update: check output property is the same as the code property.

Author: aladdin-add

lib/rules/prefer-output-null.js

@@ -27,18 +27,19 @@ module.exports = {
     // Public
     // ----------------------------------------------------------------------
     const message = 'Prefer `output: null` to assert that a test case is not autofixed.';
-
+    const sourceCode = context.getSourceCode();
     return {
       Program (ast) {
         utils.getTestInfo(context, ast).forEach(testRun => {
-          (testRun.invalid || []).forEach(test => {
-            if (!test.properties.some(item => item.key.name === 'output')) {
-              context.report({
-                node: test,
-                message,
-              });
-            }
-          });
+          const reportInfo = utils.getReportInfo(testRun.invalid);
+          const code = sourceCode.getText(reportInfo.code);
+          const output = sourceCode.getText(reportInfo.output);
+          if (output && output === code) {
+            context.report({
+              node: reportInfo.output,
+              message,
+            });
+          }
         });
       },
     };

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

@@ -45,7 +45,7 @@ ruleTester.run('prefer-output-null', rule, {
         new RuleTester().run('foo', bar, {
           valid: [],
           invalid: [
-            {code: 'foo', errors: ['bar']},
+            {code: 'foo', output: 'foo', errors: ['bar']},
           ]
         });
       `,