New invoice tests

Author: fracz

src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java

@@ -36,6 +36,22 @@ public void testEmptyInvoiceHasEmptyTotal() {
         Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getTotal()));
     }
 
+    @Test
+    public void testInvoiceSubtotalWithTwoDifferentProducts() {
+        Product onions = new TaxFreeProduct("Warzywa", new BigDecimal("10"));
+        Product apples = new TaxFreeProduct("Owoce", new BigDecimal("10"));
+        invoice.addProduct(onions);
+        invoice.addProduct(apples);
+        Assert.assertThat(new BigDecimal("20"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+    }
+
+    @Test
+    public void testInvoiceSubtotalWithManySameProducts() {
+        Product onions = new TaxFreeProduct("Warzywa", new BigDecimal("10"));
+        invoice.addProduct(onions, 100);
+        Assert.assertThat(new BigDecimal("1000"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+    }
+
     @Test
     public void testInvoiceHasTheSameSubtotalAndTotalIfTaxIsZero() {
         Product taxFreeProduct = new TaxFreeProduct("Warzywa", new BigDecimal("199.99"));