eslint-plugin-chai-expect

ESLint plugin that checks for common chai.js expect() mistakes

[!IMPORTANT] The recommended preset is for the ESLint legacy configuration system (.eslintrc.json). The recommended-flat configuration is for the new flat configuration system.

Requirements

• Node.js 20 or above
• ESLint 2.x to 10.x

Installation

npm install --save-dev eslint-plugin-chai-expect

Configuration

Legacy ESLint Configuration Format (.eslintrc.json)

Add a plugins section and specify chai-expect as a plugin:

{
  "plugins": [
    "chai-expect"
  ]
}

Enable the rules that you would like to use:

{
  "rules": {
    "chai-expect/no-inner-compare": 2,
    "chai-expect/no-inner-literal": 2,
    "chai-expect/missing-assertion": 2,
    "chai-expect/terminating-properties": 2
  }
}

Or, if you just want the above defaults, you can avoid all of the above and just extend the config:

{
  "extends": ["plugin:chai-expect/recommended"]
}

Flat ESLint Configuration Format (eslint.config.js)

Add a plugins section and specify chai-expect as a plugin and enable the rules that you would like to use:

import chaiExpectPlugin from 'eslint-plugin-chai-expect';

export default [
  {
    "plugins": {
      "chai-expect": chaiExpectPlugin
    },
    "rules": {
      "chai-expect/no-inner-compare": 2,
      "chai-expect/no-inner-literal": 2,
      "chai-expect/missing-assertion": 2,
      "chai-expect/terminating-properties": 2,
      "chai-expect/no-uncalled-method": 2
    }
  }
];

Or, if you just want the above defaults, you can avoid all of the above and just extend the config:

import chaiExpectPlugin from 'eslint-plugin-chai-expect';

export default [
  chaiExpectPlugin.configs["recommended-flat"],
  {
    // ...
  },
];

Rules

• no-inner-compare - Prevent using comparisons in the expect() argument
• no-inner-literal - Prevent using literals in the expect() argument (undefined, null, NaN, (+|-)Infinity, this, booleans, numbers, strings, and BigInt or regex literals)
• missing-assertion - Prevent calling expect(...) without an assertion like .to.be.ok
• terminating-properties - Prevent calling to.be.ok and other assertion properties as functions
• no-uncalled-method - Prevent using to.throw and other assertion methods as properties without calling them

Additional configuration

terminating-properties rule

A number of extensions to chai add additional terminating properties. For example chai-http adds:

• headers
• html
• ip
• json
• redirect
• text

The terminating-properties rule can be configured to ensure these (or other) additional properties are not used as functions:

{
  "rules": {
    "chai-expect/terminating-properties": ["error", {
      "properties": ["headers", "html", "ip", "json", "redirect", "test"]
    }]
  }
}

no-uncalled-method rule

By default, this rule checks for throw, throws, and Throw. You can configure additional methods that should not be used as properties:

{
  "rules": {
    "chai-expect/no-uncalled-method": ["error", {
      "methods": ["include", "satisfy", "respondTo"]
    }]
  }
}

License

eslint-plugin-chai-expect is licensed under the MIT License.