Add date predicate (#26)

source/index.ts

@@ -4,6 +4,7 @@ import {StringPredicate} from './lib/predicates/string';
 import {NumberPredicate} from './lib/predicates/number';
 import {BooleanPredicate} from './lib/predicates/boolean';
 import {ArrayPredicate} from './lib/predicates/array';
+import {DatePredicate} from './lib/predicates/date';
 
 export interface Ow {
 	(value: any, predicate: Predicate): void;
@@ -23,6 +24,10 @@ export interface Ow {
 	 * Test the value to be an array.
 	 */
 	array: ArrayPredicate;
+	/**
+	 * Test the value to be a Date.
+	 */
+	date: DatePredicate;
 }
 
 const main = (value: any, predicate: Predicate) => {
@@ -46,6 +51,9 @@ Object.defineProperties(main, {
 	},
 	array: {
 		get: () => new ArrayPredicate()
+	},
+	date: {
+		get: () => new DatePredicate()
 	}
 });
 

source/lib/predicates/date.ts

@@ -0,0 +1,31 @@
+import {Predicate, Context} from './predicate';
+
+export class DatePredicate extends Predicate<Date> {
+	constructor(context?: Context) {
+		super('date', context);
+	}
+
+	/**
+	 * Test a date to be before another date.
+	 *
+	 * @param date Maximum value.
+	 */
+	before(date: Date) {
+		return this.addValidator({
+			message: value => `Expected ${value.toISOString()} to be before ${date.toISOString()}`,
+			validator: value => value.getTime() < date.getTime()
+		});
+	}
+
+	/**
+	 * Test a date to be before another date.
+	 *
+	 * @param date Minimum value.
+	 */
+	after(date: Date) {
+		return this.addValidator({
+			message: value => `Expected ${value.toISOString()} to be after ${date.toISOString()}`,
+			validator: value => value.getTime() > date.getTime()
+		});
+	}
+}

source/test/date.ts

@@ -0,0 +1,19 @@
+import test from 'ava';
+import m from '..';
+
+test('date', t => {
+	t.notThrows(() => m(new Date(), m.date));
+	t.throws(() => m('12', m.date), 'Expected argument to be of type `date` but received type `string`');
+});
+
+test('date.before', t => {
+	t.notThrows(() => m(new Date('2017-11-25'), m.date.before(new Date('2017-11-26'))));
+	t.notThrows(() => m(new Date('2017-11-25T12:00:00Z'), m.date.before(new Date('2017-11-25T12:00:01Z'))));
+	t.throws(() => m(new Date('2017-11-25T12:00:00Z'), m.date.before(new Date('2017-11-25T12:00:00Z'))), 'Expected 2017-11-25T12:00:00.000Z to be before 2017-11-25T12:00:00.000Z');
+});
+
+test('date.after', t => {
+	t.notThrows(() => m(new Date('2017-11-26'), m.date.after(new Date('2017-11-25'))));
+	t.notThrows(() => m(new Date('2017-11-26T12:00:00Z'), m.date.after(new Date('2017-11-26T11:59:59Z'))));
+	t.throws(() => m(new Date('2017-11-26T12:00:00Z'), m.date.after(new Date('2017-11-26T12:00:00Z'))), 'Expected 2017-11-26T12:00:00.000Z to be after 2017-11-26T12:00:00.000Z');
+});