add retry logic to the analyze test (#313)

I have been noticing a bunch of flakes on this test due to a race condition of the analyzer picking up the new files and us asking for errors.

This allows us to retry with a back off until we see the error show up, allowing the test to pass quickly after the error does appear.

Author: jakemac53

pkgs/dart_mcp_server/test/test_harness.dart

@@ -26,6 +26,21 @@ import 'package:test/test.dart';
 import 'package:test_process/test_process.dart';
 import 'package:unified_analytics/unified_analytics.dart';
 
+Future<T> callWithRetry<T>(
+  FutureOr<T> Function() fn, {
+  int maxTries = 5,
+}) async {
+  var tryCount = 0;
+  while (true) {
+    try {
+      return await fn();
+    } catch (_) {
+      if (tryCount++ >= maxTries) rethrow;
+    }
+    await Future<void>.delayed(Duration(milliseconds: 100 * tryCount));
+  }
+}
+
 /// A full environment for integration testing the MCP server.
 ///
 /// - Runs the counter app at `test_fixtures/counter_app` using `flutter run`.
@@ -187,17 +202,10 @@ class TestHarness {
     CallToolRequest request, {
     int maxTries = 5,
     bool expectError = false,
-  }) async {
-    var tryCount = 0;
-    while (true) {
-      try {
-        return await callTool(request, expectError: expectError);
-      } catch (_) {
-        if (tryCount++ >= maxTries) rethrow;
-      }
-      await Future<void>.delayed(Duration(milliseconds: 100 * tryCount));
-    }
-  }
+  }) => callWithRetry(
+    () => callTool(request, expectError: expectError),
+    maxTries: maxTries,
+  );
 
   /// Calls [getPrompt] on the [mcpServerConnection].
   Future<GetPromptResult> getPrompt(GetPromptRequest request) =>

pkgs/dart_mcp_server/test/tools/analyzer_test.dart

@@ -309,27 +309,30 @@ void main() {
           ],
         },
       );
-      final result = await testHarness.callToolWithRetry(request, maxTries: 10);
-      expect(result.isError, isNot(true));
-      expect(result.content, hasLength(2));
-      expect(
-        result.content,
-        containsAll([
-          isA<TextContent>().having(
-            (t) => t.text,
-            'text',
-            contains(
-              "The argument type 'String' can't be assigned to the "
-              "parameter type 'num'.",
+      // It may take a bit for the errors to show up.
+      await callWithRetry(() async {
+        final result = await testHarness.callTool(request);
+        expect(result.isError, isNot(true));
+        expect(result.content, hasLength(2));
+        expect(
+          result.content,
+          containsAll([
+            isA<TextContent>().having(
+              (t) => t.text,
+              'text',
+              contains(
+                "The argument type 'String' can't be assigned to the "
+                "parameter type 'num'.",
+              ),
             ),
-          ),
-          isA<TextContent>().having(
-            (t) => t.text,
-            'text',
-            contains("Undefined name 'foo'"),
-          ),
-        ]),
-      );
+            isA<TextContent>().having(
+              (t) => t.text,
+              'text',
+              contains("Undefined name 'foo'"),
+            ),
+          ]),
+        );
+      }, maxTries: 10);
     });
 
     test('can look up symbols in a workspace', () async {