feat(rule): add no-focused-tests rule

docs/rules/no-focused-tests.md

@@ -0,0 +1,30 @@
+# Disallow focused tests (no-focused-tests)
+
+Inspired by the [`no-focused-tests` rule in `eslint-plugin-jest`](https://github.com/jest-community/eslint-plugin-jest/blob/19e3a6e7b71a25881b7b75531f2d8aad32d9d589/docs/rules/no-focused-tests.md), this rule reminds you to remove `.only` from your Cypress tests.
+
+## Rule Details
+
+This rule detects occurrences of `describe.only` and `it.only` in the source code.
+
+Examples of **incorrect** code for this rule:
+
+```js
+describe.only(('my describe block'), () => {
+    it('works', () => {});
+});
+describe(('my describe block'), () => {
+    it.only('works', () => {});
+});
+```
+
+Examples of **correct** code for this rule:
+
+```js
+describe(('my describe block'), () => {
+    it('works', () => {});
+});
+```
+
+## When Not To Use It
+
+If you want to run only one test case and/or describe block, you may not want to use this rule.

lib/rules/no-focused-tests.js

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+/**
+ * @fileoverview Disallow focused tests
+ * @author Jonathan Chaffer
+ */
+'use strict'
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'Disallow focused tests',
+      category: 'Possible Errors',
+      recommended: true,
+    },
+    fixable: null, // or "code" or "whitespace"
+    schema: [],
+    messages: {
+      unexpected: 'Do not use focused tests',
+    },
+  },
+
+  create (context) {
+    return {
+      CallExpression (node) {
+        if (!isTestCaseCall(node) && !isDescribeCall(node)) {
+          return
+        }
+
+        const onlyNode = findOnlyNode(node)
+
+        if (!onlyNode) {
+          return
+        }
+
+        context.report({
+          node: onlyNode,
+          messageId: 'unexpected',
+        })
+      },
+    }
+  },
+}
+
+function nodeIsCalledBy (name, node) {
+  if (node.type === 'Identifier' && node.name === name) return true
+
+  if (
+    typeof node.callee === 'undefined' ||
+    typeof node.callee.object === 'undefined'
+  ) {
+    return false
+  }
+
+  return nodeIsCalledBy(name, node.callee.object)
+}
+
+function isDescribeCall (node) {
+  return (
+    node.callee.type === 'MemberExpression' &&
+    nodeIsCalledBy('describe', node) &&
+    node.callee.property.type === 'Identifier'
+  )
+}
+
+function isTestCaseCall (node) {
+  return (
+    node.callee.type === 'MemberExpression' &&
+    nodeIsCalledBy('it', node) &&
+    node.callee.property.type === 'Identifier'
+  )
+}
+
+function findOnlyNode (node) {
+  const callee =
+    node.callee.type === 'TaggedTemplateExpression'
+      ? node.callee.tag
+      : node.callee.type === 'CallExpression'
+        ? node.callee.callee
+        : node.callee
+
+  if (callee.type === 'MemberExpression') {
+    if (callee.object.type === 'MemberExpression') {
+      return callee.object.property
+    }
+
+    return callee.property
+  }
+
+  return null
+}

tests/lib/rules/no-focused-tests.js

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+/**
+ * @fileoverview Disallow focused tests
+ * @author Jonathan Chaffer
+ */
+'use strict'
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+let rule = require('../../../lib/rules/no-focused-tests')
+
+let RuleTester = require('eslint').RuleTester
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+let ruleTester = new RuleTester()
+
+const errors = [{ messageId: 'unexpected' }]
+const parserOptions = { ecmaVersion: 6 }
+
+ruleTester.run('no-focused-tests', rule, {
+
+  valid: [
+    { code: 'it(() => {});', parserOptions },
+    { code: 'describe(() => {});', parserOptions },
+    { code: `describe((\'my describe block\'), () => {
+            it(\'works\', () => {});
+        });`, parserOptions },
+    { code: '\'it.only(() => {})\'', parserOptions },
+  ],
+
+  invalid: [
+    { code: 'it.only(() => {});', parserOptions, errors },
+    { code: 'describe.only(() => {});', parserOptions, errors },
+    { code: `describe.only((\'my describe block\'), () => {
+            it(\'works\', () => {});
+        });`, parserOptions, errors },
+    { code: `describe((\'my describe block\'), () => {
+            it.only(\'works\', () => {});
+        });`, parserOptions, errors },
+  ],
+})