Add test to catch missing version updates.

plugins/woocommerce-admin/tests/plugin-version.php

@@ -0,0 +1,34 @@
+<?php
+/**
+ * Plugin Version Tests
+ *
+ * @package WooCommerce\Tests\Reports
+ * @since 3.6.4
+ */
+
+/**
+ * Plugin Version Tests Class
+ *
+ * @package WooCommerce\Tests\Reports
+ * @since 3.6.4
+ */
+class WC_Admin_Tests_Plugin_Version extends WP_UnitTestCase {
+	/**
+	 * Ensure that all version numbers match.
+	 */
+	public function test_version_numbers() {
+		// Get package.json version.
+		$package_json = file_get_contents( 'package.json' );
+		$package      = json_decode( $package_json );
+
+		// Get main plugin file header version.
+		$plugin = get_file_data( 'woocommerce-admin.php', array( 'Version' => 'Version' ) );
+
+		// Get plugin DB version.
+		$db_version = defined( 'WC_ADMIN_VERSION_NUMBER' ) ? constant( 'WC_ADMIN_VERSION_NUMBER' ) : false;
+
+		// Compare all versions to the package.json value.
+		$this->assertEquals( $package->version, $plugin['Version'], 'Plugin header version does not match package.json' );
+		$this->assertEquals( $package->version, $db_version, 'DB version constant does not match package.json' );
+	}
+}