woocommerce/tests/unit-tests/cart-functions.php

<?php
/**
 * Test WC cart functions
 *
 * @since 2.3.0
 */
class WC_Tests_Cart_Functions extends WC_Unit_Test_Case {

	/**
	 * Test wc_empty_cart()
	 *
	 * @since 2.3.0
	 */
	public function test_wc_empty_cart() {
		// Create dummy product
		$product = WC_Helper_Product::create_simple_product();

		// Add the product to the cart
		WC()->cart->add_to_cart( $product->id, 1 );

		// Empty the cart
		wc_empty_cart();

		// Check if the cart is empty
		$this->assertEquals( 0, WC()->cart->get_cart_contents_count() );

		// Delete the previously created product
		WC_Helper_Product::delete_product( $product->id );
	}
}