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Configuration

Intern is configured with a standard JavaScript object. This object may contain properties applicable to either environment that Intern can run in (Node or browser). Config properties may be set via a file, the command line, browser query args, or an environment variable. All of these methods use the same basic syntax and provide the same capabilities. Assuming Intern is being run with the default Node runner or browser runner and without a config argument, Intern will attempt to load configuration informatioon from an intern.json file in the project root.

Wherever config property values come from, the executor will validate and normalize them into a canonical format ("resolve" them) when the testing process starts. This allows the executor’s constructor or configure method to be flexible in what data it accepts. For example, the canonical form of the environments property is an array of objects:

environments: [{ browserName: 'chrome' }];

However, Intern will accept a simple string for the environments property and will expand it into an array of a single object where the browserName property is the given string.

Schema

Intern includes a JSON schema for its config format. This schema describes all the properties that might be included in an intern.json config file, and includes help text for each property.

To use the schema with an editor such as VS Code, add a $schema property to your intern.json file that points to the schema, like:

{
  "$schema": "./node_modules/intern/schemas/config.json"
}

Environment-specific config

Tests can run in two basic environments: Node and browsers. By default, “resource” properties (suites, plugins, reporters, and loader) in a config file apply to both environments. This means that if the same config is used to run tests in a browser and in Node, the same resources will be loaded in both environments. In some cases this isn’t desirable because tests may load application code that depends on environment-specific properties or features, such as the DOM. Intern’s config provides node and browser properties for this use case. These properties specify resources that will only be loaded in the given environment. The values in these properties will be shallowly mixed into the base config rather than replacing it.

⚠️ Note that this is different than the mode property in Intern 3, which had values of “client” or “runner”. Intern 3’s mode indicated whether tests were being run in unit test or functional test mode, but it was sometimes used as an environment check due to the fact that functional tests always run in Node.

Properties

A number of config properties are applicable whether Intern is running in Node or directly in a browser. Some of the more common ones are listed below.

💡 See the API docs for a complete list of the available config properties.

Property Description Default
bail When true, stop testing after the first failure false
baseline When true, run benchmark tests in baseline mode false
benchmark When true, run benchmark tests (if loaded) false
debug If true, display runtime messages to the console false
defaultTimeout The time, in ms, before an async test times out 30000
filterErrorStack If true, filter non-application code lines out of stack traces false
grep Regular expression used to filter which suites and tests are run /.*/
loader An optional loader script and options { script: 'default' }
plugins A list of Intern extensions to load before tests begin []
reporters A list of reporters to use []
suites A list of suite paths or globs to load unit tests from []
warnOnUnhandledRejection If true or a regex matching a unhandled rejection, emit a warning instead of an error undefined
warnOnUncaughtException If true or a regex matching an uncaught error, emit a warning instead of an error undefined

Some properties are only meaningful for Node or WebDriver tests:

Property Description Default
capabilities Default capabilities to be used for WebDriver sessions { 'idle-timeout': 60 }
coverage An array of paths or globs to collect coverage data for []
environments Browser + OS combinations to be tested using WebDriver []
functionalRetries rerun failed sessions when at least one other session succeeds 0
functionalSuites Suites to run in WebDriver mode []
functionalTimeouts Timeouts used in functional tests { connectTimeout: 30000 }
leaveRemoteOpen If true, leave remote browsers open after testing has finished false
maxConcurrency The maximum number of sessions to drive concurrently Infinity
serveOnly When true, Intern will start its instrumenting web server but not run tests false
serverPort The port the instrumenting server should listen on 9000
serverUrl A URL a remote executor can use to reach the local Intern http://localhost:9000
tsconfig Optional path to a tsconfig.json for ts-node. Uses the project's by default. Set to false to explicitly prevent registering tsnode in projects with TypeScript ``
tunnel The name of a tunnel to use for WebDriver tests selenium
tunnelOptions Options to use for the WebDriver tunnel { tunnelId: Date.now() }

The environment-specific properties come into play when Intern is running in that environment:

Property Description Default
browser Resources (loader, plugins, reporters, suites) that only apply to browser tests {}
node Resources (loader, plugins, reporters, suites, tsconfig) that only apply to Node tests {}

There are also several properties that are handled by the config file processing system that aren’t directly involved in the testing process. These properties are ignored if set programmatically.

Property Description
description A short string describing a test config
extends Another config or config file that the config extends
help Display a help message
showConfig When true, show the resolved configuration and exit
showConfigs When true, show information about the currently loaded config file

Suite glob expressions

Suites may be specified as file paths or using glob expressions. Globbing is handled with the glob Node package.

{
  suites: ['tests/unit/**/*.js', 'tests/integration/foo.js']
}

Intern also understands glob-based exclusion using the ! modifier:

{
  suites: ['tests/**/*.js', '!tests/functional/**']
}

Note that using globs with the browser client requires that Intern’s own server be used to serve test suites. This is because the browser client on its own has no way to resolve file system globs; it passes the to the Intern server running on Node, which resolves them and returns list of file paths.

extends

If the extends property is set in a base config, it must be the path to a different config file. At run time, the properties from the config file with the extends value will be mixed into the properties from the config file being extended.

If the extends property is set in a child config, it must be the name of a different child config within the same config file, or an array of such names. When a child config extends multiple other child configs, properties from the right-most config being extended will override properties from configs to the left.

{
  configs: {
    a: {
      /* ... */
    },
    b: {
      /* ... */
    },
    c: {
      /* ... */
    },
    d: {
      extends: ['a', 'c']
      /* ... */
    }
  }
}

Given the config above, and assuming child config “d” is selected, the following resolution process will occur:

  1. Child “c” will be mixed into child “a”
  2. Child “d” will be mixed into the result of 1
  3. The result of 2 will be mixed into the base config
  4. The result of 3 will be the resolved config

Displaying config information

Intern has two config properties that can be used to display configuration information: showConfig and showConfigs.

showConfig

Setting the showConfig property to true will cause Intern to dump the resolved configuration to the current environment’s console.

$ npx intern showConfig
{
    "bail": false,
    "baseline": false,
    "benchmark": false,
    "reporters": [
        {
            "name": "console"
        }
    ]
}

showConfigs

Setting the showConfigs property to true will cause Intern to show information about a given config file. Intern will print the value of the current config file’s description property, and then list all child configs contained in the config file. For example, with a config file containing the following data:

{
  description: 'Default test suite',
  configs: {
    webdriver: {
      description: 'Run webdriver tests'
    },
    ci: {
      description: 'Run tests on a CI server'
    }
  }
}

running Intern with the showConfigs property set would display the following text:

$ npx intern showConfigs
Default test suite

Configs:
  webdriver  (Run webdriver tests)
  ci         (Run tests on a CI server)

Config structure

The config structure is a simple JSON object, so all of its property values must be serializable (RegExp objects are serialized to strings).

{
  // General properties
  bail: false,
  baseline: false,
  suites: ['tests/unit/*.js'],

  // Browser and node specific resources
  browser: {
    suites: ['tests/unit/dom_stuff.js']
  },
  node: {
    suites: ['tests/unit/dom_stuff.js']
  },

  configs: {
    // Child configs have the same structure as the main config
    ci: {
      bail: true,
      'suites+': ['tests/unit/other.js']
    }
  }
}

There are four general sections to a config:

  • General properties: this includes everything but "browser", "configs", and "node"
  • Node-specific resources: resource properties ("loader", "plugins", "reporters", "suites") that apply only to Node environments.
  • Browser-specific resources: resource properties ("loader", "plugins", "reporters", "suites") that apply only to browser environments.
  • Child configs: named configs in the "configs" object; each of these can have any config properties except "configs" (i.e., general properties, Node resources, and browser resources).

Sources of configuration information

Intern takes in configuration data from several sources. In order of increasing precedence, they are:

  1. Config file
  2. Environment variable
  3. Command line or query args
  4. Programmatically

Multiple configuration methods may be used during a single run of Intern. The configuration will be fully resolved before tests are executed.

Config File

An Intern config file is a JSON file specifying config properties, for example:

{
  environments: [{ browserName: 'chrome' }],
  suites: ['tests/unit/all.js']
}

By default, intern will try to load a file named intern.json from the project root directory. A different config file can be specified by passing a config property to the Node or browser runners.

A child config can be selected by adding @<child> to the config file name. For example, to load a child config named “ci” from the default config file, you could run:

$ npx intern config=@ci

To load a config named “remote” from a config file named “intern-local.json”, run:

$ npx intern config=intern-local.json@remote

Environment variable

In a Node environment, Intern may be configured using an INTERN_ARGS environment variable. This variable is treated just like a string of command line arguments. For example, these two executions of Intern are equivalent:

$ npx intern grep='run.*' suites=
export INTERN_ARGS="grep=run.* suites="
$ npx intern

Command line

Config properties may be provided directly on the command line when starting Intern. Properties must be specified using property=value syntax. For example,

$ npx intern grep='run.*' suites=

Object values may be input as serialized strings (e.g., environments='{"browserName":"chrome"}'). Array values may be set by repeating a property (e.g., suites="foo.js" suites="bar.js").

Query args

Query args work very similarly to command line args. They have the same format, but with URL query arg separators, and escaping of special characters as necessary.

http://localhost:8080/node_modules/intern/?grep=run.*&suites=

Programmatically

When creating an executor programmatically it may be configured via its constructor, and/or via its configure method.

const intern = new Node({ grep: /run.*/, suites: [] });

or

intern.configure({ grep: /run.*/, suites: [] });

The configure method may be called any number of times before the testing process is started.

Configuring loaders

Intern uses loader scripts to communicate with various loaders so test suites of any module format may be used. Loader scripts are simply standalone scripts (like plugins) that connect Intern with a loader. Intern has a number of loader scripts available to help it work with popular loaders and formats. If no loader script is defined, then Intern will use the default loader script for the environment (CommonJS in Node and <script> tag injection in the browser).

To use one of Intern's pre-defined loader scripts, simply specify it's name. The loader script will expect the loader package to be installed in node_modules using NPM.

{
  browser: {
    loader: 'dojo'
  }
}

Additional options may be provided through the options parameter. These options are passed through to the registered loader script.

{
  browser: {
    loader: {
      script: './support/my/custom/loader.js',
      options: { basePath: '_build' }
    }
  }
}

It's useful to think of Intern's loader scriptss as glue code that Intern uses to load configured suites within the environment. When Intern needs to load a module (i.e. a test suite) it hands off a list of these modules to the loader script and waits for the loading process to be handled by the loader. For more information and options look at the loader scripts in the Intern repository.

Configuring plugins

Plugins are standalone scripts or modules that are loaded by Intern. Standalone plugins (ones that do not require a loader) are ran in-order early in the Intern lifecycle before practically anything else. This is to allow plugins a chance to listen to Intern events and augment the environment as early as possible. Module plugins have a useLoader property and are loaded later in Intern's lifecycle with the configured loader. Any number of plugins may be added to Intern.

{
  plugins: [
    'node_modules/babel-register/lib/node.js',
    {
      script: 'tests/support/mongodbAccess.js',
      options: { dbUrl: 'https://testdb.local' }
    },
    {
      script: 'tests/support/dojoMocking.js',
      useLoader: true
    }
  ]
}

Similar to loader scripts, plugin configurations with options are passed to the plugin when it is registered with Intern.

Configuration resolution

At runtime, the environment-specific resources and any active child configs will be mixed into the resolved config. In general, properties from more specific sources will override properties from lower precedence sources. The order of precedence, from lowest to highest, is:

  1. A config being extended by the current config
  2. The current config
  3. An active child config in the current config

There are a few exceptions:

  1. The "node" and "browser" properties in a child config are shallowly mixed into "node" and "browser" in the base config. For example, if "node" in the base config looks like: 
    "node": {
    "suites": [ "tests/unit/foo.js" ],
    "plugins": [ "tests/plugins/bar.js" ]
}
    and "node" in a child config looks like: 
    "node": {
    "suites": [ "tests/unit/baz.js" ],
}
    then the value of node in the resolved config (assuming the child config is active) will be: 
    "node": {
    // node.suites from the child overrides node.suites from the base config
    "suites": [ "tests/unit/baz.js" ],
    // node.plugins from the base config remains
    "plugins": [ "tests/plugins/bar.js" ]
}
  2. Resource arrays in "node" or "browser" ("plugins", "reporters", "suites"), are added to the corresponding resource arrays in the base config. For example, if the base config has: 
    "suites": [ "tests/unit/foo.js" ]
    and the "node" section has: 
    "suites": [ "tests/unit/bar.js" ]
    both sets of suites will be loaded when running on Node.
  3. Some properties can be extended (rather than replaced) by adding a '+' to the property name. For example, if the base config has: 
    "suites": [ "tests/unit/foo.js" ]
    and a child config has: 
    "suites+": [ "tests/unit/bar.js" ]
    the resolved value of suites will be: 
    "suites": [ "tests/unit/foo.js", "tests/unit/bar.js" ]
    Extendable properties are resources (suites, plugins, reporters), instrumenterOptions, tunnelOptions, and capabilities.