diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..bc1eb9a
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,16 @@
+name: Test
+
+on:
+  push:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dart-lang/setup-dart@v1
+
+      - run: dart pub get
+      - run: dart analyze
+      - run: dart test
diff --git a/README.md b/README.md
index 5dcd175..e037528 100644
--- a/README.md
+++ b/README.md
@@ -3,28 +3,27 @@
 [creating packages](https://dart.dev/guides/libraries/create-library-packages)
 -->
 
-Library for sales calculations.
+# Salert
 
-## Features
-
-TODO: List what your package can do. Maybe include images, gifs, or videos.
+Library for sales data calculations.
 
-## Getting started
+## Features
 
-TODO: List prerequisites and provide or point to information on how to
-start using the package.
+- Sales items calculations (discount, subtotal, taxes, total).
+- Sales calculations (discount, subtotal, taxes, total).
 
 ## Usage
 
-TODO: Include short and useful examples for package users. Add longer examples
-to `/example` folder.
-
+Example for SRI invoice (Ecuador):
 ```dart
-const like = 'sample';
+// VAT tax with 13%.
+final vat = Tax(code: 'IVA13', unitValue: 13);
+// Invoice item (product or service).
+final item = Item(code: 'productX', quantity: 1, unitPrice: 10, taxes: [vat]);
+// The sale (aka Invoice)
+final sale = Sale(items: [item], tip: 1);
+// Calculate sale values.
+print('SUBTOTAL  ${sale.subtotal}');
+print('TAX  ${sale.tax}');
+print('TOTAL  ${sale.total}');
 ```
-
-## Additional information
-
-TODO: Tell users more about the package: where to find more information, how to
-contribute to the package, how to file issues, what response they can expect
-from the package authors, and more.
diff --git a/example/salert_example.dart b/example/salert_example.dart
index a4482e9..e2dab27 100644
--- a/example/salert_example.dart
+++ b/example/salert_example.dart
@@ -9,7 +9,7 @@ void ecuadorSriExample() {
   final ice = Tax(code: 'iceX', unitValue: 15, affectTax: true);
   // VAT tax with 13%.
   final vat = Tax(code: 'IVA13', unitValue: 13);
-  // Some item (product / service).
+  // Some item (product or service).
   final item = Item(
     code: 'productX',
     quantity: 2,
diff --git a/lib/src/discount.dart b/lib/src/discount.dart
index 96aef34..b030408 100644
--- a/lib/src/discount.dart
+++ b/lib/src/discount.dart
@@ -1,9 +1,14 @@
 import 'dart:math';
 
+/// Represents a discount.
 class Discount {
+  /// Amount for calculations.
   final double amount;
+  /// Unitary applies calculation for every item.
   final bool isUnitary;
+  /// If amount represents a percentage.
   final bool isPercentage;
+  /// True if applies before taxes.
   final bool affectTax;
 
   Discount({
diff --git a/lib/src/item.dart b/lib/src/item.dart
index a5177f9..3620fe1 100644
--- a/lib/src/item.dart
+++ b/lib/src/item.dart
@@ -66,6 +66,7 @@ class Item implements Sellable {
     return 0;
   }
 
+  /// Calculates tax amount.
   @override
   double get tax {
     return _taxAmountOf(subtotal);
@@ -94,6 +95,7 @@ class Item implements Sellable {
     return baseSubtotal - subtotal;
   }
 
+  /// Calculates total amount.
   @override
   double get total {
     return subtotal + tax;
diff --git a/lib/src/sale.dart b/lib/src/sale.dart
index 69c2e1f..5f6a159 100644
--- a/lib/src/sale.dart
+++ b/lib/src/sale.dart
@@ -29,7 +29,7 @@ class Sale implements Sellable {
         .reduce((s1, s2) => s1 + s2);
   }
 
-  /// Calculates tax amount including [discount].
+  /// Calculates tax amount.
   @override
   double get tax {
     return _items.map((item) => item.tax).reduce((s1, s2) => s1 + s2);
@@ -51,9 +51,10 @@ class Sale implements Sellable {
         .reduce((s1, s2) => s1 + s2);
   }
 
+  /// Calculates total amount.
   @override
   double get total {
-    return subtotal + tax;
+    return subtotal + tax + tip;
   }
 
   List<Item> get _items {
@@ -81,7 +82,7 @@ class Sale implements Sellable {
       final baseSubtotal =
           items.map((item) => item.subtotal).reduce((s1, s2) => s1 + s2);
       final baseTax = items.map((item) => item.tax).reduce((s1, s2) => s1 + s2);
-      final baseTotal = baseSubtotal + baseTax;
+      final baseTotal = baseSubtotal + baseTax + tip;
       var discountValue = discount!.discountOf(baseTotal);
       final discountedSubtotal = _inverseSubtotalOf(baseTotal - discountValue);
       discountValue = baseSubtotal - discountedSubtotal;
diff --git a/lib/src/sellable.dart b/lib/src/sellable.dart
index 5241daa..5221612 100644
--- a/lib/src/sellable.dart
+++ b/lib/src/sellable.dart
@@ -5,6 +5,7 @@ abstract class Sellable {
   /// Calculates subtotal amount including [discount] for given [taxCode] (before taxes).
   double subtotalOf(String taxCode);
 
+  /// Calculates tax amount.
   double get tax;
 
   /// Calculates tax amount including [discount] for given [taxCode].
@@ -13,5 +14,6 @@ abstract class Sellable {
   // Calculates discount amount before taxes.
   double get discountAmount;
 
+  /// Calculates total amount.
   double get total;
 }