Convert tests to use RuleTester instead of --report-unused-disable-di…

…rectives

The RuleTester provides the ability to assert on specific error messages and fixes that rules produce. It's also more in line with how the upstream projects (eslint and typescript-eslint) test their rules, which will smooth the process if we decide to upstream these rules.

The tests for (and changes to) no-meaningless-void-operator are changes I made based on feedback on my typescript-eslint PR: typescript-eslint/typescript-eslint#3641

.eslintrc.js

@@ -4,4 +4,12 @@ module.exports = {
   parserOptions: {
     project: "tsconfig.json",
   },
+
+  overrides: [
+    {
+      files: ["*.ts", "*.tsx"],
+      extends: ["plugin:@foxglove/typescript"],
+      parserOptions: { project: "tsconfig.json" },
+    },
+  ],
 };

configs/typescript.test.ts → configs/typescript.example.ts

@@ -1,5 +1,6 @@
 // Use --report-unused-disable-directives to validate errors
 
+/* eslint-disable no-unused-expressions */
 /* eslint-disable @typescript-eslint/no-unused-expressions */
 
 void (async () => {

jest.config.js

@@ -0,0 +1,4 @@
+module.exports = {
+  preset: "ts-jest",
+  testMatch: ["<rootDir>/**/*.test.ts"],
+};