TypeScript Support

Vest is written fully in TypeScript, and as such, it provides extensive TypeScript support.

Suite Generics

The Suite's create function takes three optional generic types - FieldName, GroupName and Callback.

Name	Type	Optional?	Default	Description
FieldName	string	Yes	string	A union of the allowed field names in the suite. This type is propagated to all the suite and suite response methods.
GroupName	string	Yes	string	A union of the allowed group names in the suite. This type is propagated to all the suite and suite response methods.
Callback	Function	Yes	Function	The type for the suite callback. This type is propagated into the suite callback, and can be used to defined the shape of the data for the suite callback.

import { create } from 'vest';

type FieldName = 'username' | 'password';
type GroupName = 'SignIn' | 'ChangePassword';
type Callback = (data: { username: string; password: string }) => void;

const suite = create<FieldName, GroupName, Callback>(data => {
  // data is now typed
  // ...
});

const res = suite();

res.getErrors('username');
res.getErrors('full_name'); // 🚨 Throws a compilation error

The following methods are typed:

• getError
• getErrors
• getErrorsByGroup
• getWarning
• getWarnings
• getWarningsByGroup
• hasErrors
• hasErrorsByGroup
• hasWarnings
• hasWarningsByGroup
• isValid
• isValidByGroup
• res.done
• suite.get

Typing Runtime Functions

The types mentioned above are useful, but they are not as strict, and only provides partial safety, as they only deal with the result object and not with the suite's operation.

The following functions can make use of the suite's types as well:

• group
• include
• omitWhen
• only
• optional
• skip
• skipWhen
• test

To do so, you can type your suite as mentioned in the previous section, and destruct these from directly from the suite.

import { create } from 'vest';

type TData = { username: string; password: string };
type FieldName = keyof TData;
type GroupName = 'SignIn' | 'ChangePassword';
type Callback = (data: TData) => void;

const suite = create<FieldName, GroupName, Callback>(data => {
  only('username');

  test('username', 'Password is required', () => {
    /*...*/
  }); // ✅
  test('password', 'Password is too required', () => {
    /*...*/
  }); // ✅

  test('confirm', 'Passwords do not match', () => {
    /*...*/
  }); // 🚨 Will throw a compilation error
});

const { test, group, only } = suite;

Exported Types

Vest exports the following types so you can use them to annotate your functions and variables:

• Suite<FieldName, GroupName, Callback>
  A single suite instance.

• SuiteRunResult<FieldName, GroupName>
  The immediate output of a suite invocation - suite(), including the done() function.

• SuiteResult<FieldName, GroupName>
  Non-actionable suite result, meaning - the same as SuiteRunResult, but without the done() function. The return type of suite.get().

• SuiteSummary<FieldName, GroupName>
  The static suite summary, all test results defined in the result object.

• IsolateTest<FieldName, GroupName>
  Rperesents a Vest test.

Custom Enforce Rules

See Custom Rule Typescript Support;