Update: add --fix to prefer-output-null.

README.md

@@ -56,7 +56,7 @@ Name | ✔️ | 🛠 | Description
 [no-missing-placeholders](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/no-missing-placeholders.md) | ✔️ | | Disallows missing placeholders in rule report messages
 [no-unused-placeholders](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/no-unused-placeholders.md) | ✔️ | | Disallows unused placeholders in rule report messages
 [no-useless-token-range](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/no-useless-token-range.md) | ✔️ | 🛠 | Disallows unnecessary calls to sourceCode.getFirstToken and sourceCode.getLastToken
-[prefer-output-null](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/prefer-output-null.md) | | | Disallows invalid RuleTester test cases with the output the same as the code.
+[prefer-output-null](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/prefer-output-null.md) | | 🛠 | Disallows invalid RuleTester test cases with the output the same as the code.
 [prefer-placeholders](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/prefer-placeholders.md) | | | Disallows template literals as report messages
 [report-message-format](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/report-message-format.md) | | | Enforces a consistent format for report messages
 [require-meta-fixable](https://github.com/not-an-aardvark/eslint-plugin-eslint-plugin/blob/master/docs/rules/require-meta-fixable.md) | ✔️ | | Requires a `meta.fixable` property for fixable rules

docs/rules/prefer-output-null.md

@@ -1,5 +1,7 @@
 # Disallows invalid RuleTester test cases with the output the same as the code. (prefer-output-null)
 
+(fixable) The `--fix` option on the [command line](../user-guide/command-line-interface#fix) automatically fixes problems reported by this rule.
+
 ## Rule Details
 
 The rule reports an error if it encounters a test case where the output is the same as the code.

lib/rules/prefer-output-null.js

@@ -18,7 +18,7 @@ module.exports = {
       category: 'Tests',
       recommended: false,
     },
-    fixable: null,
+    fixable: 'code',
     schema: [],
   },
 
@@ -52,8 +52,9 @@ module.exports = {
 
             if (output && sourceCode.getText(output.value) === sourceCode.getText(code.value)) {
               context.report({
-                node: test,
+                node: output,
                 message,
+                fix: fixer => fixer.replaceText(output.value, 'null'),
               });
             }
           });

tests/lib/rules/prefer-output-null.js

@@ -58,6 +58,14 @@ ruleTester.run('prefer-output-null', rule, {
           ]
         });
       `,
+      output: `
+        new RuleTester().run('foo', bar, {
+          valid: [],
+          invalid: [
+            {code: 'foo', output: null, errors: ['bar']},
+          ]
+        });
+      `,
       errors: [ERROR],
     },
   ],