file ${path} with:\n  current content: ${currentContent}\n  new content: ${newContent}`
 		);