Hi, I have a question about this issue. Is there any current way without the changes that will be made for this issue to test a flat config custom typescript-eslint rule? At the moment when using RuleTester from @typescript-eslint/rule-tester v7.11.0 I get the error:

FAIL  tests/rules/no-discard-result.test.ts [ tests/rules/no-discard-result.test.ts ]
Error: This method cannot be used with flat config. Add your entries directly into the config array.
 ❯ assertEslintrcConfig ../../node_modules/eslint/lib/linter/linter.js:1256:15
 ❯ Linter.defineRule ../../node_modules/eslint/lib/linter/linter.js:2164:9
 ❯ RuleTester.run ../../node_modules/@typescript-eslint/rule-tester/src/RuleTester.ts:400:18
 ❯ tests/rules/no-discard-result.test.ts:15:13
     13| 
     14| describe('ESLint plugin result', () => {
     15|  ruleTester.run('no-discard-result', noDiscardResult, {
       |             ^
     16|   valid: [
     17|    {

This is for https://github.com/sapphiredev/utilities/blob/feat/update-to-eslint-v9-flat-config/packages/eslint-plugin-result/tests/rules/no-discard-result.test.ts

Nope! The way they designed the rule tester it is one or the other. Hence there is two rule tester classes. Our fork came from the legacy config version (before flat config existed) so it doesn't support flat config properties.

But regardless - the only difference is a few property names. The functionality is all the same.

Turns out if I update to the v8 rc then my tests work again so I'll just patiently wait for the typescript-eslint team to finish their work. Looking forward to it, keep up the awesome work!

The same problem:

Error: This method cannot be used with flat config. Add your entries directly into the config array.

Closed by #9603.