feat: add lowercase-description rule

jest-community · Feb 11, 2018 · 7d0f175 · 7d0f175
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diff --git a/README.md b/README.md
@@ -81,6 +81,7 @@ for more information about extending configuration files.
 | Rule                                                               | Description                                                     | Recommended                                                             | Fixable                                                     |
 | ------------------------------------------------------------------ | --------------------------------------------------------------- | ----------------------------------------------------------------------- | ----------------------------------------------------------- |
 | [consistent-test-it](docs/rules/consistent-test-it.md)             | Enforce consistent test or it keyword                           |                                                                         | ![fixable](https://img.shields.io/badge/-fixable-green.svg) |
+| [lowercase-description](docs/rules/lowercase-description.md)       | Disallow capitalized `it()` descriptions                        |           |                                                             |
 | [no-disabled-tests](docs/rules/no-disabled-tests.md)               | Disallow disabled tests                                         | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |
 | [no-focused-tests](docs/rules/no-focused-tests.md)                 | Disallow focused tests                                          | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |
 | [no-identical-title](docs/rules/no-identical-title.md)             | Disallow identical titles                                       | ![recommended](https://img.shields.io/badge/-recommended-lightgrey.svg) |                                                             |

diff --git a/docs/rules/lowercase-description.md b/docs/rules/lowercase-description.md
@@ -0,0 +1,21 @@
+# Enforce lowercase descriptions in it() (lowercase-description)
+
+## Rule details
+
+Enforce `it()` tests to have descriptions that begin with a lowercase letter. This provides more readable test failures. This rule is not enabled by default.
+
+The following pattern is considered a warning:
+
+```js
+it('Adds 1 + 2 to equal 3', () => {
+  expect(sum(1, 2)).toBe(3);
+});
+```
+
+The following pattern is not considered a warning:
+
+```js
+it('adds 1 + 2 to equal 3', () => {
+  expect(sum(1, 2)).toBe(3);
+});
+```
diff --git a/index.js b/index.js
@@ -1,6 +1,7 @@
 'use strict';
 
 const consistentTestIt = require('./rules/consistent-test-it');
+const lowercaseDescription = require('./rules/lowercase-description');
 const noDisabledTests = require('./rules/no-disabled-tests');
 const noFocusedTests = require('./rules/no-focused-tests');
 const noIdenticalTitle = require('./rules/no-identical-title');
@@ -59,6 +60,7 @@ module.exports = {
   },
   rules: {
     'consistent-test-it': consistentTestIt,
+    'lowercase-description': lowercaseDescription,
     'no-disabled-tests': noDisabledTests,
     'no-focused-tests': noFocusedTests,
     'no-identical-title': noIdenticalTitle,

diff --git a/rules/__tests__/lowercase-description.test.js b/rules/__tests__/lowercase-description.test.js
@@ -0,0 +1,79 @@
+'use strict';
+
+const RuleTester = require('eslint').RuleTester;
+const rules = require('../..').rules;
+
+const ruleTester = new RuleTester({
+  parserOptions: {
+    ecmaVersion: 6,
+  },
+});
+
+const errMessage =
+  'it(), test() and describe() descriptions should begin with lowercase';
+const errors = [{ message: errMessage, column: 1, line: 1 }];
+
+ruleTester.run('lowercase-description', rules['lowercase-description'], {
+  valid: [
+    "it(' ', function () {})",
+    'it(" ", function () {})',
+    'it(` `, function () {})',
+    "it('foo', function () {})",
+    'it("foo", function () {})',
+    'it(`foo`, function () {})',
+    'it("<Foo/>", function () {})',
+    'it("123 foo", function () {})',
+    'it(42, function () {})',
+    "test('foo', function () {})",
+    'test("foo", function () {})',
+    'test(`foo`, function () {})',
+    'test("<Foo/>", function () {})',
+    'test("123 foo", function () {})',
+    'test("42", function () {})',
+    "describe('foo', function () {})",
+    'describe("foo", function () {})',
+    'describe(`foo`, function () {})',
+    'describe("<Foo/>", function () {})',
+    'describe("123 foo", function () {})',
+    'describe("42", function () {})',
+  ],
+
+  invalid: [
+    {
+      code: "it('Foo', function () {})",
+      errors,
+    },
+    {
+      code: 'it("Foo", function () {})',
+      errors,
+    },
+    {
+      code: 'it(`Foo`, function () {})',
+      errors,
+    },
+    {
+      code: "test('Foo', function () {})",
+      errors,
+    },
+    {
+      code: 'test("Foo", function () {})',
+      errors,
+    },
+    {
+      code: 'test(`Foo`, function () {})',
+      errors,
+    },
+    {
+      code: "describe('Foo', function () {})",
+      errors,
+    },
+    {
+      code: 'describe("Foo", function () {})',
+      errors,
+    },
+    {
+      code: 'describe(`Foo`, function () {})',
+      errors,
+    },
+  ],
+});
diff --git a/rules/lowercase-description.js b/rules/lowercase-description.js
@@ -0,0 +1,65 @@
+'use strict';
+
+const ruleMsg =
+  'it(), test() and describe() descriptions should begin with lowercase';
+
+const isItTestOrDescribeFunction = node => {
+  return (
+    node.type === 'CallExpression' &&
+    node.callee &&
+    (node.callee.name === 'it' ||
+      node.callee.name === 'test' ||
+      node.callee.name === 'describe')
+  );
+};
+
+const isItDescription = node => {
+  return (
+    node.arguments &&
+    node.arguments[0] &&
+    (node.arguments[0].type === 'Literal' ||
+      node.arguments[0].type === 'TemplateLiteral')
+  );
+};
+
+const testDescription = node => {
+  const type = node.arguments[0].type;
+  if (type === 'Literal') {
+    return node.arguments[0].value;
+  }
+  if (type === 'TemplateLiteral') {
+    return node.arguments[0].quasis[0].value.raw;
+  }
+};
+
+const descriptionBeginsWithLowerCase = node => {
+  if (isItTestOrDescribeFunction(node) && isItDescription(node)) {
+    const description = testDescription(node);
+    if (!description[0]) {
+      return true;
+    }
+    return description[0] === description[0].toLowerCase();
+  }
+  return true;
+};
+
+module.exports = {
+  meta: {
+    docs: {
+      url:
+        'https://github.com/jest-community/eslint-plugin-jest/blob/master/docs/rules/lowercase-description.md',
+    },
+  },
+  create(context) {
+    return {
+      CallExpression(node) {
+        if (!descriptionBeginsWithLowerCase(node)) {
+          context.report({
+            message: ruleMsg,
+            node: node,
+          });
+        }
+      },
+    };
+  },
+};