From 160a5040f951f582eeae44f2102b1104eeba9183 Mon Sep 17 00:00:00 2001
From: mizdra <pp.mizdra@gmail.com>
Date: Wed, 25 Sep 2024 20:36:21 +0900
Subject: [PATCH 1/7] add test cases for 3rd-party plugin

---
 src/__snapshots__/core.test.ts.snap | 61 +++++++++++++++++++++--------
 src/core.test.ts                    | 37 +++++++++++++++++
 2 files changed, 81 insertions(+), 17 deletions(-)

diff --git a/src/__snapshots__/core.test.ts.snap b/src/__snapshots__/core.test.ts.snap
index bf9da771..4444aa26 100644
--- a/src/__snapshots__/core.test.ts.snap
+++ b/src/__snapshots__/core.test.ts.snap
@@ -69,6 +69,20 @@ exports[`Core > disablePerLine 1`] = `
 let a = 1;"
 `;
 
+exports[`Core > fixes problems with legacy config and 3rd-party plugins 1`] = `
+"// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+// eslint-disable-next-line test/ban-nullish-coalescing-operator
+2 ?? 2;"
+`;
+
 exports[`Core > flat config 1`] = `
 [
   {
@@ -194,6 +208,17 @@ exports[`Core > lint > returns lint results 1`] = `
     ],
     "warningCount": 0,
   },
+  {
+    "errorCount": 1,
+    "filePath": "<fixture>/src/ban-nullish-coalescing-operator.js",
+    "messages": [
+      {
+        "ruleId": "test/ban-nullish-coalescing-operator",
+        "severity": 2,
+      },
+    ],
+    "warningCount": 0,
+  },
   {
     "errorCount": 1,
     "filePath": "<fixture>/src/import-order.js",
@@ -270,22 +295,24 @@ exports[`Core > printDetailsOfResults 1`] = `
 `;
 
 exports[`Core > printSummaryOfResults 1`] = `
-"- 7 files (0 file passed, 7 files failed) checked.
-- 18 problems (17 errors, 1 warning) found.
-╔═════════════════════════════╤═══════╤═════════╤════════════╤═════════════════╗
-║ Rule                        │ Error │ Warning │ is fixable │ has suggestions ║
-╟─────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
-║ arrow-body-style            │ 12    │ 0       │ 12         │ 0               ║
-╟─────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
-║ ban-exponentiation-operator │ 1     │ 0       │ 0          │ 0               ║
-╟─────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
-║ import/order                │ 1     │ 0       │ 0          │ 0               ║
-╟─────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
-║ no-unsafe-negation          │ 1     │ 0       │ 0          │ 1               ║
-╟─────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
-║ no-unused-vars              │ 1     │ 0       │ 0          │ 0               ║
-╟─────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
-║ ]8;;https://example.comprefer-const]8;;                │ 1     │ 1       │ 2          │ 0               ║
-╚═════════════════════════════╧═══════╧═════════╧════════════╧═════════════════╝
+"- 8 files (0 file passed, 8 files failed) checked.
+- 19 problems (18 errors, 1 warning) found.
+╔══════════════════════════════════════╤═══════╤═════════╤════════════╤═════════════════╗
+║ Rule                                 │ Error │ Warning │ is fixable │ has suggestions ║
+╟──────────────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
+║ arrow-body-style                     │ 12    │ 0       │ 12         │ 0               ║
+╟──────────────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
+║ ban-exponentiation-operator          │ 1     │ 0       │ 0          │ 0               ║
+╟──────────────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
+║ test/ban-nullish-coalescing-operator │ 1     │ 0       │ 0          │ 0               ║
+╟──────────────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
+║ import/order                         │ 1     │ 0       │ 0          │ 0               ║
+╟──────────────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
+║ no-unsafe-negation                   │ 1     │ 0       │ 0          │ 1               ║
+╟──────────────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
+║ no-unused-vars                       │ 1     │ 0       │ 0          │ 0               ║
+╟──────────────────────────────────────┼───────┼─────────┼────────────┼─────────────────╢
+║ ]8;;https://example.comprefer-const]8;;                         │ 1     │ 1       │ 2          │ 0               ║
+╚══════════════════════════════════════╧═══════╧═════════╧════════════╧═════════════════╝
 "
 `;
diff --git a/src/core.test.ts b/src/core.test.ts
index 314965af..7e03cedf 100644
--- a/src/core.test.ts
+++ b/src/core.test.ts
@@ -82,6 +82,9 @@ const iff = await createIFF({
   'src/ban-exponentiation-operator.js': dedent`
     2 ** 2;
   `,
+  'src/ban-nullish-coalescing-operator.js': dedent`
+    2 ?? 2;
+  `,
   'src/no-unused-vars.js': dedent`
     const a = 1;
   `,
@@ -91,6 +94,33 @@ const iff = await createIFF({
   'src/no-unsafe-negation.js': dedent`
     if (!key in object) {}
   `,
+  'node_modules/eslint-plugin-test/package.json': dedent`
+    {
+      "name": "eslint-plugin-test",
+      "version": "1.0.0",
+      "main": "index.js"
+    }
+  `,
+  'node_modules/eslint-plugin-test/index.js': dedent`
+    module.exports = {
+      rules: {
+        'ban-nullish-coalescing-operator': {
+          create(context) {
+            return {
+              LogicalExpression: (node) => {
+                if (node.operator === '??') {
+                  context.report({
+                    node,
+                    message: 'Ban nullish coalescing operator',
+                  });
+                }
+              },
+            };
+          },
+        },
+      },
+    };
+  `,
   '.eslintrc.js': dedent`
     module.exports = {
       root: true,
@@ -98,11 +128,13 @@ const iff = await createIFF({
         ecmaVersion: 2021,
         sourceType: 'module',
       },
+      plugins: ['test'],
       overrides: [
         { files: ['prefer-const.js'], rules: { 'prefer-const': 'error' } },
         { files: ['arrow-body-style.js'], rules: { 'arrow-body-style': ['error', 'always'] } },
         { files: ['import-order.js'], rules: { 'import/order': 'error' } },
         { files: ['ban-exponentiation-operator.js'], rules: { 'ban-exponentiation-operator': 'error' } },
+        { files: ['ban-nullish-coalescing-operator.js'], rules: { 'test/ban-nullish-coalescing-operator': 'error' } },
         {
           files: ['no-unused-vars.js'],
           rules: { 'no-unused-vars': ['error', { varsIgnorePattern: '^_' }] },
@@ -312,4 +344,9 @@ describe('Core', () => {
     expect(await readFile(iff.paths['src/index.jsx'], 'utf-8')).toMatchSnapshot();
     expect(await readFile(iff.paths['src/.index.js'], 'utf-8')).toMatchSnapshot();
   });
+  test('fixes problems with legacy config and 3rd-party plugins', async () => {
+    const results = await core.lint();
+    await core.disablePerLine(results, ['test/ban-nullish-coalescing-operator']);
+    expect(await readFile(iff.paths['src/ban-nullish-coalescing-operator.js'], 'utf-8')).toMatchSnapshot();
+  });
 });

From 33de5de58245f03f45ffcc1cb59d5c3c5450be23 Mon Sep 17 00:00:00 2001
From: mizdra <pp.mizdra@gmail.com>
Date: Wed, 25 Sep 2024 20:37:34 +0900
Subject: [PATCH 2/7] logging for debug

---
 src/eslint/linter.ts | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/eslint/linter.ts b/src/eslint/linter.ts
index 8677ead0..06b4d1fd 100644
--- a/src/eslint/linter.ts
+++ b/src/eslint/linter.ts
@@ -49,9 +49,9 @@ export function verifyAndFix(
   do {
     passNumber++;
 
-    const messages = linter
-      .verify(currentText, config, filePath)
-      .filter((message) => message.ruleId && ruleIds.includes(message.ruleId));
+    const unfilteredMessages = linter.verify(currentText, config, filePath);
+    if (passNumber === 1) console.log('unfilteredMessages', unfilteredMessages);
+    const messages = unfilteredMessages.filter((message) => message.ruleId && ruleIds.includes(message.ruleId));
     const sourceCode = linter.getSourceCode();
 
     // Create `Rule.Fix[]`

From 0434b64787de1406fe333fd3cd7d5df3d97ac9ee Mon Sep 17 00:00:00 2001
From: mizdra <pp.mizdra@gmail.com>
Date: Wed, 25 Sep 2024 21:42:30 +0900
Subject: [PATCH 3/7] Revert "logging for debug"

This reverts commit 33de5de58245f03f45ffcc1cb59d5c3c5450be23.
---
 src/eslint/linter.ts | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/eslint/linter.ts b/src/eslint/linter.ts
index 06b4d1fd..8677ead0 100644
--- a/src/eslint/linter.ts
+++ b/src/eslint/linter.ts
@@ -49,9 +49,9 @@ export function verifyAndFix(
   do {
     passNumber++;
 
-    const unfilteredMessages = linter.verify(currentText, config, filePath);
-    if (passNumber === 1) console.log('unfilteredMessages', unfilteredMessages);
-    const messages = unfilteredMessages.filter((message) => message.ruleId && ruleIds.includes(message.ruleId));
+    const messages = linter
+      .verify(currentText, config, filePath)
+      .filter((message) => message.ruleId && ruleIds.includes(message.ruleId));
     const sourceCode = linter.getSourceCode();
 
     // Create `Rule.Fix[]`

From 0df8753f75f7b24ac299aec01b8e53fde9878cd0 Mon Sep 17 00:00:00 2001
From: mizdra <pp.mizdra@gmail.com>
Date: Wed, 25 Sep 2024 21:48:18 +0900
Subject: [PATCH 4/7] use `ESLint` instead of `Linter` to fix the code

---
 src/config.ts        |  2 ++
 src/core.ts          | 30 +++++++++++-------------------
 src/eslint/linter.ts | 18 ++++++++++--------
 3 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/src/config.ts b/src/config.ts
index 7dea6406..8abf8878 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -13,6 +13,7 @@ type LegacyESLintOptions = { type: 'eslintrc' } & Pick<
   | 'overrideConfig'
   | 'cwd'
   | 'resolvePluginsRelativeTo'
+  | 'plugins'
 >;
 type FlatESLintOptions = { type: 'flat' } & Pick<
   FlatESLint.Options,
@@ -110,6 +111,7 @@ export function normalizeConfig(config: Config): NormalizedConfig {
       cwd,
       resolvePluginsRelativeTo:
         config.eslintOptions.resolvePluginsRelativeTo ?? configDefaults.eslintOptions.resolvePluginsRelativeTo,
+      plugins: config.eslintOptions.plugins,
     };
   } else {
     eslintOptions = {
diff --git a/src/core.ts b/src/core.ts
index 85010558..2c5e7da9 100644
--- a/src/core.ts
+++ b/src/core.ts
@@ -1,6 +1,6 @@
 import { writeFile } from 'node:fs/promises';
 import { fileURLToPath } from 'node:url';
-import { ESLint, Linter, Rule } from 'eslint';
+import { ESLint, Rule } from 'eslint';
 import eslintPkg, { LegacyESLint as LegacyESLintNS } from 'eslint/use-at-your-own-risk';
 import isInstalledGlobally from 'is-installed-globally';
 import { DescriptionPosition } from './cli/prompt.js';
@@ -49,7 +49,14 @@ export class Core {
     const eslintOptions = this.config.eslintOptions;
     if (eslintOptions.type === 'eslintrc') {
       const { type, ...rest } = eslintOptions;
-      this.eslint = new LegacyESLint(rest);
+      this.eslint = new LegacyESLint({
+        ...rest,
+        plugins: {},
+        overrideConfig: {
+          ...rest.overrideConfig,
+          plugins: [...(rest.overrideConfig?.plugins ?? []), 'eslint-plugin-eslint-interactive'],
+        },
+      });
     } else {
       const { type, ...rest } = eslintOptions;
       this.eslint = new FlatESLint(rest);
@@ -191,20 +198,13 @@ export class Core {
   ): Promise<Undo> {
     // NOTE: Extract only necessary results and files for performance
     const filteredResultsOfLint = filterResultsByRuleId(resultsOfLint, ruleIds);
-    const linter = new Linter({ configType: this.config.eslintOptions.type });
 
     // eslint-disable-next-line prefer-const
     for (let { filePath, source } of filteredResultsOfLint) {
       if (!source) throw new Error('Source code is required to apply fixes.');
-      const config: Linter.Config | Linter.FlatConfig[] =
-        this.config.eslintOptions.type === 'eslintrc'
-          ? // eslint-disable-next-line no-await-in-loop
-            await this.eslint.calculateConfigForFile(filePath)
-          : // NOTE: For some reason, if files is not specified, it will not match .jsx
-            // eslint-disable-next-line no-await-in-loop
-            [{ ...(await calculateConfigForFile(this.eslint, filePath)), files: ['**/*.*', '**/*'] }];
 
-      const fixedResult = verifyAndFix(linter, source, config, filePath, ruleIds, fixCreator);
+      // eslint-disable-next-line no-await-in-loop
+      const fixedResult = await verifyAndFix(this.eslint, source, filePath, ruleIds, fixCreator);
 
       // Write the fixed source code to the file
       if (fixedResult.fixed) {
@@ -219,11 +219,3 @@ export class Core {
     };
   }
 }
-
-async function calculateConfigForFile(eslint: ESLint, filePath: string): Promise<Linter.FlatConfig> {
-  const config = await eslint.calculateConfigForFile(filePath);
-  // `language` property has been added to the object returned by `ESLint.prototype.calculateConfigForFile(filePath)` since ESLint v9.5.0.
-  // But, `Linter.prototype.verify()` does not accept `language` option. So, remove it.
-  delete config['language'];
-  return config;
-}
diff --git a/src/eslint/linter.ts b/src/eslint/linter.ts
index 8677ead0..e5cccb7c 100644
--- a/src/eslint/linter.ts
+++ b/src/eslint/linter.ts
@@ -7,7 +7,8 @@
  * @author aladdin-add
  */
 
-import { Linter, Rule } from 'eslint';
+import { Rule } from 'eslint';
+import { LegacyESLint } from 'eslint/use-at-your-own-risk';
 import { FixContext } from '../fix/index.js';
 import { ruleFixer } from './rule-fixer.js';
 import { SourceCodeFixer } from './source-code-fixer.js';
@@ -24,14 +25,13 @@ type FixedResult = {
  * @param linter
  */
 // eslint-disable-next-line max-params
-export function verifyAndFix(
-  linter: Linter,
+export async function verifyAndFix(
+  eslint: LegacyESLint,
   text: string,
-  config: Linter.Config | Linter.FlatConfig[],
   filePath: string,
   ruleIds: string[],
   fixCreator: (context: FixContext) => Rule.Fix[],
-): FixedResult {
+): Promise<FixedResult> {
   let fixedResult: FixedResult;
   let fixed = false;
   let passNumber = 0;
@@ -49,10 +49,12 @@ export function verifyAndFix(
   do {
     passNumber++;
 
-    const messages = linter
-      .verify(currentText, config, filePath)
+    // eslint-disable-next-line no-await-in-loop
+    const results = await eslint.lintText(currentText, { filePath });
+    const messages = results
+      .flatMap((result) => result.messages)
       .filter((message) => message.ruleId && ruleIds.includes(message.ruleId));
-    const sourceCode = linter.getSourceCode();
+    const sourceCode = null as any; // TODO: Get `SourceCode` from `eslint`
 
     // Create `Rule.Fix[]`
     const fixContext: FixContext = {

From 32cc68a4ad932a972d14117593f67ecf29a0a048 Mon Sep 17 00:00:00 2001
From: mizdra <pp.mizdra@gmail.com>
Date: Thu, 26 Sep 2024 00:01:32 +0900
Subject: [PATCH 5/7] improve vscode config

---
 .vscode/settings.json | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.vscode/settings.json b/.vscode/settings.json
index ee73d13a..c3c3b3bb 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -4,6 +4,8 @@
   "editor.codeActionsOnSave": {
     "source.fixAll.eslint": "explicit"
   },
+  "typescript.preferences.importModuleSpecifier": "relative",
+  "javascript.preferences.importModuleSpecifier": "relative",
   "files.exclude": {
     "**/.git": true,
     "**/.svn": true,

From 43d9e339d8039e8f520fe12c0bab5d321b9f0d5c Mon Sep 17 00:00:00 2001
From: mizdra <pp.mizdra@gmail.com>
Date: Thu, 26 Sep 2024 00:04:35 +0900
Subject: [PATCH 6/7] get `SourceCode` instance from custom rule

---
 src/core.ts          | 31 +++++++++++++++++--
 src/eslint/linter.ts |  4 ++-
 src/plugin.ts        | 71 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 102 insertions(+), 4 deletions(-)
 create mode 100644 src/plugin.ts

diff --git a/src/core.ts b/src/core.ts
index 2c5e7da9..9a0afb15 100644
--- a/src/core.ts
+++ b/src/core.ts
@@ -18,6 +18,7 @@ import {
   verifyAndFix,
 } from './fix/index.js';
 import { format } from './formatter/index.js';
+import { plugin } from './plugin.js';
 import { filterResultsByRuleId } from './util/eslint.js';
 
 const { LegacyESLint, FlatESLint } = eslintPkg;
@@ -51,15 +52,39 @@ export class Core {
       const { type, ...rest } = eslintOptions;
       this.eslint = new LegacyESLint({
         ...rest,
-        plugins: {},
+        plugins: {
+          ...rest.plugins,
+          'eslint-interactive': plugin,
+        },
         overrideConfig: {
           ...rest.overrideConfig,
-          plugins: [...(rest.overrideConfig?.plugins ?? []), 'eslint-plugin-eslint-interactive'],
+          plugins: [...(rest.overrideConfig?.plugins ?? []), 'eslint-interactive'],
+          rules: {
+            ...rest.overrideConfig?.rules,
+            'eslint-interactive/source-code-snatcher': 'error',
+          },
         },
       });
     } else {
       const { type, ...rest } = eslintOptions;
-      this.eslint = new FlatESLint(rest);
+      const overrideConfigs = Array.isArray(rest.overrideConfig)
+        ? rest.overrideConfig
+        : rest.overrideConfig
+        ? [rest.overrideConfig]
+        : [];
+      this.eslint = new FlatESLint({
+        ...rest,
+        overrideConfig: [
+          ...overrideConfigs,
+          {
+            ...rest.overrideConfig,
+            plugins: { 'eslint-interactive': plugin },
+            rules: {
+              'eslint-interactive/source-code-snatcher': 'error',
+            },
+          },
+        ],
+      });
     }
   }
 
diff --git a/src/eslint/linter.ts b/src/eslint/linter.ts
index e5cccb7c..dd13621e 100644
--- a/src/eslint/linter.ts
+++ b/src/eslint/linter.ts
@@ -10,6 +10,7 @@
 import { Rule } from 'eslint';
 import { LegacyESLint } from 'eslint/use-at-your-own-risk';
 import { FixContext } from '../fix/index.js';
+import { getLastSourceCode } from '../plugin.js';
 import { ruleFixer } from './rule-fixer.js';
 import { SourceCodeFixer } from './source-code-fixer.js';
 
@@ -54,7 +55,8 @@ export async function verifyAndFix(
     const messages = results
       .flatMap((result) => result.messages)
       .filter((message) => message.ruleId && ruleIds.includes(message.ruleId));
-    const sourceCode = null as any; // TODO: Get `SourceCode` from `eslint`
+    const sourceCode = getLastSourceCode();
+    if (!sourceCode) throw new Error('Failed to get the last source code.');
 
     // Create `Rule.Fix[]`
     const fixContext: FixContext = {
diff --git a/src/plugin.ts b/src/plugin.ts
new file mode 100644
index 00000000..0bb0f923
--- /dev/null
+++ b/src/plugin.ts
@@ -0,0 +1,71 @@
+import { ESLint, Rule, SourceCode } from 'eslint';
+
+let lastSourceCode: SourceCode | null = null;
+
+export function getLastSourceCode() {
+  return lastSourceCode;
+}
+
+export const plugin: ESLint.Plugin = {
+  rules: {
+    /**
+     * This is a rule for getting a `SourceCode` instance.
+     * `ESLint` class does not provide a method for getting a `SourceCode` instance. As an alternative, we have prepared this custom rule.
+     */
+    'source-code-snatcher': {
+      create(context) {
+        lastSourceCode = context.sourceCode;
+        return {};
+      },
+    },
+    /** This is a rule for testing purposes. */
+    'prefer-addition-shorthand': {
+      meta: {
+        type: 'suggestion',
+        // @ts-ignore
+        hasSuggestions: true,
+      },
+      create(context: Rule.RuleContext) {
+        return {
+          // eslint-disable-next-line @typescript-eslint/naming-convention
+          AssignmentExpression: (node) => {
+            if (node.left.type !== 'Identifier') return;
+            const leftIdentifier = node.left;
+            if (node.right.type !== 'BinaryExpression') return;
+            const rightBinaryExpression = node.right;
+            if (rightBinaryExpression.operator !== '+') return;
+            if (rightBinaryExpression.left.type !== 'Identifier') return;
+            const rightIdentifier = rightBinaryExpression.left;
+            if (leftIdentifier.name !== rightIdentifier.name) return;
+            if (rightBinaryExpression.right.type !== 'Literal' || rightBinaryExpression.right.value !== 1) return;
+
+            context.report({
+              node,
+              message: 'The addition method is redundant.',
+              suggest: [
+                {
+                  desc: 'Use `val += 1` instead.',
+                  fix(fixer) {
+                    return fixer.replaceText(node, `${leftIdentifier.name} += 1`);
+                  },
+                },
+                {
+                  desc: 'Use `val++` instead.',
+                  fix(fixer) {
+                    return fixer.replaceText(node, `${leftIdentifier.name}++`);
+                  },
+                },
+                {
+                  desc: 'Use `++val` instead.',
+                  fix(fixer) {
+                    return fixer.replaceText(node, `++${leftIdentifier.name}`);
+                  },
+                },
+              ],
+            });
+          },
+        };
+      },
+    },
+  },
+};

From 056228fe4fb81252274425a05c7074e8d4fc9eff Mon Sep 17 00:00:00 2001
From: mizdra <pp.mizdra@gmail.com>
Date: Thu, 26 Sep 2024 00:05:39 +0900
Subject: [PATCH 7/7] fix broken test cases

---
 src/__snapshots__/core.test.ts.snap           |  9 ---
 .../apply-suggestions.test.ts.snap            |  6 +-
 src/fix/apply-auto-fixes.test.ts              | 16 ++---
 src/fix/apply-suggestions.test.ts             | 40 ++++++-------
 .../convert-error-to-warning-per-file.test.ts | 32 +++++-----
 src/fix/disable-per-file.test.ts              | 44 +++++++-------
 src/fix/disable-per-line.test.ts              | 60 +++++++++----------
 src/fix/make-fixable-and-fix.test.ts          | 28 ++++-----
 src/test-util/fix-tester.ts                   | 32 ++++++----
 .../prefer-addition-shorthand-rule.ts         | 54 -----------------
 10 files changed, 132 insertions(+), 189 deletions(-)
 delete mode 100644 src/test-util/prefer-addition-shorthand-rule.ts

diff --git a/src/__snapshots__/core.test.ts.snap b/src/__snapshots__/core.test.ts.snap
index 4444aa26..03ed8e24 100644
--- a/src/__snapshots__/core.test.ts.snap
+++ b/src/__snapshots__/core.test.ts.snap
@@ -71,15 +71,6 @@ let a = 1;"
 
 exports[`Core > fixes problems with legacy config and 3rd-party plugins 1`] = `
 "// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
-// eslint-disable-next-line test/ban-nullish-coalescing-operator
 2 ?? 2;"
 `;
 
diff --git a/src/fix/__snapshots__/apply-suggestions.test.ts.snap b/src/fix/__snapshots__/apply-suggestions.test.ts.snap
index 53daa1fc..8f84b96a 100644
--- a/src/fix/__snapshots__/apply-suggestions.test.ts.snap
+++ b/src/fix/__snapshots__/apply-suggestions.test.ts.snap
@@ -22,7 +22,7 @@ exports[`apply-suggestions > filter には suggestions, message が渡ってく
         "line": 1,
         "message": "The addition method is redundant.",
         "nodeType": "AssignmentExpression",
-        "ruleId": "prefer-addition-shorthand",
+        "ruleId": "eslint-interactive/prefer-addition-shorthand",
         "severity": 2,
         "suggestions": [
           {
@@ -59,7 +59,7 @@ exports[`apply-suggestions > filter には suggestions, message が渡ってく
       },
     ],
     "ruleIds": [
-      "prefer-addition-shorthand",
+      "eslint-interactive/prefer-addition-shorthand",
     ],
     "sourceCode": {
       "text": "a = a + 1;",
@@ -72,7 +72,7 @@ exports[`apply-suggestions > filter には suggestions, message が渡ってく
     "line": 1,
     "message": "The addition method is redundant.",
     "nodeType": "AssignmentExpression",
-    "ruleId": "prefer-addition-shorthand",
+    "ruleId": "eslint-interactive/prefer-addition-shorthand",
     "severity": 2,
     "suggestions": [
       {
diff --git a/src/fix/apply-auto-fixes.test.ts b/src/fix/apply-auto-fixes.test.ts
index ba027106..7c672f85 100644
--- a/src/fix/apply-auto-fixes.test.ts
+++ b/src/fix/apply-auto-fixes.test.ts
@@ -9,25 +9,25 @@ const tester = new FixTester(
 );
 
 describe('apply-auto-fixes', () => {
-  test('basic', () => {
+  test('basic', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { semi: 'error' },
       }),
     ).toMatchInlineSnapshot(`"var val;"`);
   });
-  test('同一行にて複数の rule を同時に fix できる', () => {
+  test('同一行にて複数の rule を同時に fix できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { 'semi': 'error', 'no-var': 'error' },
       }),
     ).toMatchInlineSnapshot(`"let val;"`);
   });
-  test('複数行を同時に fix できる', () => {
+  test('複数行を同時に fix できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['var val1', 'var val2', '', 'var val3'],
         rules: { semi: 'error' },
       }),
@@ -38,9 +38,9 @@ describe('apply-auto-fixes', () => {
       var val3;"
     `);
   });
-  test('fixable な problem がない場合は何もしない', () => {
+  test('fixable な problem がない場合は何もしない', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val;',
         rules: { semi: 'error' },
       }),
diff --git a/src/fix/apply-suggestions.test.ts b/src/fix/apply-suggestions.test.ts
index e01a27eb..8fb25bc6 100644
--- a/src/fix/apply-suggestions.test.ts
+++ b/src/fix/apply-suggestions.test.ts
@@ -10,20 +10,20 @@ const tester = new FixTester<FixToApplySuggestionsArgs>(
 );
 
 describe('apply-suggestions', () => {
-  test('basic', () => {
+  test('basic', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'a = a + 1;',
-        rules: { 'prefer-addition-shorthand': 'error' },
+        rules: { 'eslint-interactive/prefer-addition-shorthand': 'error' },
         args: { filter: (suggestions) => suggestions[0] },
       }),
     ).toMatchInlineSnapshot(`"a += 1;"`);
   });
-  test('一度に複数の suggestion を適用できる', () => {
+  test('一度に複数の suggestion を適用できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['a = a + 1;', 'b = b + 1;'],
-        rules: { 'prefer-addition-shorthand': 'error' },
+        rules: { 'eslint-interactive/prefer-addition-shorthand': 'error' },
         args: { filter: (suggestions) => suggestions[0] },
       }),
     ).toMatchInlineSnapshot(`
@@ -31,11 +31,11 @@ describe('apply-suggestions', () => {
       b += 1;"
     `);
   });
-  test('一度に複数の rule の suggestion を適用できる', () => {
+  test('一度に複数の rule の suggestion を適用できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['a = a + 1;', 'if (!key in object) {}'],
-        rules: { 'prefer-addition-shorthand': 'error', 'no-unsafe-negation': 'error' },
+        rules: { 'eslint-interactive/prefer-addition-shorthand': 'error', 'no-unsafe-negation': 'error' },
         args: { filter: (suggestions) => suggestions[0] },
       }),
     ).toMatchInlineSnapshot(`
@@ -43,19 +43,19 @@ describe('apply-suggestions', () => {
       if (!(key in object)) {}"
     `);
   });
-  test('1 つの行に複数の suggestion があっても全ての suggestion が適用できる', () => {
+  test('1 つの行に複数の suggestion があっても全ての suggestion が適用できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['a = a + 1; b = b + 1;'],
-        rules: { 'prefer-addition-shorthand': 'error' },
+        rules: { 'eslint-interactive/prefer-addition-shorthand': 'error' },
         args: { filter: (suggestions) => suggestions[0] },
       }),
     ).toMatchInlineSnapshot(`"a += 1; b += 1;"`);
   });
-  test('filter には suggestions, message が渡ってくる', () => {
-    tester.test({
+  test('filter には suggestions, message が渡ってくる', async () => {
+    await tester.test({
       code: ['a = a + 1;'],
-      rules: { 'prefer-addition-shorthand': 'error' },
+      rules: { 'eslint-interactive/prefer-addition-shorthand': 'error' },
       args: {
         filter: (suggestions, message, context) => {
           expect({
@@ -74,20 +74,20 @@ describe('apply-suggestions', () => {
       },
     });
   });
-  test('suggestion がない場合は何もしない', () => {
+  test('suggestion がない場合は何もしない', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'a = a + 1;',
         rules: { semi: 'error' },
         args: { filter: (suggestions) => suggestions[0] },
       }),
     ).toMatchInlineSnapshot(`null`);
   });
-  test('filter から null もしくは undefined を返すと、suggestion は適用されない', () => {
+  test('filter から null もしくは undefined を返すと、suggestion は適用されない', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'a = a + 1;',
-        rules: { 'prefer-addition-shorthand': 'error' },
+        rules: { 'eslint-interactive/prefer-addition-shorthand': 'error' },
         args: { filter: (_suggestions) => (Math.random() < 0.5 ? null : undefined) },
       }),
     ).toMatchInlineSnapshot(`null`);
diff --git a/src/fix/convert-error-to-warning-per-file.test.ts b/src/fix/convert-error-to-warning-per-file.test.ts
index caccae30..9911ae83 100644
--- a/src/fix/convert-error-to-warning-per-file.test.ts
+++ b/src/fix/convert-error-to-warning-per-file.test.ts
@@ -9,9 +9,9 @@ const tester = new FixTester(
 );
 
 describe('convert-error-to-warning-per-file', () => {
-  test('basic', () => {
+  test('basic', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { semi: 'error' },
       }),
@@ -20,9 +20,9 @@ describe('convert-error-to-warning-per-file', () => {
       var val"
     `);
   });
-  test('fixes multiple rules', () => {
+  test('fixes multiple rules', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { 'semi': 'error', 'no-var': 'error' },
       }),
@@ -31,9 +31,9 @@ describe('convert-error-to-warning-per-file', () => {
       var val"
     `);
   });
-  test('can add description', () => {
+  test('can add description', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { semi: 'error' },
         args: { description: 'comment' },
@@ -43,17 +43,17 @@ describe('convert-error-to-warning-per-file', () => {
       var val"
     `);
   });
-  test('ignores warnings', () => {
+  test('ignores warnings', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* eslint semi: 1 */', 'var val'],
         rules: { semi: 'error' },
       }),
     ).toMatchInlineSnapshot(`null`);
   });
-  test('combines directives into one', () => {
+  test('combines directives into one', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['var val', 'var val'],
         rules: { semi: 'error' },
       }),
@@ -63,9 +63,9 @@ describe('convert-error-to-warning-per-file', () => {
       var val"
     `);
   });
-  test('`eslint` directive has precedence over `@ts-check`', () => {
+  test('`eslint` directive has precedence over `@ts-check`', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['// @ts-check', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -75,9 +75,9 @@ describe('convert-error-to-warning-per-file', () => {
       var val"
     `);
   });
-  test('`eslint` directive has precedence over `/* @jsxImportSource xxx */`', () => {
+  test('`eslint` directive has precedence over `/* @jsxImportSource xxx */`', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* @jsxImportSource @emotion/react */', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -87,9 +87,9 @@ describe('convert-error-to-warning-per-file', () => {
       var val"
     `);
   });
-  test('The shebang has precedence over `eslint` directive', () => {
+  test('The shebang has precedence over `eslint` directive', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['#!/usr/bin/env node', 'var val'],
         rules: { 'no-var': 'error' },
       }),
diff --git a/src/fix/disable-per-file.test.ts b/src/fix/disable-per-file.test.ts
index a497f776..f3991c21 100644
--- a/src/fix/disable-per-file.test.ts
+++ b/src/fix/disable-per-file.test.ts
@@ -9,9 +9,9 @@ const tester = new FixTester(
 );
 
 describe('disable-per-file', () => {
-  test('basic', () => {
+  test('basic', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { semi: 'error' },
       }),
@@ -20,9 +20,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('複数の rule を同時に disable できる', () => {
+  test('複数の rule を同時に disable できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { 'semi': 'error', 'no-var': 'error' },
       }),
@@ -31,9 +31,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('既に disable comment が付いている場合は、末尾に足す', () => {
+  test('既に disable comment が付いている場合は、末尾に足す', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* eslint-disable semi */', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -42,9 +42,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('disable description があっても disable できる', () => {
+  test('disable description があっても disable できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* eslint-disable semi -- comment */', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -53,9 +53,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('disable description を追加できる', () => {
+  test('disable description を追加できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* eslint-disable semi */', 'var val'],
         rules: { 'no-var': 'error' },
         args: { description: 'comment' },
@@ -65,9 +65,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('既に disable description があるコメントに対しても disable description を追加できる', () => {
+  test('既に disable description があるコメントに対しても disable description を追加できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* eslint-disable semi -- foo */', 'var val'],
         rules: { 'no-var': 'error' },
         args: { description: 'bar' },
@@ -77,9 +77,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('add a description to the line before the disable comment if there is already disable comment', () => {
+  test('add a description to the line before the disable comment if there is already disable comment', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* eslint-disable semi -- foo */', 'var val'],
         rules: { 'no-var': 'error' },
         args: { description: 'bar', descriptionPosition: 'previousLine' },
@@ -90,9 +90,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('add a description comment before the line with the problem', () => {
+  test('add a description comment before the line with the problem', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['var val'],
         rules: { semi: 'error' },
         args: { description: 'foo', descriptionPosition: 'previousLine' },
@@ -103,9 +103,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('`eslint-disable` has precedence over `@ts-check`', () => {
+  test('`eslint-disable` has precedence over `@ts-check`', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['// @ts-check', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -115,9 +115,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('`eslint-disable` has precedence over `/* @jsxImportSource xxx */`', () => {
+  test('`eslint-disable` has precedence over `/* @jsxImportSource xxx */`', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* @jsxImportSource @emotion/react */', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -127,9 +127,9 @@ describe('disable-per-file', () => {
       var val"
     `);
   });
-  test('The shebang has precedence over `eslint-disable`', () => {
+  test('The shebang has precedence over `eslint-disable`', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['#!/usr/bin/env node', 'var val'],
         rules: { 'no-var': 'error' },
       }),
diff --git a/src/fix/disable-per-line.test.ts b/src/fix/disable-per-line.test.ts
index 745b8109..d4161602 100644
--- a/src/fix/disable-per-line.test.ts
+++ b/src/fix/disable-per-line.test.ts
@@ -11,9 +11,9 @@ const tester = new FixTester(
 );
 
 describe('disable-per-line', () => {
-  test('basic', () => {
+  test('basic', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { semi: 'error' },
       }),
@@ -22,9 +22,9 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('同一行にて複数の rule を同時に disable できる', () => {
+  test('同一行にて複数の rule を同時に disable できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'var val',
         rules: { 'semi': 'error', 'no-var': 'error' },
       }),
@@ -33,9 +33,9 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('既に disable comment が付いている場合は、末尾に足す', () => {
+  test('既に disable comment が付いている場合は、末尾に足す', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['// eslint-disable-next-line semi', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -44,17 +44,17 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('既に disable されている場合は何もしない', () => {
+  test('既に disable されている場合は何もしない', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['// eslint-disable-next-line semi', 'var val'],
         rules: { semi: 'error' },
       }),
     ).toMatchInlineSnapshot(`null`);
   });
-  test('`/* ... */` スタイルであっても disable できる', () => {
+  test('`/* ... */` スタイルであっても disable できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['/* eslint-disable-next-line semi */', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -63,9 +63,9 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('disable description があっても disable できる', () => {
+  test('disable description があっても disable できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['// eslint-disable-next-line semi -- comment', 'var val'],
         rules: { 'no-var': 'error' },
       }),
@@ -74,9 +74,9 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('disable description を追加できる', () => {
+  test('disable description を追加できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['// eslint-disable-next-line semi', 'var val'],
         rules: { 'no-var': 'error' },
         args: { description: 'comment' },
@@ -86,9 +86,9 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('既に disable description があるコメントに対しても disable description を追加できる', () => {
+  test('既に disable description があるコメントに対しても disable description を追加できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['// eslint-disable-next-line semi -- foo', 'var val'],
         rules: { 'no-var': 'error' },
         args: { description: 'bar' },
@@ -98,9 +98,9 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('add a description to the line before the disable comment if there is already disable comment', () => {
+  test('add a description to the line before the disable comment if there is already disable comment', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['// eslint-disable-next-line semi -- foo', 'var val'],
         rules: { 'no-var': 'error' },
         args: { description: 'bar', descriptionPosition: 'previousLine' },
@@ -111,9 +111,9 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('add a description comment before the line with the problem', () => {
+  test('add a description comment before the line with the problem', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['var val'],
         rules: { semi: 'error' },
         args: { description: 'foo', descriptionPosition: 'previousLine' },
@@ -124,9 +124,9 @@ describe('disable-per-line', () => {
       var val"
     `);
   });
-  test('複数行を同時に disable できる', () => {
+  test('複数行を同時に disable できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['var val1', 'var val2', '', 'var val3'],
         rules: { 'no-var': 'error' },
       }),
@@ -141,9 +141,9 @@ describe('disable-per-line', () => {
     `);
   });
   describe('add a disable comment for JSX', () => {
-    test('when descriptionPosition is sameLine', () => {
+    test('when descriptionPosition is sameLine', async () => {
       expect(
-        tester.test({
+        await tester.test({
           code: [
             'var jsx = <div>',
             '  <span>text1</span>',
@@ -173,9 +173,9 @@ describe('disable-per-line', () => {
         </div>;"
       `);
     });
-    test('when descriptionPosition is previousLine', () => {
+    test('when descriptionPosition is previousLine', async () => {
       expect(
-        tester.test({
+        await tester.test({
           code: [
             'var jsx = <div>',
             '  <span>text1</span>',
@@ -210,9 +210,9 @@ describe('disable-per-line', () => {
       `);
     });
   });
-  test('disable comment のある行に disable comment 以外の Node があっても disable できる', () => {
+  test('disable comment のある行に disable comment 以外の Node があっても disable できる', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: [
           'var val1; // eslint-disable-next-line semi',
           'var val2;',
@@ -235,9 +235,9 @@ describe('disable-per-line', () => {
       var val6;"
     `);
   });
-  test('supports auto-indent', () => {
+  test('supports auto-indent', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: [
           '{',
           '  void 0;',
diff --git a/src/fix/make-fixable-and-fix.test.ts b/src/fix/make-fixable-and-fix.test.ts
index 52c77ed3..5ff2ee0e 100644
--- a/src/fix/make-fixable-and-fix.test.ts
+++ b/src/fix/make-fixable-and-fix.test.ts
@@ -18,9 +18,9 @@ const tester = new FixTester<FixToMakeFixableAndFixArgs>(
 );
 
 describe('make-fixable-and-fix', () => {
-  test('basic', () => {
+  test('basic', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'const a = 1;',
         rules: { 'no-unused-vars': ['error', { varsIgnorePattern: '^_' }] },
         args: {
@@ -32,9 +32,9 @@ describe('make-fixable-and-fix', () => {
       }),
     ).toMatchInlineSnapshot(`"const _a = 1;"`);
   });
-  test('can process multiple messages at once', () => {
+  test('can process multiple messages at once', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['const a = 1;', 'const b = 2;'],
         rules: { 'no-unused-vars': ['error', { varsIgnorePattern: '^_' }] },
         args: {
@@ -49,9 +49,9 @@ describe('make-fixable-and-fix', () => {
       const _b = 2;"
     `);
   });
-  test('can process messages of multiple rules at once', () => {
+  test('can process messages of multiple rules at once', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['const a = 1;', 'let b = 2;', 'b++;', 'console.log(b);'],
         rules: { 'no-unused-vars': ['error', { varsIgnorePattern: '^_' }], 'no-plusplus': 'error' },
         args: {
@@ -74,9 +74,9 @@ describe('make-fixable-and-fix', () => {
       console.log(b);"
     `);
   });
-  test('can process messages on the same line', () => {
+  test('can process messages on the same line', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: ['const a = 1; const b = 2;'],
         rules: { 'no-unused-vars': ['error', { varsIgnorePattern: '^_' }] },
         args: {
@@ -88,8 +88,8 @@ describe('make-fixable-and-fix', () => {
       }),
     ).toMatchInlineSnapshot(`"const _a = 1; const _b = 2;"`);
   });
-  test('`fixableMaker` receives the message and node.', () => {
-    tester.test({
+  test('`fixableMaker` receives the message and node.', async () => {
+    await tester.test({
       code: ['const a = 1;'],
       rules: { 'no-unused-vars': ['error', { varsIgnorePattern: '^_' }] },
       args: {
@@ -110,8 +110,8 @@ describe('make-fixable-and-fix', () => {
       },
     });
   });
-  test('node is null if message is not associated with a node', () => {
-    tester.test({
+  test('node is null if message is not associated with a node', async () => {
+    await tester.test({
       code: ['// this is comment'],
       rules: { 'capitalized-comments': 'error' },
       args: {
@@ -122,9 +122,9 @@ describe('make-fixable-and-fix', () => {
       },
     });
   });
-  test('do not process if `fixableMaker` returns null', () => {
+  test('do not process if `fixableMaker` returns null', async () => {
     expect(
-      tester.test({
+      await tester.test({
         code: 'const a = 1;',
         rules: { 'no-unused-vars': ['error', { varsIgnorePattern: '^_' }] },
         args: {
diff --git a/src/test-util/fix-tester.ts b/src/test-util/fix-tester.ts
index c840010e..85dfde0e 100644
--- a/src/test-util/fix-tester.ts
+++ b/src/test-util/fix-tester.ts
@@ -1,7 +1,8 @@
 import { Linter, Rule } from 'eslint';
+import { LegacyESLint } from 'eslint/use-at-your-own-risk';
 import { verifyAndFix } from '../eslint/linter.js';
 import { FixContext } from '../fix/index.js';
-import { preferAdditionShorthandRule } from './prefer-addition-shorthand-rule.js';
+import { plugin } from '../plugin.js';
 
 const DEFAULT_FILENAME = 'test.js';
 
@@ -33,7 +34,6 @@ type TestResult = string | null;
  * The test utility for the fix.
  */
 export class FixTester<FixArgs> {
-  private linter: Linter;
   private fixCreator: (context: FixContext, args: FixArgs) => Rule.Fix[];
   private defaultFixArgs: FixArgs;
   private defaultLinterConfig: Linter.Config;
@@ -42,8 +42,6 @@ export class FixTester<FixArgs> {
     defaultFixArgs: FixArgs,
     defaultLinterConfig: Linter.Config,
   ) {
-    this.linter = new Linter({ configType: 'eslintrc' });
-    this.linter.defineRule('prefer-addition-shorthand', preferAdditionShorthandRule);
     this.fixCreator = fixCreator;
     this.defaultFixArgs = defaultFixArgs;
     this.defaultLinterConfig = defaultLinterConfig;
@@ -53,20 +51,28 @@ export class FixTester<FixArgs> {
    * @param testCase The test case.
    * @returns The fixed code. If the fix skipped, null is returned.
    */
-  test(testCase: TestCase<FixArgs>): TestResult {
+  async test(testCase: TestCase<FixArgs>): Promise<TestResult> {
     const code = Array.isArray(testCase.code) ? testCase.code.join('\n') : testCase.code;
 
     const filePath = testCase.filename ?? DEFAULT_FILENAME;
 
-    const config: Linter.Config = {
-      ...this.defaultLinterConfig,
-      rules: {
-        ...this.defaultLinterConfig.rules,
-        ...testCase.rules,
-      },
-    };
     const ruleIdsToFix = Object.keys(testCase.rules);
-    const fixedResult = verifyAndFix(this.linter, code, config, filePath, ruleIdsToFix, (context) =>
+    const eslint = new LegacyESLint({
+      useEslintrc: false,
+      plugins: {
+        'eslint-interactive': plugin,
+      },
+      overrideConfig: {
+        ...this.defaultLinterConfig,
+        plugins: ['eslint-interactive', ...(this.defaultLinterConfig.plugins ?? [])],
+        rules: {
+          ...this.defaultLinterConfig.rules,
+          ...testCase.rules,
+          'eslint-interactive/source-code-snatcher': 'error',
+        },
+      },
+    });
+    const fixedResult = await verifyAndFix(eslint, code, filePath, ruleIdsToFix, (context) =>
       this.fixCreator(context, testCase.args ?? this.defaultFixArgs),
     );
 
diff --git a/src/test-util/prefer-addition-shorthand-rule.ts b/src/test-util/prefer-addition-shorthand-rule.ts
deleted file mode 100644
index 7f628461..00000000
--- a/src/test-util/prefer-addition-shorthand-rule.ts
+++ /dev/null
@@ -1,54 +0,0 @@
-import { Rule } from 'eslint';
-
-/**
- * @file This is a rule for testing purposes.
- */
-
-export const preferAdditionShorthandRule: Rule.RuleModule = {
-  meta: {
-    type: 'suggestion',
-    // @ts-ignore
-    hasSuggestions: true,
-  },
-  create(context: Rule.RuleContext) {
-    return {
-      // eslint-disable-next-line @typescript-eslint/naming-convention
-      AssignmentExpression: (node) => {
-        if (node.left.type !== 'Identifier') return;
-        const leftIdentifier = node.left;
-        if (node.right.type !== 'BinaryExpression') return;
-        const rightBinaryExpression = node.right;
-        if (rightBinaryExpression.operator !== '+') return;
-        if (rightBinaryExpression.left.type !== 'Identifier') return;
-        const rightIdentifier = rightBinaryExpression.left;
-        if (leftIdentifier.name !== rightIdentifier.name) return;
-        if (rightBinaryExpression.right.type !== 'Literal' || rightBinaryExpression.right.value !== 1) return;
-
-        context.report({
-          node,
-          message: 'The addition method is redundant.',
-          suggest: [
-            {
-              desc: 'Use `val += 1` instead.',
-              fix(fixer) {
-                return fixer.replaceText(node, `${leftIdentifier.name} += 1`);
-              },
-            },
-            {
-              desc: 'Use `val++` instead.',
-              fix(fixer) {
-                return fixer.replaceText(node, `${leftIdentifier.name}++`);
-              },
-            },
-            {
-              desc: 'Use `++val` instead.',
-              fix(fixer) {
-                return fixer.replaceText(node, `++${leftIdentifier.name}`);
-              },
-            },
-          ],
-        });
-      },
-    };
-  },
-};