Add test for #17939 bug

phpunit.xml.dist

@@ -30,6 +30,9 @@
 		<testsuite name="comment-likes">
 			<directory prefix="test" suffix=".php">tests/php/modules/comment-likes</directory>
 		</testsuite>
+		<testsuite name="calypsoify">
+			<directory prefix="test" suffix=".php">tests/php/modules/calypsoify</directory>
+		</testsuite>
 		<testsuite name="likes">
 			<directory prefix="test_" suffix=".php">tests/php/modules/likes</directory>
 		</testsuite>

tests/php/modules/calypsoify/test-class.jetpack-calypsoify.php

@@ -0,0 +1,37 @@
+<?php
+/**
+ * Class Calypsoify.
+ *
+ * @package Jetpack
+ */
+
+require_jetpack_file( 'modules/calypsoify/class.jetpack-calypsoify.php' );
+
+/**
+ * Class WP_Test_Jetpack_Calypsoify
+ */
+class WP_Test_Jetpack_Calypsoify extends WP_UnitTestCase {
+
+	/**
+	 * Sets up each test.
+	 *
+	 * @inheritDoc
+	 */
+	public function setUp() {
+		parent::setUp();
+		$this->instance = Jetpack_Calypsoify::getInstance();
+	}
+
+	/**
+	 * Sets up the Masterbar mock.
+	 *
+	 * For sites when Masterbar is not active, we mock it. This test confirms that functions.
+	 *
+	 * @covers Jetpack_Calypsoify::mock_masterbar_activation
+	 * @see https://github.com/Automattic/jetpack/pull/17939
+	 */
+	public function test_mock_masterbar_activation() {
+		$this->instance->mock_masterbar_activation();
+		$this->assertTrue( class_exists( '\Automattic\Jetpack\Dashboard_Customizations\Masterbar' ) );
+	}
+}