Adds jest/no-if

docs/rules/jest/no-if.md

@@ -0,0 +1,34 @@
+# Prevent if statements in tests. (jest/no-if)
+This rule prevents the use of if statements in tests. 
+
+## Rule Details
+
+If statments in tests is usually an indication that a test is attempting to cover too much. Each branch of code executing within an if statement will likely be better served by a test devoted to it.
+
+Examples of **incorrect** code for this rule:
+
+```js
+it('foo', () => {
+  if('bar') {
+    // an if statement here is invalid
+    // you are probably testing too much
+  }
+})
+
+```
+
+Examples of **correct** code for this rule:
+
+```js
+it('foo', () => {
+  // only test the 'foo' case
+})
+
+it('bar', () => {
+  // test the 'bar' case separately
+})
+```
+
+## When Not To Use It
+
+If you do not wish to prevent the use of if statements in tests, you can safely disable this rule.

lib/rules/jest/no-if.js

@@ -0,0 +1,93 @@
+const {docsUrl} = require('../../utilities');
+
+const TEST_FUNCTION_NAMES = [
+  'it',
+  'xit',
+  'fit',
+  'test',
+  'xtest',
+  'describe',
+  'fdescribe',
+  'xdescribe',
+];
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'Prevent if statements in tests.',
+      category: 'Best Practices',
+      recommended: false,
+      uri: docsUrl('jest/no-if'),
+    },
+    messages: {
+      noIf: [
+        'Tests should not contain if statements.',
+        'This is usually an indication that you',
+        'are attempting to test too much at once',
+        'and may want to consider breaking the if',
+        'statement out into a separate test.',
+      ].join(' '),
+    },
+  },
+
+  create(context) {
+    let inCallExpression = false;
+
+    return {
+      CallExpression(node) {
+        if (notTestFunction(node) || hasEmptyBody(node)) {
+          return;
+        }
+        inCallExpression = true;
+      },
+      IfStatement(node) {
+        if (!inCallExpression) {
+          return;
+        }
+
+        context.report({
+          messageId: 'noIf',
+          node,
+        });
+      },
+      'CallExpression:exit': () => {
+        inCallExpression = false;
+      },
+    };
+  },
+};
+
+function notTestFunction(node) {
+  const method = getMethodName(node);
+  return !matchTestFunctionName(method);
+}
+
+function matchTestFunctionName(functionName) {
+  return TEST_FUNCTION_NAMES.includes(functionName);
+}
+
+function hasEmptyBody(node) {
+  return (
+    node.arguments &&
+    node.arguments.length === 2 &&
+    node.arguments[1].type === 'ArrowFunctionExpression' &&
+    node.arguments[1].body &&
+    node.arguments[1].body.body &&
+    node.arguments[1].body.body.length === 0
+  );
+}
+
+function getMethodName({callee}) {
+  switch (callee.type) {
+    case 'CallExpression':
+      return callee.callee.object
+        ? callee.callee.object.name
+        : callee.callee.name;
+    case 'Identifier':
+      return callee.name;
+    case 'MemberExpression':
+      return callee.object.name;
+    default:
+      return false;
+  }
+}

tests/lib/rules/jest/no-if.js

@@ -0,0 +1,240 @@
+const {RuleTester} = require('eslint');
+const rule = require('../../../../lib/rules/jest/no-if');
+require('babel-eslint');
+
+const parser = 'babel-eslint';
+const ruleTester = new RuleTester();
+
+ruleTester.run('no-if', rule, {
+  valid: [
+    {
+      code: `if(foo) {}`,
+    },
+    {
+      code: `it('foo', () => {})`,
+      parser,
+    },
+    {
+      code: `foo('bar', () => {
+        if(baz) {}
+      })`,
+      parser,
+    },
+  ],
+  invalid: [
+    {
+      code: `it('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `it.skip('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `it.only('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `xit('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `fit('foo', () => {
+          if('bar') {}
+        })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `describe('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `describe.skip('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `describe.only('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `xdescribe.only('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `fdescribe.only('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `test('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `test.skip('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `test.only('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `xtest('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `ftest('foo', () => {
+        if('bar') {}
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `describe('foo', () => {
+        it('bar', () => {
+          if('bar') {}
+        })
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `describe('foo', () => {
+        it('bar', () => {
+          if('bar') {}
+        })
+        it('baz', () => {
+          if('qux') {}
+          if('quux') {}
+        })
+      })`,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+        {
+          messageId: 'noIf',
+        },
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+    {
+      code: `describe('foo', () => {
+          if('bar') {}
+      })
+      if('baz') {}
+      `,
+      parser,
+      errors: [
+        {
+          messageId: 'noIf',
+        },
+      ],
+    },
+  ],
+});

yarn.lock

@@ -3320,10 +3320,10 @@ mem@^1.1.0:
   dependencies:
     mimic-fn "^1.0.0"
 
-merge@1.2.0:
-  version "1.2.0"
-  resolved "https://registry.yarnpkg.com/merge/-/merge-1.2.0.tgz#7531e39d4949c281a66b8c5a6e0265e8b05894da"
-  integrity sha1-dTHjnUlJwoGma4xabgJl6LBYlNo=
+merge@1.2.1:
+  version "1.2.1"
+  resolved "https://registry.yarnpkg.com/merge/-/merge-1.2.1.tgz#38bebf80c3220a8a487b6fcfb3941bb11720c145"
+  integrity sha512-VjFo4P5Whtj4vsLzsYBu5ayHhoHJ0UqNm7ibvShmbmoz7tGi0vXaoJbGdB+GmDMLUdg8DpQXEIeVDAe8MaABvQ==
 
 micromatch@^2.1.5:
   version "2.3.11"