Split out utility functions, add tests

src/index.js

@@ -1,5 +1,5 @@
 const axios = require('axios');
-const moment = require('moment');
+const stringifyDates = require('./stringifyDates');
 
 class Forecast {
 	constructor({ accountId, token }) {
@@ -45,47 +45,4 @@ class Forecast {
 	}
 }
 
-function stringifyDates(options) {
-	const qs = {};
-
-	if (options.startDate) {
-		qs.start_date = toDateString(options.startDate);
-	}
-
-	if (options.endDate) {
-		qs.end_date = toDateString(options.endDate);
-	}
-
-	return qs;
-}
-
-function toDateString(obj) {
-	let date;
-
-	if (typeof obj === 'string') {
-		date = moment(obj);
-		if (!date.isValid()) {
-			throw new Error(
-				'Invalid date string; expecting ISO-8601 compatible format.'
-			);
-		}
-	} else if (obj instanceof Date) {
-		// Check for bad date objects like: new Date('LOL');
-		if (isNaN(+obj)) {
-			throw new Error('Invalid date object; expecting non NaN date value.');
-		}
-		date = moment(obj);
-	} else if (obj._isAMomentObject) {
-		date = obj;
-	}
-
-	if (!date) {
-		throw new Error(
-			'Invalid date; expecting a valid: ISO-8601 compatible date string, a Date object or a moment date object.'
-		);
-	}
-
-	return date.format('YYYY-MM-DD');
-}
-
 module.exports = Forecast;

src/stringifyDates.js

@@ -0,0 +1,13 @@
+const toDateString = require('./toDateString');
+
+module.exports = options => {
+	const qs = {};
+
+	if (options.startDate) qs.start_date = toDateString(options.startDate);
+
+	if (options.endDate) {
+		qs.end_date = toDateString(options.endDate);
+	}
+
+	return qs;
+};

src/stringifyDates.test.js

@@ -0,0 +1,28 @@
+const stringifyDates = require('./stringifyDates');
+
+// Mocks the toDateString function to always return
+// the input. It isn't the system under test in this
+// file.
+jest.mock('./toDateString', () => args => args);
+
+describe('stringifyDates', () => {
+	it('returns input as-is', () => {
+		expect(stringifyDates({})).toEqual({});
+	});
+
+	it('converts the start date', () => {
+		expect(stringifyDates({ startDate: 'someValue' })).toMatchObject({
+			start_date: 'someValue',
+		});
+	});
+
+	it('converts the end date', () => {
+		const output = stringifyDates({ endDate: 'someValue' });
+
+		expect(output).toMatchObject({
+			end_date: 'someValue',
+		});
+
+		expect(Object.keys(output).length).toBe(1);
+	});
+});

src/toDateString.js

@@ -0,0 +1,30 @@
+const moment = require('moment');
+
+module.exports = obj => {
+	let date;
+
+	if (typeof obj === 'string') {
+		date = moment(obj);
+		if (!date.isValid()) {
+			throw new Error(
+				'Invalid date string; expecting ISO-8601 compatible format.'
+			);
+		}
+	} else if (obj instanceof Date) {
+		// Check for bad date objects like: new Date('LOL');
+		if (isNaN(+obj)) {
+			throw new Error('Invalid date object; expecting non NaN date value.');
+		}
+		date = moment(obj);
+	} else if (obj && obj._isAMomentObject) {
+		date = obj;
+	}
+
+	if (!date) {
+		throw new Error(
+			'Invalid date; expecting a valid: ISO-8601 compatible date string, a Date object or a moment date object.'
+		);
+	}
+
+	return date.format('YYYY-MM-DD');
+};

src/toDateString.test.js

@@ -0,0 +1,47 @@
+const toDateString = require('./toDateString');
+
+describe('toDateString', () => {
+	it('throws without input', () => {
+		expect(() => toDateString()).toThrow(
+			'Invalid date; expecting a valid: ISO-8601 compatible date string, a Date object or a moment date object.'
+		);
+	});
+
+	it('throws on invalid string input', () => {
+		const warn = jest
+			.spyOn(global.console, 'warn')
+			.mockImplementation(() => {});
+
+		expect(() => toDateString('Invalid')).toThrow(
+			'Invalid date string; expecting ISO-8601 compatible format.'
+		);
+
+		// Moment deprecation warning
+		expect(warn).toHaveBeenCalled();
+	});
+
+	it('works on valid string input', () => {
+		expect(toDateString('01-31-2000')).toBe('2000-01-31');
+	});
+
+	it('throws on invalid Date input', () => {
+		expect(() => toDateString(new Date('Invalid'))).toThrow(
+			'Invalid date object; expecting non NaN date value.'
+		);
+	});
+
+	it('works on valid Date input', () => {
+		expect(toDateString(new Date('01-31-2000'))).toBe('2000-01-31');
+	});
+
+	it('accepts any moment-ish object', () => {
+		const input = {
+			_isAMomentObject: true,
+			format: jest.fn().mockReturnValue('mocked value'),
+		};
+
+		expect(toDateString(input)).toBe('mocked value');
+
+		expect(input.format).toHaveBeenCalledWith('YYYY-MM-DD');
+	});
+});