test: add tests for Padding constructor and properties

PR-URL: #10251
Co-authored-by: Athan Reines <kgryte@gmail.com>
Reviewed-by: Athan Reines <kgryte@gmail.com> 
Reviewed-by: Gururaj Gurram <gururajgurram1512@gmail.com>

Author: Sachinn-64

lib/node_modules/@stdlib/plot/vega/autosize/ctor/test/test.js

@@ -248,7 +248,7 @@ tape( 'the `toJSON` method is implicitly invoked by `JSON.stringify`', function
 	t.end();
 });
 
-tape( 'the constructor returns an instance which an EventEmitter', function test( t ) {
+tape( 'the constructor returns an instance which is an EventEmitter', function test( t ) {
 	var autosize = new Autosize();
 	t.strictEqual( instanceOf( autosize, EventEmitter ), true, 'returns expected value' );
 	t.end();

lib/node_modules/@stdlib/plot/vega/padding/ctor/test/test.bottom.js

@@ -0,0 +1,133 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var tape = require( 'tape' );
+var hasOwnProp = require( '@stdlib/assert/has-own-property' );
+var hasProp = require( '@stdlib/assert/has-property' );
+var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
+var Padding = require( './../lib' );
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+	t.ok( true, __filename );
+	t.strictEqual( typeof Padding, 'function', 'main export is a function' );
+	t.end();
+});
+
+tape( 'the constructor returns an instance which has a `bottom` property', function test( t ) {
+	var v;
+
+	v = new Padding();
+	t.strictEqual( hasOwnProp( v, 'bottom' ), false, 'returns expected value' );
+	t.strictEqual( hasProp( v, 'bottom' ), true, 'returns expected value' );
+	t.strictEqual( isNumber( v.bottom ), true, 'returns expected value' );
+
+	t.end();
+});
+
+tape( 'the constructor returns an instance having a `bottom` property which throws an error if set to an invalid value', function test( t ) {
+	var values;
+	var i;
+
+	values = [
+		'beep',
+		'boop',
+		null,
+		true,
+		false,
+		[],
+		{},
+		function noop() {}
+	];
+	for ( i = 0; i < values.length; i++ ) {
+		t.throws( badValue( values[ i ] ), TypeError, 'throws an error when provided ' + values[ i ] );
+	}
+	t.end();
+
+	function badValue( value ) {
+		return function badValue() {
+			var padding = new Padding();
+			padding.bottom = value;
+		};
+	}
+});
+
+tape( 'the constructor returns an instance having a `bottom` property', function test( t ) {
+	var padding;
+
+	padding = new Padding();
+	t.strictEqual( padding.bottom, 0, 'returns expected value' );
+
+	padding = new Padding({
+		'bottom': 10
+	});
+	t.strictEqual( padding.bottom, 10, 'returns expected value' );
+
+	padding = new Padding({
+		'bottom': 20
+	});
+	t.strictEqual( padding.bottom, 20, 'returns expected value' );
+
+	t.end();
+});
+
+tape( 'the constructor returns an instance having a `bottom` property which can be set to a valid value', function test( t ) {
+	var padding;
+
+	padding = new Padding();
+
+	padding.bottom = 10;
+	t.strictEqual( padding.bottom, 10, 'returns expected value' );
+
+	padding.bottom = 20;
+	t.strictEqual( padding.bottom, 20, 'returns expected value' );
+
+	t.end();
+});
+
+tape( 'the constructor returns an instance which emits an event when the `bottom` property is set to a new value', function test( t ) {
+	var padding;
+	var count;
+
+	padding = new Padding();
+	count = 0;
+
+	padding.on( 'change', onChange );
+
+	padding.bottom = 10;
+	t.strictEqual( count, 1, 'returns expected value' );
+
+	padding.bottom = 20;
+	t.strictEqual( count, 2, 'returns expected value' );
+
+	// Setting to the same value should not emit an event:
+	padding.bottom = 20;
+	t.strictEqual( count, 2, 'returns expected value' );
+
+	t.end();
+
+	function onChange() {
+		count += 1;
+	}
+});