Through this project I sought to deepen my experience in component testing and to discover Jest, a JavaScript testing framework.

The 'Capital City Finder' program accepts a state (country or region) as an argument and returns the corresponding capital city. The program must be extensive, covering every United Nations–⁠recognised country, in addition to many regions, e.g., the capital of the Dutch province of South Holland is Rotterdam.

Unlike other programming languages, JavaScript cannot create associative arrays, however the same functionality may be achieved using objects. In this case, the object cityFinder is defined with an object literal of state–capital (property–value) pairs, eg. "Republic of the Congo": "Brazzaville". The following function accesses the cityFinder object and, should the argument match a property, returns the property's value:

function returnCapital(state) {
    return cityFinder[state];
}

Thus, supplying the input Malaysia returns the value Kuala Lumpur. The combination of the cityFinder object and the returnCapital(state) function may be thought of collectively as the capital finder module.

To ensure the extensiveness of the capital finder module (i.e. app.js file) test data should cover a collection of geographically and culturally disparate states. This approach aknowledges the risk of a particular cultural bias, especially a pro-Occidental or a pro-Anglo-Saxon one, during development resulting in a disregard for dissimilar countries. For this reason, it is advantageous that each test condition concern one of the six inhabited continents: Africa, Asia, Europe, North America, South America and Oceania.

Jest is an open-source library that simplifies performing tests in JavaScript. In this project Jest is installed and the test script of package.json is set to "jest" so that Jest runs when npm test is entered in the command line. The statement module.exports = returnCapital exports the function to be tested from the app.js file. The function is then imported into the newly created app.test.js file via const returnCapital = require('./app'). The Jest method test('', () => {expect().toBe()}) verifies expected output against actual output for a given input.

Project Name: Capital City Finder
Created By: Ainsley
Creation Date: 21/01/20
Test Condition ID: Af
Test Condition Description: Verify that the program returns the correct capital city for a given African country or province.

Test Condition ID: As
Test Condition Description: Verify that the program returns the correct capital city for a given Asian country or province.

Test Condition ID: Eu
Test Condition Description: Verify that the program returns the correct capital city for a given European country or province.

Test Condition ID: No
Test Condition Description: Verify that the program returns the correct capital city for a given North American country or province.

Test Condition ID: So
Test Condition Description: Verify that the program returns the correct capital city for a given South American country or province.

Test Condition ID: Oc
Test Condition Description: Verify that the program returns the correct capital city for a given Oceanian country or province.