Add prefer-to-be-defined rule

README.md

@@ -32,6 +32,7 @@ Then configure the rules you want to use under the rules section.
     "jest/no-disabled-tests": "warn",
     "jest/no-focused-tests": "error",
     "jest/no-identical-title": "error",
+    "jest/prefer-to-be-defined": "warn",
     "jest/prefer-to-have-length": "warn",
     "jest/valid-expect": "error"
   }
@@ -55,6 +56,8 @@ You can also whitelist the environment variables provided by Jest by doing:
 * [no-focused-tests](/docs/rules/no-focused-tests.md) - disallow focused tests.
 * [no-identical-title](/docs/rules/no-identical-title.md) - disallow identical
   titles.
+* [prefer-to-be-defined](/docs/rules/prefer-to-be-defined.md) - suggest using
+  `toBeDefined()`.
 * [prefer-to-have-length](/docs/rules/prefer-to-have-length.md) - suggest using
   `toHaveLength()`.
 * [valid-expect](/docs/rules/valid-expect.md) - ensure expect is called
@@ -85,6 +88,7 @@ The rules enabled in this configuration are:
 * [jest/no-disabled-tests](/docs/rules/no-disabled-tests.md)
 * [jest/no-focused-tests](/docs/rules/no-focused-tests.md)
 * [jest/no-identical-title](/docs/rules/no-identical-title.md)
+* [jest/prefer-to-be-defined](/docs/rules/prefer-to-be-defined.md)
 * [jest/prefer-to-have-length](/docs/rules/prefer-to-have-length.md)
 * [jest/valid-expect](/docs/rules/valid-expect.md)
 

docs/rules/prefer-to-be-defined.md

@@ -0,0 +1,28 @@
+# Suggest using  `toBeDefined()` (prefer-to-be-defined)
+
+In order to have a better failure message, `toBeDefined()` should be used upon asserting expections on defined value.
+
+## Rule details
+
+This rule triggers a warning if `toBe()` is used to assert a undefined value.
+
+```js
+expect(true).not.toBe(undefined);
+```
+
+This rule is enabled by default.
+
+### Default configuration
+
+The following patterns are considered warning:
+
+```js
+expect(true).not.toBe(undefined);
+expect(true).not.toBeUndefined();
+```
+
+The following pattern is not warning:
+
+```js
+expect(true).toBeDefined();
+```

index.js

@@ -3,6 +3,7 @@
 const noDisabledTests = require('./rules/no_disabled_tests');
 const noFocusedTests = require('./rules/no_focused_tests');
 const noIdenticalTitle = require('./rules/no_identical_title');
+const preferToBeDefined = require('./rules/prefer_to_be_defined');
 const preferToHaveLength = require('./rules/prefer_to_have_length');
 const validExpect = require('./rules/valid_expect');
 
@@ -13,6 +14,7 @@ module.exports = {
         'jest/no-disabled-tests': 'warn',
         'jest/no-focused-tests': 'error',
         'jest/no-identical-title': 'error',
+        'jest/prefer-to-be-defined': 'warn',
         'jest/prefer-to-have-length': 'warn',
         'jest/valid-expect': 'error',
       },
@@ -45,6 +47,7 @@ module.exports = {
     'no-disabled-tests': noDisabledTests,
     'no-focused-tests': noFocusedTests,
     'no-identical-title': noIdenticalTitle,
+    'prefer-to-be-defined': preferToBeDefined,
     'prefer-to-have-length': preferToHaveLength,
     'valid-expect': validExpect,
   },

rules/__tests__/prefer_to_be_defined.test.js

@@ -0,0 +1,35 @@
+'use strict';
+
+const RuleTester = require('eslint').RuleTester;
+const { rules } = require('../../');
+
+const ruleTester = new RuleTester();
+
+ruleTester.run('prefer_to_be_defined', rules['prefer-to-be-defined'], {
+  valid: ['expect(true).toBeDefined();'],
+
+  invalid: [
+    {
+      code: 'expect(true).not.toBe(undefined);',
+      errors: [
+        {
+          message: 'Use toBeDefined() instead',
+          column: 14,
+          line: 1,
+        },
+      ],
+      output: 'expect(true).toBeDefined();',
+    },
+    {
+      code: 'expect(true).not.toBeUndefined();',
+      errors: [
+        {
+          message: 'Use toBeDefined() instead',
+          column: 14,
+          line: 1,
+        },
+      ],
+      output: 'expect(true).toBeDefined();',
+    },
+  ],
+});

rules/prefer_to_be_defined.js

@@ -0,0 +1,53 @@
+'use strict';
+
+module.exports = context => {
+  return {
+    CallExpression(node) {
+      const calleeName = node.callee.name;
+
+      if (
+        calleeName === 'expect' &&
+        node.arguments.length == 1 &&
+        node.parent &&
+        node.parent.type === 'MemberExpression' &&
+        node.parent.parent &&
+        node.parent.parent.type === 'MemberExpression'
+      ) {
+        const parentProperty = node.parent.property;
+        const propertyName = parentProperty.name;
+        const parentProperty2 = node.parent.parent.property;
+        const propertyName2 = parentProperty2.name;
+        const argument = node.parent.parent.parent.arguments[0];
+        const propertyDot = context
+          .getSourceCode()
+          .getFirstTokenBetween(
+            parentProperty,
+            parentProperty2,
+            token => token.value === '.'
+          );
+        if (
+          (propertyName === 'not' &&
+            propertyName2 === 'toBe' &&
+            argument.value === undefined) ||
+          (propertyName === 'not' && propertyName2 === 'toBeUndefined')
+        ) {
+          context.report({
+            fix(fixer) {
+              const fixes = [
+                fixer.remove(parentProperty),
+                fixer.remove(propertyDot),
+                fixer.replaceText(parentProperty2, 'toBeDefined'),
+              ];
+              if (argument) {
+                fixes.push(fixer.remove(argument));
+              }
+              return fixes;
+            },
+            message: 'Use toBeDefined() instead',
+            node: parentProperty,
+          });
+        }
+      }
+    },
+  };
+};