Merge pull request #31 from dreamit-de/9-exit-function

#9 Add ExitFunction type and doNotExitFunction

Author: sgohlke

README.md

@@ -1,6 +1,6 @@
 # funpara
 
-Function parameter library to ease development and testing. The library provides Date and Fetch related functions that can be used without complicated spy/mock setups so that an application can easily be tested with function parameters.
+Function parameter library to ease development and testing. The library provides Date, Exit and Fetch related functions that can be used without complicated spy/mock setups so that an application can easily be tested with function parameters.
 
 ## Installation
 
@@ -61,6 +61,7 @@ In **tests/index.test.ts** there are additional examples how the available code
 ### Types
 
 -   **DateFunction**: Type for a function that returns a Date.
+-   **ExitFunction**: Type for a function that given an exit code does not return anything.
 -   **FetchFunction**: Type for a fetch function that given an input (url, request, etc.) and request init returns a Promise<Response>
 
 ### Core functions
@@ -69,6 +70,7 @@ The following core functions can be used to create a new function or create dyna
 
 -   **nowDateFunction**: Returns a DateFunction that returns the current date.
 -   **fixedDateFunction**: Returns a DateFunction that returns a fixed date that matches the given date string.
+-   **doNotExitFunction**: Exit function that does not exit the process but throws an error instead.
 -   **fixedResponseFetchFunction**: Returns a FetchFunction that always returns a fixed response that matches the given body init and response init values.
 
 ### Fixed value functions

package.json

@@ -1,6 +1,6 @@
 {
     "name": "@dreamit/funpara",
-    "version": "1.0.1",
+    "version": "1.1.0",
     "description": "Function parameter library for coding and testing",
     "scripts": {
         "build": "tsup-node",

src/index.ts

@@ -99,3 +99,23 @@ export const timeoutFetchFunction: FetchFunction = (): Promise<Response> =>
     new Promise<Response>(() => {
         throw new Error('Connection failed ETIMEDOUT')
     })
+
+// Exit function related types and functions
+
+/**
+ * Type for a function that given an exit does not return anything.
+ * @param {number} code The exit code to use
+ * @returns {never} Does not return anything, may e.g. exit the process or throw an error
+ */
+export type ExitFunction = (code: number) => never
+
+/**
+ * Exit function that does not exit the process but throws an error instead
+ * Can be used in testing to avoid the tests exiting the application.
+ * @param {number} code The exit code to be thrown in the error
+ * @returns {never} Does not return anything but throws an error with the message
+ * "Exit function was called with code CODE" where CODE is the given code.
+ */
+export const doNotExitFunction: ExitFunction = (code: number): never => {
+    throw new Error(`Exit function was called with code ${code}`)
+}

tests/index.test.ts

@@ -1,6 +1,7 @@
 import type { DateFunction, FetchFunction } from '@/index'
 import {
     brokenJSONFetchFunction,
+    doNotExitFunction,
     fixedDateFunction,
     fixedResponseFetchFunction,
     notFoundFetchFunction,
@@ -159,3 +160,10 @@ test('Test fetch functions', async () => {
         data: { message: 'Error: Content-Type is not application/json' },
     })
 })
+
+test('Test exit functions', () => {
+    // Test that doNotExitFunction does not exit and returns the correct error message
+    expect(() => doNotExitFunction(1)).toThrow(
+        'Exit function was called with code 1',
+    )
+})