test: add tests for Autosize constructor and properties

PR-URL: #9485
Co-authored-by: Athan Reines <kgryte@gmail.com>
Reviewed-by: Athan Reines <kgryte@gmail.com> 
Co-authored-by: stdlib-bot <noreply@stdlib.io>

Author: 3 people

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

@@ -0,0 +1,132 @@
+/**
+* @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 isString = require( '@stdlib/assert/is-string' ).isPrimitive;
+var Autosize = require( './../lib' );
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+	t.ok( true, __filename );
+	t.strictEqual( typeof Autosize, 'function', 'main export is a function' );
+	t.end();
+});
+
+tape( 'the constructor returns an instance which has a `contains` property', function test( t ) {
+	var v = new Autosize();
+	t.strictEqual( hasOwnProp( v, 'contains' ), false, 'returns expected value' );
+	t.strictEqual( hasProp( v, 'contains' ), true, 'returns expected value' );
+	t.strictEqual( isString( v.contains ), true, 'returns expected value' );
+	t.end();
+});
+
+tape( 'the constructor returns an instance having a `contains` property which throws an error if set to an invalid value', function test( t ) {
+	var values;
+	var i;
+
+	values = [
+		'beep',
+		'boop',
+		'invalid',
+		'CONTENT',
+		'PADDING',
+		5,
+		NaN,
+		null,
+		void 0,
+		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 autosize = new Autosize();
+			autosize.contains = value;
+		};
+	}
+});
+
+tape( 'the constructor returns an instance having a `contains` property which returns the method for determining how a size calculation should be performed', function test( t ) {
+	var autosize = new Autosize();
+	t.strictEqual( autosize.contains, 'content', 'returns expected value' );
+
+	autosize = new Autosize({
+		'contains': 'padding'
+	});
+	t.strictEqual( autosize.contains, 'padding', 'returns expected value' );
+
+	autosize = new Autosize({
+		'contains': 'content'
+	});
+	t.strictEqual( autosize.contains, 'content', 'returns expected value' );
+
+	t.end();
+});
+
+tape( 'the constructor returns an instance having a `contains` property which can be set to a valid method', function test( t ) {
+	var autosize = new Autosize();
+
+	autosize.contains = 'padding';
+	t.strictEqual( autosize.contains, 'padding', 'returns expected value' );
+
+	autosize.contains = 'content';
+	t.strictEqual( autosize.contains, 'content', 'returns expected value' );
+
+	t.end();
+});
+
+tape( 'the constructor returns an instance which emits an event when the `contains` property is set to a new value', function test( t ) {
+	var autosize;
+	var count;
+
+	autosize = new Autosize();
+	count = 0;
+
+	autosize.on( 'change', onChange );
+
+	autosize.contains = 'padding';
+	t.strictEqual( count, 1, 'returns expected value' );
+
+	autosize.contains = 'content';
+	t.strictEqual( count, 2, 'returns expected value' );
+
+	// Setting to the same value should not emit an event:
+	autosize.contains = 'content';
+	t.strictEqual( count, 2, 'returns expected value' );
+
+	t.end();
+
+	function onChange() {
+		count += 1;
+	}
+});