eslint-tester

const ESLintTester = require('eslint-tester'); // Mock a simple ESLint rule for demonstration const myCustomRule = { meta: { type: 'suggestion', schema: [], messages: { avoidFoo: 'Avoid using the identifier `foo`.' } }, create(context) { return { Identifier(node) { if (node.name === 'foo') { context.report({ node, messageId: 'avoidFoo' }); } } }; } }; // Instantiate ESLintTester (note: actual usage would involve an ESLint config) // This is a simplified example based on internal testing patterns. // In a real scenario, you'd pass a configured ESLint instance or path to rules. // As this package is deprecated, detailed external API examples are scarce. const tester = new ESLintTester(); // An example of a valid test case (no errors expected) const validCase = { code: 'const bar = 1;', parserOptions: { ecmaVersion: 6 } }; // An example of an invalid test case (errors expected) const invalidCase = { code: 'const foo = 2;', parserOptions: { ecmaVersion: 6 }, errors: [{ messageId: 'avoidFoo', line: 1, column: 7 }] }; // Run a test (this API is inferred and might not match direct public usage perfectly for older versions) // The actual `eslint-tester` API is complex and meant for internal ESLint use. // For modern rule testing, use `RuleTester` directly from `eslint`. console.log('Running tests...'); // This part of the quickstart is conceptual as eslint-tester's public API for rule testing is not straightforward. // Its primary use was internal to ESLint development. // For actual rule testing, one would register rules and then run tests, similar to RuleTester. // const results = tester.run('my-custom-rule', myCustomRule, { valid: [validCase], invalid: [invalidCase] }); // console.log(results); console.log('`eslint-tester` is deprecated. Use `RuleTester` from `eslint` for modern rule testing.'); console.log('A complete runnable example for `eslint-tester` is difficult due to its internal-focused API and deprecation.');