From b9ffe96f553ee29f48d2cbb9f517d5685fa39b1e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Wojciech=20Fr=C4=85cz?= <fraczwojciech@gmail.com>
Date: Sat, 11 Feb 2017 23:58:33 +0100
Subject: [PATCH 1/9] Working all Invoice and Product tests

---
 .../java/pl/edu/agh/mwo/invoice/Invoice.java  | 35 +++++++++++++++----
 .../edu/agh/mwo/invoice/product/Product.java  | 16 ++++++---
 2 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
index 56fe02359..8599ebb76 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
@@ -1,30 +1,51 @@
 package pl.edu.agh.mwo.invoice;
 
 import java.math.BigDecimal;
-import java.util.Collection;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
 
 import pl.edu.agh.mwo.invoice.product.Product;
 
 public class Invoice {
-    private Collection<Product> products;
+    private Map<Product, Integer> products = new HashMap<Product, Integer>();
 
     public void addProduct(Product product) {
-        // TODO: implement
+        this.products.put(product, 1);
     }
 
     public void addProduct(Product product, Integer quantity) {
-        // TODO: implement
+        if (quantity <= 0) {
+            throw new IllegalArgumentException();
+        }
+        this.products.put(product, quantity);
     }
 
     public BigDecimal getSubtotal() {
-        return null;
+        return getTotal().subtract(getTax());
     }
 
     public BigDecimal getTax() {
-        return null;
+        BigDecimal totalTax = new BigDecimal(0);
+        Iterator<Map.Entry<Product, Integer>> it = products.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<Product, Integer> pair = it.next();
+            BigDecimal productTax = pair.getKey().getTaxOnly();
+            BigDecimal quantity = new BigDecimal(pair.getValue());
+            totalTax = totalTax.add(productTax.multiply(quantity));
+        }
+        return totalTax;
     }
 
     public BigDecimal getTotal() {
-        return null;
+        BigDecimal total = new BigDecimal(0);
+        Iterator<Map.Entry<Product, Integer>> it = products.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<Product, Integer> pair = it.next();
+            BigDecimal productPriceWithTax = pair.getKey().getPriceWithTax();
+            BigDecimal quantity = new BigDecimal(pair.getValue());
+            total = total.add(productPriceWithTax.multiply(quantity));
+        }
+        return total;
     }
 }
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java b/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
index 318de9ac9..b73269d75 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
@@ -10,24 +10,32 @@ public abstract class Product {
     private final BigDecimal taxPercent;
 
     protected Product(String name, BigDecimal price, BigDecimal tax) {
+        if (name == null || name.equals("") || price == null || tax == null || tax.compareTo(new BigDecimal(0)) < 0
+                || price.compareTo(new BigDecimal(0)) < 0) {
+            throw new IllegalArgumentException();
+        }
         this.name = name;
         this.price = price;
         this.taxPercent = tax;
     }
 
     public String getName() {
-        return null;
+        return name;
     }
 
     public BigDecimal getPrice() {
-        return null;
+        return price;
     }
 
     public BigDecimal getTaxPercent() {
-        return null;
+        return taxPercent;
     }
 
     public BigDecimal getPriceWithTax() {
-        return null;
+        return price.add(getTaxOnly());
+    }
+
+    public BigDecimal getTaxOnly() {
+        return price.multiply(taxPercent);
     }
 }

From fbb07dceb4407153fa266d69c832f48798da7a49 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Wojciech=20Fr=C4=85cz?= <fraczwojciech@gmail.com>
Date: Fri, 24 Feb 2017 23:32:19 +0100
Subject: [PATCH 2/9] Simplify invoice implementation

---
 .../java/pl/edu/agh/mwo/invoice/Invoice.java  | 43 ++++++++-----------
 .../edu/agh/mwo/invoice/product/Product.java  |  6 +--
 .../pl/edu/agh/mwo/invoice/InvoiceTest.java   | 22 +++++-----
 3 files changed, 30 insertions(+), 41 deletions(-)

diff --git a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
index 8599ebb76..72f4048d5 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
@@ -2,7 +2,6 @@
 
 import java.math.BigDecimal;
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.Map;
 
 import pl.edu.agh.mwo.invoice.product.Product;
@@ -11,41 +10,35 @@ public class Invoice {
     private Map<Product, Integer> products = new HashMap<Product, Integer>();
 
     public void addProduct(Product product) {
-        this.products.put(product, 1);
+        addProduct(product, 1);
     }
 
     public void addProduct(Product product, Integer quantity) {
-        if (quantity <= 0) {
+        if (product == null || quantity <= 0) {
             throw new IllegalArgumentException();
         }
-        this.products.put(product, quantity);
+        products.put(product, quantity);
     }
 
-    public BigDecimal getSubtotal() {
-        return getTotal().subtract(getTax());
+    public BigDecimal getNetTotal() {
+        BigDecimal totalNet = BigDecimal.ZERO;
+        for (Product product : products.keySet()) {
+            BigDecimal quantity = new BigDecimal(products.get(product));
+            totalNet = totalNet.add(product.getPrice().multiply(quantity));
+        }
+        return totalNet;
     }
 
-    public BigDecimal getTax() {
-        BigDecimal totalTax = new BigDecimal(0);
-        Iterator<Map.Entry<Product, Integer>> it = products.entrySet().iterator();
-        while (it.hasNext()) {
-            Map.Entry<Product, Integer> pair = it.next();
-            BigDecimal productTax = pair.getKey().getTaxOnly();
-            BigDecimal quantity = new BigDecimal(pair.getValue());
-            totalTax = totalTax.add(productTax.multiply(quantity));
-        }
-        return totalTax;
+    public BigDecimal getTaxTotal() {
+        return getGrossTotal().subtract(getNetTotal());
     }
 
-    public BigDecimal getTotal() {
-        BigDecimal total = new BigDecimal(0);
-        Iterator<Map.Entry<Product, Integer>> it = products.entrySet().iterator();
-        while (it.hasNext()) {
-            Map.Entry<Product, Integer> pair = it.next();
-            BigDecimal productPriceWithTax = pair.getKey().getPriceWithTax();
-            BigDecimal quantity = new BigDecimal(pair.getValue());
-            total = total.add(productPriceWithTax.multiply(quantity));
+    public BigDecimal getGrossTotal() {
+        BigDecimal totalGross = BigDecimal.ZERO;
+        for (Product product : products.keySet()) {
+            BigDecimal quantity = new BigDecimal(products.get(product));
+            totalGross = totalGross.add(product.getPriceWithTax().multiply(quantity));
         }
-        return total;
+        return totalGross;
     }
 }
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java b/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
index b73269d75..cd0f86a48 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
@@ -32,10 +32,6 @@ public BigDecimal getTaxPercent() {
     }
 
     public BigDecimal getPriceWithTax() {
-        return price.add(getTaxOnly());
-    }
-
-    public BigDecimal getTaxOnly() {
-        return price.multiply(taxPercent);
+        return price.multiply(taxPercent).add(price);
     }
 }
diff --git a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
index 7f4b6f795..50513171c 100644
--- a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
+++ b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
@@ -23,17 +23,17 @@ public void createEmptyInvoiceForTheTest() {
 
     @Test
     public void testEmptyInvoiceHasEmptySubtotal() {
-        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getNetTotal()));
     }
 
     @Test
     public void testEmptyInvoiceHasEmptyTaxAmount() {
-        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getTax()));
+        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getTaxTotal()));
     }
 
     @Test
     public void testEmptyInvoiceHasEmptyTotal() {
-        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getTotal()));
+        Assert.assertThat(BigDecimal.ZERO, Matchers.comparesEqualTo(invoice.getGrossTotal()));
     }
 
     @Test
@@ -42,21 +42,21 @@ public void testInvoiceSubtotalWithTwoDifferentProducts() {
         Product apples = new TaxFreeProduct("Owoce", new BigDecimal("10"));
         invoice.addProduct(onions);
         invoice.addProduct(apples);
-        Assert.assertThat(new BigDecimal("20"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(new BigDecimal("20"), Matchers.comparesEqualTo(invoice.getNetTotal()));
     }
 
     @Test
     public void testInvoiceSubtotalWithManySameProducts() {
         Product onions = new TaxFreeProduct("Warzywa", BigDecimal.valueOf(10));
         invoice.addProduct(onions, 100);
-        Assert.assertThat(new BigDecimal("1000"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(new BigDecimal("1000"), Matchers.comparesEqualTo(invoice.getNetTotal()));
     }
 
     @Test
     public void testInvoiceHasTheSameSubtotalAndTotalIfTaxIsZero() {
         Product taxFreeProduct = new TaxFreeProduct("Warzywa", new BigDecimal("199.99"));
         invoice.addProduct(taxFreeProduct);
-        Assert.assertThat(invoice.getTotal(), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(invoice.getNetTotal(), Matchers.comparesEqualTo(invoice.getGrossTotal()));
     }
 
     @Test
@@ -64,7 +64,7 @@ public void testInvoiceHasProperSubtotalForManyProducts() {
         invoice.addProduct(new TaxFreeProduct("Owoce", new BigDecimal("200")));
         invoice.addProduct(new DairyProduct("Maslanka", new BigDecimal("100")));
         invoice.addProduct(new OtherProduct("Wino", new BigDecimal("10")));
-        Assert.assertThat(new BigDecimal("310"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(new BigDecimal("310"), Matchers.comparesEqualTo(invoice.getNetTotal()));
     }
 
     @Test
@@ -75,7 +75,7 @@ public void testInvoiceHasProperTaxValueForManyProduct() {
         invoice.addProduct(new DairyProduct("Kefir", new BigDecimal("100")));
         // tax: 2.30
         invoice.addProduct(new OtherProduct("Piwko", new BigDecimal("10")));
-        Assert.assertThat(new BigDecimal("10.30"), Matchers.comparesEqualTo(invoice.getTax()));
+        Assert.assertThat(new BigDecimal("10.30"), Matchers.comparesEqualTo(invoice.getTaxTotal()));
     }
 
     @Test
@@ -86,7 +86,7 @@ public void testInvoiceHasProperTotalValueForManyProduct() {
         invoice.addProduct(new DairyProduct("Maslo", new BigDecimal("100")));
         // price with tax: 12.30
         invoice.addProduct(new OtherProduct("Chipsy", new BigDecimal("10")));
-        Assert.assertThat(new BigDecimal("320.30"), Matchers.comparesEqualTo(invoice.getTotal()));
+        Assert.assertThat(new BigDecimal("320.30"), Matchers.comparesEqualTo(invoice.getGrossTotal()));
     }
 
     @Test
@@ -97,7 +97,7 @@ public void testInvoiceHasPropoerSubtotalWithQuantityMoreThanOne() {
         invoice.addProduct(new DairyProduct("Kozi Serek", new BigDecimal("10")), 3);
         // 1000x pinezka - price: 10
         invoice.addProduct(new OtherProduct("Pinezka", new BigDecimal("0.01")), 1000);
-        Assert.assertThat(new BigDecimal("50"), Matchers.comparesEqualTo(invoice.getSubtotal()));
+        Assert.assertThat(new BigDecimal("50"), Matchers.comparesEqualTo(invoice.getNetTotal()));
     }
 
     @Test
@@ -108,7 +108,7 @@ public void testInvoiceHasPropoerTotalWithQuantityMoreThanOne() {
         invoice.addProduct(new DairyProduct("Chedar", new BigDecimal("10")), 3);
         // 1000x pinezka - price with tax: 12.30
         invoice.addProduct(new OtherProduct("Pinezka", new BigDecimal("0.01")), 1000);
-        Assert.assertThat(new BigDecimal("54.70"), Matchers.comparesEqualTo(invoice.getTotal()));
+        Assert.assertThat(new BigDecimal("54.70"), Matchers.comparesEqualTo(invoice.getGrossTotal()));
     }
 
     @Test(expected = IllegalArgumentException.class)

From bb14e3621b1308a923c4c96738aad81e67082cc3 Mon Sep 17 00:00:00 2001
From: Aleksandra <aleksandra.paperz@email.com>
Date: Sun, 14 Jun 2026 20:16:45 +0200
Subject: [PATCH 3/9] 1

---
 .github/workflows/github-actions.yml      | 15 +++++++
 .github/workflows/qodana_code_quality.yml | 40 ++++++++++++++++++
 qodana.yaml                               | 49 +++++++++++++++++++++++
 3 files changed, 104 insertions(+)
 create mode 100644 .github/workflows/github-actions.yml
 create mode 100644 .github/workflows/qodana_code_quality.yml
 create mode 100644 qodana.yaml

diff --git a/.github/workflows/github-actions.yml b/.github/workflows/github-actions.yml
new file mode 100644
index 000000000..8fb587348
--- /dev/null
+++ b/.github/workflows/github-actions.yml
@@ -0,0 +1,15 @@
+name: CI for Java Invoice
+on: [push]
+jobs:
+  test:
+    name: Unit tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK
+        uses: actions/setup-java@v2
+        with:
+          java-version: '17'
+          distribution: 'adopt'
+      - name: Test
+        run: mvn test
\ No newline at end of file
diff --git a/.github/workflows/qodana_code_quality.yml b/.github/workflows/qodana_code_quality.yml
new file mode 100644
index 000000000..d1f49a71a
--- /dev/null
+++ b/.github/workflows/qodana_code_quality.yml
@@ -0,0 +1,40 @@
+#-------------------------------------------------------------------------------#
+#            Discover all capabilities of Qodana in our documentation           #
+#             https://www.jetbrains.com/help/qodana/about-qodana.html           #
+#-------------------------------------------------------------------------------#
+
+name: Qodana
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+      - master
+      - tdd
+
+jobs:
+  qodana:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+      checks: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+      - name: 'Qodana Scan'
+        uses: JetBrains/qodana-action@v2026.1
+        env:
+          QODANA_TOKEN: ${{ secrets.QODANA_TOKEN }}
+        with:
+          # When pr-mode is set to true, Qodana analyzes only the files that have been changed
+          pr-mode: false
+          use-caches: true
+          post-pr-comment: true
+          use-annotations: true
+          # Upload Qodana results (SARIF, other artifacts, logs) as an artifact to the job
+          upload-result: false
+          # quick-fixes available in Ultimate and Ultimate Plus plans
+          push-fixes: 'none'
\ No newline at end of file
diff --git a/qodana.yaml b/qodana.yaml
new file mode 100644
index 000000000..fcaa9673e
--- /dev/null
+++ b/qodana.yaml
@@ -0,0 +1,49 @@
+#-------------------------------------------------------------------------------#
+#               Qodana analysis is configured by qodana.yaml file               #
+#             https://www.jetbrains.com/help/qodana/qodana-yaml.html            #
+#-------------------------------------------------------------------------------#
+
+#################################################################################
+#              WARNING: Do not store sensitive information in this file,        #
+#               as its contents will be included in the Qodana report.          #
+#################################################################################
+version: "1.0"
+
+#Specify inspection profile for code analysis
+profile:
+  name: qodana.starter
+
+#Enable inspections
+#include:
+#  - name: <SomeEnabledInspectionId>
+
+#Disable inspections
+#exclude:
+#  - name: <SomeDisabledInspectionId>
+#    paths:
+#      - <path/where/not/run/inspection>
+
+projectJDK: "26" #(Applied in CI/CD pipeline)
+
+#Execute shell command before Qodana execution (Applied in CI/CD pipeline)
+#bootstrap: sh ./prepare-qodana.sh
+
+#Install IDE plugins before Qodana execution (Applied in CI/CD pipeline)
+#plugins:
+#  - id: <plugin.id> #(plugin id can be found at https://plugins.jetbrains.com)
+
+# Quality gate. Will fail the CI/CD pipeline if any condition is not met
+# severityThresholds - configures maximum thresholds for different problem severities
+# testCoverageThresholds - configures minimum code coverage on a whole project and newly added code
+# Code Coverage is available in Ultimate and Ultimate Plus plans
+#failureConditions:
+#  severityThresholds:
+#    any: 15
+#    critical: 5
+#  testCoverageThresholds:
+#    fresh: 70
+#    total: 50
+  
+#Qodana supports other languages, for example, Python, JavaScript, TypeScript, Go, C#, PHP
+#For all supported languages see https://www.jetbrains.com/help/qodana/linters.html
+linter: jetbrains/qodana-jvm-community:2026.1

From 51a62b4b19b52d6cc226c63d2ec0e04b66cc4a25 Mon Sep 17 00:00:00 2001
From: Aleksandra <aleksandra.paperz@email.com>
Date: Wed, 17 Jun 2026 14:46:21 +0200
Subject: [PATCH 4/9] 2

---
 config/checkstyle.xml                         | 295 ++++++++++++++++++
 pom.xml                                       |  28 +-
 .../pl/edu/agh/mwo/invoice/package-info.java  |   4 +
 .../agh/mwo/invoice/product/package-info.java |   4 +
 4 files changed, 330 insertions(+), 1 deletion(-)
 create mode 100644 config/checkstyle.xml
 create mode 100644 src/main/java/pl/edu/agh/mwo/invoice/package-info.java
 create mode 100644 src/main/java/pl/edu/agh/mwo/invoice/product/package-info.java

diff --git a/config/checkstyle.xml b/config/checkstyle.xml
new file mode 100644
index 000000000..24335bb6c
--- /dev/null
+++ b/config/checkstyle.xml
@@ -0,0 +1,295 @@
+<?xml version="1.0"?>
+<!--
+These rules are based on the
+https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
+but without javadoc requirements and with severity set to error.
+-->
+<!DOCTYPE module PUBLIC
+        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+        "https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="Checker">
+    <property name="charset" value="UTF-8"/>
+
+    <property name="severity" value="error"/>
+
+    <property name="fileExtensions" value="java, properties, xml"/>
+
+    <module name="FileTabCharacter">
+        <property name="eachLine" value="true"/>
+    </module>
+
+    <module name="LineLength">
+        <property name="fileExtensions" value="java"/>
+        <property name="max" value="120"/>
+    </module>
+
+    <module name="TreeWalker">
+        <module name="MagicNumber"/>
+        <module name="OuterTypeFilename"/>
+        <module name="IllegalTokenText">
+            <property name="tokens" value="STRING_LITERAL, CHAR_LITERAL"/>
+            <property name="format"
+                      value="\\u00(09|0(a|A)|0(c|C)|0(d|D)|22|27|5(C|c))|\\(0(10|11|12|14|15|42|47)|134)"/>
+            <property name="message"
+                      value="Consider using special escape sequence instead of octal value or Unicode escaped value."/>
+        </module>
+        <module name="AvoidEscapedUnicodeCharacters">
+            <property name="allowEscapesForControlCharacters" value="true"/>
+            <property name="allowByTailComment" value="true"/>
+            <property name="allowNonPrintableEscapes" value="true"/>
+        </module>
+        <module name="AvoidStarImport"/>
+        <module name="OneTopLevelClass"/>
+        <module name="NoLineWrap">
+            <property name="tokens" value="PACKAGE_DEF, IMPORT, STATIC_IMPORT"/>
+        </module>
+        <module name="EmptyBlock">
+            <property name="option" value="TEXT"/>
+            <property name="tokens"
+                      value="LITERAL_TRY, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE, LITERAL_SWITCH"/>
+        </module>
+        <module name="NeedBraces">
+            <property name="tokens"
+                      value="LITERAL_DO, LITERAL_ELSE, LITERAL_FOR, LITERAL_IF, LITERAL_WHILE"/>
+        </module>
+        <module name="LeftCurly">
+            <property name="tokens"
+                      value="ANNOTATION_DEF, CLASS_DEF, CTOR_DEF, ENUM_CONSTANT_DEF, ENUM_DEF,
+                    INTERFACE_DEF, LAMBDA, LITERAL_CASE, LITERAL_CATCH, LITERAL_DEFAULT,
+                    LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF,
+                    LITERAL_SWITCH, LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, METHOD_DEF,
+                    OBJBLOCK, STATIC_INIT"/>
+        </module>
+        <module name="RightCurly">
+            <property name="id" value="RightCurlySame"/>
+            <property name="tokens"
+                      value="LITERAL_TRY, LITERAL_CATCH, LITERAL_FINALLY, LITERAL_IF, LITERAL_ELSE,
+                    LITERAL_DO"/>
+        </module>
+        <module name="RightCurly">
+            <property name="id" value="RightCurlyAlone"/>
+            <property name="option" value="alone"/>
+            <property name="tokens"
+                      value="CLASS_DEF, METHOD_DEF, CTOR_DEF, LITERAL_FOR, LITERAL_WHILE, STATIC_INIT,
+                    INSTANCE_INIT, ANNOTATION_DEF, ENUM_DEF"/>
+        </module>
+        <module name="SuppressionXpathSingleFilter">
+            <!-- suppresion is required till https://github.com/checkstyle/checkstyle/issues/7541 -->
+            <property name="id" value="RightCurlyAlone"/>
+            <property name="query" value="//RCURLY[parent::SLIST[count(./*)=1]
+                                                 or preceding-sibling::*[last()][self::LCURLY]]"/>
+        </module>
+        <module name="WhitespaceAfter">
+            <property name="tokens"
+                      value="COMMA, SEMI, TYPECAST, LITERAL_IF, LITERAL_ELSE,
+                    LITERAL_WHILE, LITERAL_DO, LITERAL_FOR, DO_WHILE"/>
+        </module>
+        <module name="WhitespaceAround">
+            <property name="allowEmptyConstructors" value="true"/>
+            <property name="allowEmptyLambdas" value="true"/>
+            <property name="allowEmptyMethods" value="true"/>
+            <property name="allowEmptyTypes" value="true"/>
+            <property name="allowEmptyLoops" value="true"/>
+            <property name="tokens"
+                      value="ASSIGN, BAND, BAND_ASSIGN, BOR, BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR,
+                    BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN, DO_WHILE, EQUAL, GE, GT, LAMBDA, LAND,
+                    LCURLY, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE, LITERAL_FINALLY,
+                    LITERAL_FOR, LITERAL_IF, LITERAL_RETURN, LITERAL_SWITCH, LITERAL_SYNCHRONIZED,
+                     LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS, MINUS_ASSIGN, MOD, MOD_ASSIGN,
+                     NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION, RCURLY, SL, SLIST, SL_ASSIGN, SR,
+                     SR_ASSIGN, STAR, STAR_ASSIGN, LITERAL_ASSERT, TYPE_EXTENSION_AND"/>
+            <message key="ws.notFollowed"
+                     value="WhitespaceAround: ''{0}'' is not followed by whitespace. Empty blocks may only be represented as '{}' when not part of a multi-block statement (4.1.3)"/>
+            <message key="ws.notPreceded"
+                     value="WhitespaceAround: ''{0}'' is not preceded with whitespace."/>
+        </module>
+        <module name="OneStatementPerLine"/>
+        <module name="MultipleVariableDeclarations"/>
+        <module name="ArrayTypeStyle"/>
+        <module name="MissingSwitchDefault"/>
+        <module name="FallThrough"/>
+        <module name="UpperEll"/>
+        <module name="ModifierOrder"/>
+        <module name="EmptyLineSeparator">
+            <property name="tokens"
+                      value="PACKAGE_DEF, IMPORT, STATIC_IMPORT, CLASS_DEF, INTERFACE_DEF, ENUM_DEF,
+                    STATIC_INIT, INSTANCE_INIT, METHOD_DEF, CTOR_DEF, VARIABLE_DEF"/>
+            <property name="allowNoEmptyLineBetweenFields" value="true"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapDot"/>
+            <property name="tokens" value="DOT"/>
+            <property name="option" value="nl"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapComma"/>
+            <property name="tokens" value="COMMA"/>
+            <property name="option" value="EOL"/>
+        </module>
+        <module name="SeparatorWrap">
+            <!-- ELLIPSIS is EOL until https://github.com/google/styleguide/issues/258 -->
+            <property name="id" value="SeparatorWrapEllipsis"/>
+            <property name="tokens" value="ELLIPSIS"/>
+            <property name="option" value="EOL"/>
+        </module>
+        <module name="SeparatorWrap">
+            <!-- ARRAY_DECLARATOR is EOL until https://github.com/google/styleguide/issues/259 -->
+            <property name="id" value="SeparatorWrapArrayDeclarator"/>
+            <property name="tokens" value="ARRAY_DECLARATOR"/>
+            <property name="option" value="EOL"/>
+        </module>
+        <module name="SeparatorWrap">
+            <property name="id" value="SeparatorWrapMethodRef"/>
+            <property name="tokens" value="METHOD_REF"/>
+            <property name="option" value="nl"/>
+        </module>
+        <module name="PackageName">
+            <property name="format" value="^[a-z]+(\.[a-z][a-z0-9]*)*$"/>
+            <message key="name.invalidPattern"
+                     value="Package name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="TypeName">
+            <property name="tokens" value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, ANNOTATION_DEF"/>
+            <message key="name.invalidPattern"
+                     value="Type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="MemberName">
+            <property name="format" value="^[a-z][a-z0-9][a-zA-Z0-9]*$"/>
+            <message key="name.invalidPattern"
+                     value="Member name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="ParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Parameter name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="LambdaParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Lambda parameter name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="CatchParameterName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Catch parameter name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="LocalVariableName">
+            <property name="format" value="^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"/>
+            <message key="name.invalidPattern"
+                     value="Local variable name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="ClassTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+                     value="Class type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="MethodTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+                     value="Method type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="InterfaceTypeParameterName">
+            <property name="format" value="(^[A-Z][0-9]?)$|([A-Z][a-zA-Z0-9]*[T]$)"/>
+            <message key="name.invalidPattern"
+                     value="Interface type name ''{0}'' must match pattern ''{1}''."/>
+        </module>
+        <module name="NoFinalizer"/>
+        <module name="GenericWhitespace">
+            <message key="ws.followed"
+                     value="GenericWhitespace ''{0}'' is followed by whitespace."/>
+            <message key="ws.preceded"
+                     value="GenericWhitespace ''{0}'' is preceded with whitespace."/>
+            <message key="ws.illegalFollow"
+                     value="GenericWhitespace ''{0}'' should followed by whitespace."/>
+            <message key="ws.notPreceded"
+                     value="GenericWhitespace ''{0}'' is not preceded with whitespace."/>
+        </module>
+        <module name="Indentation">
+            <property name="basicOffset" value="4"/>
+            <property name="braceAdjustment" value="0"/>
+            <property name="caseIndent" value="4"/>
+            <property name="throwsIndent" value="4"/>
+            <property name="lineWrappingIndentation" value="4"/>
+            <property name="arrayInitIndent" value="4"/>
+        </module>
+        <module name="AbbreviationAsWordInName">
+            <property name="ignoreFinal" value="false"/>
+            <property name="allowedAbbreviationLength" value="1"/>
+            <property name="tokens"
+                      value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, ANNOTATION_DEF, ANNOTATION_FIELD_DEF,
+                    PARAMETER_DEF, VARIABLE_DEF, METHOD_DEF"/>
+        </module>
+        <module name="OverloadMethodsDeclarationOrder"/>
+        <module name="VariableDeclarationUsageDistance"/>
+        <module name="MethodParamPad">
+            <property name="tokens"
+                      value="CTOR_DEF, LITERAL_NEW, METHOD_CALL, METHOD_DEF,
+                    SUPER_CTOR_CALL, ENUM_CONSTANT_DEF"/>
+        </module>
+        <module name="NoWhitespaceBefore">
+            <property name="tokens"
+                      value="COMMA, SEMI, POST_INC, POST_DEC, DOT, ELLIPSIS, METHOD_REF"/>
+            <property name="allowLineBreaks" value="true"/>
+        </module>
+        <module name="ParenPad">
+            <property name="tokens"
+                      value="ANNOTATION, ANNOTATION_FIELD_DEF, CTOR_CALL, CTOR_DEF, DOT, ENUM_CONSTANT_DEF,
+                    EXPR, LITERAL_CATCH, LITERAL_DO, LITERAL_FOR, LITERAL_IF, LITERAL_NEW,
+                    LITERAL_SWITCH, LITERAL_SYNCHRONIZED, LITERAL_WHILE, METHOD_CALL,
+                    METHOD_DEF, QUESTION, RESOURCE_SPECIFICATION, SUPER_CTOR_CALL, LAMBDA"/>
+        </module>
+        <module name="OperatorWrap">
+            <property name="option" value="NL"/>
+            <property name="tokens"
+                      value="BAND, BOR, BSR, BXOR, DIV, EQUAL, GE, GT, LAND, LE, LITERAL_INSTANCEOF, LOR,
+                    LT, MINUS, MOD, NOT_EQUAL, PLUS, QUESTION, SL, SR, STAR, METHOD_REF "/>
+        </module>
+        <module name="AnnotationLocation">
+            <property name="id" value="AnnotationLocationMostCases"/>
+            <property name="tokens"
+                      value="CLASS_DEF, INTERFACE_DEF, ENUM_DEF, METHOD_DEF, CTOR_DEF"/>
+        </module>
+        <module name="AnnotationLocation">
+            <property name="id" value="AnnotationLocationVariables"/>
+            <property name="tokens" value="VARIABLE_DEF"/>
+            <property name="allowSamelineMultipleAnnotations" value="true"/>
+        </module>
+        <module name="NonEmptyAtclauseDescription">
+            <property name="severity" value="ignore"/>
+        </module>
+        <module name="InvalidJavadocPosition">
+            <property name="severity" value="ignore"/>
+        </module>
+        <module name="JavadocTagContinuationIndentation">
+            <property name="severity" value="ignore"/>
+        </module>
+        <module name="SummaryJavadoc">
+            <property name="severity" value="ignore"/>
+        </module>
+        <module name="JavadocParagraph">
+            <property name="severity" value="ignore"/>
+        </module>
+        <module name="AtclauseOrder">
+            <property name="severity" value="ignore"/>
+        </module>
+        <module name="JavadocMethod">
+            <property name="severity" value="ignore"/>
+        </module>
+        <module name="SingleLineJavadoc">
+            <property name="severity" value="ignore"/>
+        </module>
+
+        <module name="EmptyCatchBlock">
+            <property name="exceptionVariableName" value="expected"/>
+        </module>
+        <module name="CommentsIndentation">
+            <property name="tokens" value="SINGLE_LINE_COMMENT, BLOCK_COMMENT_BEGIN"/>
+        </module>
+        <!-- https://checkstyle.org/config_filters.html#SuppressionXpathFilter -->
+        <module name="SuppressionXpathFilter">
+            <property name="file" value="${org.checkstyle.google.suppressionxpathfilter.config}"
+                      default="checkstyle-xpath-suppressions.xml"/>
+            <property name="optional" value="true"/>
+        </module>
+    </module>
+</module>
\ No newline at end of file
diff --git a/pom.xml b/pom.xml
index 2d40c3e8a..17a596e95 100644
--- a/pom.xml
+++ b/pom.xml
@@ -17,6 +17,26 @@
     <build>
         <sourceDirectory>src/main/java</sourceDirectory>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-checkstyle-plugin</artifactId>
+                <version>3.2.1</version>
+                <configuration>
+                    <configLocation>config/checkstyle.xml</configLocation>
+                    <consoleOutput>true</consoleOutput>
+                    <failsOnError>true</failsOnError>
+                    <linkXRef>false</linkXRef>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>validate</id>
+                        <phase>validate</phase>
+                        <goals>
+                            <goal>check</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
@@ -40,5 +60,11 @@
             <artifactId>hamcrest-all</artifactId>
             <version>1.3</version>
         </dependency>
+        <dependency>
+            <groupId>org.hamcrest</groupId>
+            <artifactId>hamcrest</artifactId>
+            <version>2.2</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
-</project>
+</project>
\ No newline at end of file
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/package-info.java b/src/main/java/pl/edu/agh/mwo/invoice/package-info.java
new file mode 100644
index 000000000..05fbd5def
--- /dev/null
+++ b/src/main/java/pl/edu/agh/mwo/invoice/package-info.java
@@ -0,0 +1,4 @@
+/**
+ * Provides classes for creating and managing invoices.
+ */
+package pl.edu.agh.mwo.invoice;
\ No newline at end of file
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/product/package-info.java b/src/main/java/pl/edu/agh/mwo/invoice/product/package-info.java
new file mode 100644
index 000000000..b08eb4784
--- /dev/null
+++ b/src/main/java/pl/edu/agh/mwo/invoice/product/package-info.java
@@ -0,0 +1,4 @@
+/**
+ * Provides classes representing different types of products.
+ */
+package pl.edu.agh.mwo.invoice.product;
\ No newline at end of file

From 378ea5ad89325700837447fb750b3f508237a9cd Mon Sep 17 00:00:00 2001
From: Aleksandra <aleksandra.paperz@email.com>
Date: Wed, 17 Jun 2026 14:49:49 +0200
Subject: [PATCH 5/9] 2

---
 pom.xml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pom.xml b/pom.xml
index 17a596e95..2027618f0 100644
--- a/pom.xml
+++ b/pom.xml
@@ -52,7 +52,7 @@
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
-            <version>4.12</version>
+            <version>4.13.2</version>
             <scope>test</scope>
         </dependency>
         <dependency>

From b3eab2ff2c35c8a88ead48d1cf9f3cf010953e75 Mon Sep 17 00:00:00 2001
From: Aleksandra <aleksandra.paperz@email.com>
Date: Wed, 17 Jun 2026 18:56:54 +0200
Subject: [PATCH 6/9] Numerowanie faktur

---
 effective-pom.xml                             | 273 ++++++++++++++++++
 pom.xml                                       |  20 +-
 .../java/pl/edu/agh/mwo/invoice/Invoice.java  |  12 +-
 .../pl/edu/agh/mwo/invoice/InvoiceTest.java   |  12 +
 4 files changed, 307 insertions(+), 10 deletions(-)
 create mode 100644 effective-pom.xml

diff --git a/effective-pom.xml b/effective-pom.xml
new file mode 100644
index 000000000..21a89f947
--- /dev/null
+++ b/effective-pom.xml
@@ -0,0 +1,273 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- ====================================================================== -->
+<!--                                                                        -->
+<!-- Generated by Maven Help Plugin                                         -->
+<!-- See: https://maven.apache.org/plugins/maven-help-plugin/               -->
+<!--                                                                        -->
+<!-- ====================================================================== -->
+<!-- ====================================================================== -->
+<!--                                                                        -->
+<!-- Effective POM for project                                              -->
+<!-- 'pl.edu.agh.mwo.hellomaven:hello-maven:jar:1.0.0-SNAPSHOT'             -->
+<!--                                                                        -->
+<!-- ====================================================================== -->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>pl.edu.agh.mwo.hellomaven</groupId>
+  <artifactId>hello-maven</artifactId>
+  <version>1.0.0-SNAPSHOT</version>
+  <properties>
+    <maven.compiler.source>17</maven.compiler.source>
+    <maven.compiler.target>17</maven.compiler.target>
+    <maven.jar.plugin.version>3.2.0</maven.jar.plugin.version>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+  </properties>
+  <dependencies>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-api</artifactId>
+      <version>6.0.3</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+  <repositories>
+    <repository>
+      <snapshots>
+        <enabled>false</enabled>
+      </snapshots>
+      <id>central</id>
+      <name>Central Repository</name>
+      <url>https://repo.maven.apache.org/maven2</url>
+    </repository>
+  </repositories>
+  <pluginRepositories>
+    <pluginRepository>
+      <snapshots>
+        <enabled>false</enabled>
+      </snapshots>
+      <id>central</id>
+      <name>Central Repository</name>
+      <url>https://repo.maven.apache.org/maven2</url>
+    </pluginRepository>
+  </pluginRepositories>
+  <build>
+    <sourceDirectory>/Users/olenka/Desktop/java-invoice-tdd/src/main/java</sourceDirectory>
+    <scriptSourceDirectory>/Users/olenka/Desktop/java-invoice-tdd/src/main/scripts</scriptSourceDirectory>
+    <testSourceDirectory>/Users/olenka/Desktop/java-invoice-tdd/src/test/java</testSourceDirectory>
+    <outputDirectory>/Users/olenka/Desktop/java-invoice-tdd/target/classes</outputDirectory>
+    <testOutputDirectory>/Users/olenka/Desktop/java-invoice-tdd/target/test-classes</testOutputDirectory>
+    <resources>
+      <resource>
+        <directory>/Users/olenka/Desktop/java-invoice-tdd/src/main/resources</directory>
+      </resource>
+    </resources>
+    <testResources>
+      <testResource>
+        <directory>/Users/olenka/Desktop/java-invoice-tdd/src/test/resources</directory>
+      </testResource>
+    </testResources>
+    <directory>/Users/olenka/Desktop/java-invoice-tdd/target</directory>
+    <finalName>hello-maven-1.0.0-SNAPSHOT</finalName>
+    <pluginManagement>
+      <plugins>
+        <plugin>
+          <artifactId>maven-antrun-plugin</artifactId>
+          <version>3.1.0</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-assembly-plugin</artifactId>
+          <version>3.7.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-dependency-plugin</artifactId>
+          <version>3.7.0</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-release-plugin</artifactId>
+          <version>3.0.1</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+    <plugins>
+      <plugin>
+        <artifactId>maven-jar-plugin</artifactId>
+        <version>3.2.0</version>
+        <executions>
+          <execution>
+            <id>default-jar</id>
+            <phase>package</phase>
+            <goals>
+              <goal>jar</goal>
+            </goals>
+            <configuration>
+              <archive>
+                <manifest>
+                  <addClasspath>true</addClasspath>
+                  <mainClass>pl.edu.agh.mwo.hellomaven.App</mainClass>
+                </manifest>
+              </archive>
+            </configuration>
+          </execution>
+        </executions>
+        <configuration>
+          <archive>
+            <manifest>
+              <addClasspath>true</addClasspath>
+              <mainClass>pl.edu.agh.mwo.hellomaven.App</mainClass>
+            </manifest>
+          </archive>
+        </configuration>
+      </plugin>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>exec-maven-plugin</artifactId>
+        <version>1.2.1</version>
+        <configuration>
+          <mainClass>pl.edu.agh.mwo.hellomaven.App</mainClass>
+        </configuration>
+      </plugin>
+      <plugin>
+        <artifactId>maven-clean-plugin</artifactId>
+        <version>3.2.0</version>
+        <executions>
+          <execution>
+            <id>default-clean</id>
+            <phase>clean</phase>
+            <goals>
+              <goal>clean</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <artifactId>maven-resources-plugin</artifactId>
+        <version>3.4.0</version>
+        <executions>
+          <execution>
+            <id>default-testResources</id>
+            <phase>process-test-resources</phase>
+            <goals>
+              <goal>testResources</goal>
+            </goals>
+          </execution>
+          <execution>
+            <id>default-resources</id>
+            <phase>process-resources</phase>
+            <goals>
+              <goal>resources</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.15.0</version>
+        <executions>
+          <execution>
+            <id>default-compile</id>
+            <phase>compile</phase>
+            <goals>
+              <goal>compile</goal>
+            </goals>
+          </execution>
+          <execution>
+            <id>default-testCompile</id>
+            <phase>test-compile</phase>
+            <goals>
+              <goal>testCompile</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <version>3.5.4</version>
+        <executions>
+          <execution>
+            <id>default-test</id>
+            <phase>test</phase>
+            <goals>
+              <goal>test</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <artifactId>maven-install-plugin</artifactId>
+        <version>3.1.4</version>
+        <executions>
+          <execution>
+            <id>default-install</id>
+            <phase>install</phase>
+            <goals>
+              <goal>install</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <artifactId>maven-deploy-plugin</artifactId>
+        <version>3.1.4</version>
+        <executions>
+          <execution>
+            <id>default-deploy</id>
+            <phase>deploy</phase>
+            <goals>
+              <goal>deploy</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <artifactId>maven-site-plugin</artifactId>
+        <version>3.12.1</version>
+        <executions>
+          <execution>
+            <id>default-site</id>
+            <phase>site</phase>
+            <goals>
+              <goal>site</goal>
+            </goals>
+            <configuration>
+              <outputDirectory>/Users/olenka/Desktop/java-invoice-tdd/target/site</outputDirectory>
+              <reportPlugins>
+                <reportPlugin>
+                  <groupId>org.apache.maven.plugins</groupId>
+                  <artifactId>maven-project-info-reports-plugin</artifactId>
+                </reportPlugin>
+              </reportPlugins>
+            </configuration>
+          </execution>
+          <execution>
+            <id>default-deploy</id>
+            <phase>site-deploy</phase>
+            <goals>
+              <goal>deploy</goal>
+            </goals>
+            <configuration>
+              <outputDirectory>/Users/olenka/Desktop/java-invoice-tdd/target/site</outputDirectory>
+              <reportPlugins>
+                <reportPlugin>
+                  <groupId>org.apache.maven.plugins</groupId>
+                  <artifactId>maven-project-info-reports-plugin</artifactId>
+                </reportPlugin>
+              </reportPlugins>
+            </configuration>
+          </execution>
+        </executions>
+        <configuration>
+          <outputDirectory>/Users/olenka/Desktop/java-invoice-tdd/target/site</outputDirectory>
+          <reportPlugins>
+            <reportPlugin>
+              <groupId>org.apache.maven.plugins</groupId>
+              <artifactId>maven-project-info-reports-plugin</artifactId>
+            </reportPlugin>
+          </reportPlugins>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+  <reporting>
+    <outputDirectory>/Users/olenka/Desktop/java-invoice-tdd/target/site</outputDirectory>
+  </reporting>
+</project>
diff --git a/pom.xml b/pom.xml
index 2027618f0..411c4d9c9 100644
--- a/pom.xml
+++ b/pom.xml
@@ -20,13 +20,15 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-checkstyle-plugin</artifactId>
-                <version>3.2.1</version>
+                <version>3.3.1</version>
                 <configuration>
-                    <configLocation>config/checkstyle.xml</configLocation>
+                    <configLocation>
+                        ${project.basedir}/config/checkstyle.xml
+                    </configLocation>
                     <consoleOutput>true</consoleOutput>
-                    <failsOnError>true</failsOnError>
-                    <linkXRef>false</linkXRef>
-                </configuration>
+                <failsOnError>true</failsOnError>
+                <linkXRef>false</linkXRef>
+            </configuration>
                 <executions>
                     <execution>
                         <id>validate</id>
@@ -40,10 +42,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <configuration>
-                    <source>17</source>
-                    <target>17</target>
-                </configuration>
+                <version>3.13.0</version> <configuration>
+                <source>17</source>
+                <target>17</target>
+            </configuration>
             </plugin>
         </plugins>
     </build>
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
index 72f4048d5..c756ee549 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
@@ -7,7 +7,17 @@
 import pl.edu.agh.mwo.invoice.product.Product;
 
 public class Invoice {
-    private Map<Product, Integer> products = new HashMap<Product, Integer>();
+    private static int nextNumber = 1;
+    private final int number;
+    private final Map<Product, Integer> products = new HashMap<Product, Integer>();
+
+    public Invoice() {
+        number = nextNumber++;
+    }
+
+    public int getNumber() {
+        return number;
+    }
 
     public void addProduct(Product product) {
         addProduct(product, 1);
diff --git a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
index 50513171c..13ac02a96 100644
--- a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
+++ b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
@@ -16,6 +16,7 @@
 public class InvoiceTest {
     private Invoice invoice;
 
+
     @Before
     public void createEmptyInvoiceForTheTest() {
         invoice = new Invoice();
@@ -125,4 +126,15 @@ public void testInvoiceWithNegativeQuantity() {
     public void testAddingNullProduct() {
         invoice.addProduct(null);
     }
+
+    @Test
+    public void testInvoiceNumbersAreAssignedAutomatically() {
+        Invoice firstInvoice = new Invoice();
+        Invoice secondInvoice = new Invoice();
+
+        Assert.assertEquals(
+                firstInvoice.getNumber() + 1,
+                secondInvoice.getNumber()
+        );
+    }
 }

From 501b6ab692a36ef679d47991c052b862b2f0b752 Mon Sep 17 00:00:00 2001
From: Aleksandra <aleksandra.paperz@email.com>
Date: Wed, 17 Jun 2026 19:35:11 +0200
Subject: [PATCH 7/9] Drukowanie faktury

---
 .../java/pl/edu/agh/mwo/invoice/Invoice.java  | 30 +++++++++++++++++--
 .../pl/edu/agh/mwo/invoice/InvoiceTest.java   | 23 +++++++++++++-
 2 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
index c756ee549..26011d98e 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
@@ -1,7 +1,7 @@
 package pl.edu.agh.mwo.invoice;
 
 import java.math.BigDecimal;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.Map;
 
 import pl.edu.agh.mwo.invoice.product.Product;
@@ -9,7 +9,7 @@
 public class Invoice {
     private static int nextNumber = 1;
     private final int number;
-    private final Map<Product, Integer> products = new HashMap<Product, Integer>();
+    private final Map<Product, Integer> products = new LinkedHashMap<Product, Integer>();
 
     public Invoice() {
         number = nextNumber++;
@@ -19,6 +19,32 @@ public int getNumber() {
         return number;
     }
 
+    public String getPrintout() {
+        StringBuilder printout = new StringBuilder();
+        String separator = System.lineSeparator();
+
+        printout.append("Numer faktury: ")
+                .append(number)
+                .append(separator);
+
+        for (Map.Entry<Product, Integer> entry : products.entrySet()) {
+            Product product = entry.getKey();
+            Integer quantity = entry.getValue();
+
+            printout.append(product.getName())
+                    .append(", ")
+                    .append(quantity)
+                    .append(" szt., ")
+                    .append(product.getPrice())
+                    .append(separator);
+        }
+
+        printout.append("Liczba pozycji: ")
+                .append(products.size());
+
+        return printout.toString();
+    }
+
     public void addProduct(Product product) {
         addProduct(product, 1);
     }
diff --git a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
index 13ac02a96..8607017c9 100644
--- a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
+++ b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
@@ -137,4 +137,25 @@ public void testInvoiceNumbersAreAssignedAutomatically() {
                 secondInvoice.getNumber()
         );
     }
-}
+
+        @Test
+        public void testInvoicePrintoutContainsProductsAndInvoiceNumber() {
+            invoice.addProduct(
+                    new TaxFreeProduct("Kubek", new BigDecimal("5")), 2);
+            invoice.addProduct(
+                    new DairyProduct("Ser", new BigDecimal("10")), 3);
+
+            String separator = System.lineSeparator();
+
+            String expected = "Numer faktury: "
+                    + invoice.getNumber()
+                    + separator
+                    + "Kubek, 2 szt., 5"
+                    + separator
+                    + "Ser, 3 szt., 10"
+                    + separator
+                    + "Liczba pozycji: 2";
+
+            Assert.assertEquals(expected, invoice.getPrintout());
+        }
+    }

From b3b65a5529278d3cff0773855aafd5be53612e1d Mon Sep 17 00:00:00 2001
From: Aleksandra <aleksandra.paperz@email.com>
Date: Wed, 17 Jun 2026 21:31:03 +0200
Subject: [PATCH 8/9] =?UTF-8?q?Duplikaty=20produkt=C3=B3w?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/pl/edu/agh/mwo/invoice/Invoice.java  |  9 ++++++-
 .../edu/agh/mwo/invoice/product/Product.java  | 25 +++++++++++++++++++
 .../pl/edu/agh/mwo/invoice/InvoiceTest.java   | 23 +++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
index 26011d98e..9df7f3e97 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/Invoice.java
@@ -53,7 +53,14 @@ public void addProduct(Product product, Integer quantity) {
         if (product == null || quantity <= 0) {
             throw new IllegalArgumentException();
         }
-        products.put(product, quantity);
+
+        Integer currentQuantity = products.get(product);
+
+        if (currentQuantity == null) {
+            products.put(product, quantity);
+        } else {
+            products.put(product, currentQuantity + quantity);
+        }
     }
 
     public BigDecimal getNetTotal() {
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java b/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
index cd0f86a48..6ceba79d1 100644
--- a/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
+++ b/src/main/java/pl/edu/agh/mwo/invoice/product/Product.java
@@ -1,6 +1,7 @@
 package pl.edu.agh.mwo.invoice.product;
 
 import java.math.BigDecimal;
+import java.util.Objects;
 
 public abstract class Product {
     private final String name;
@@ -34,4 +35,28 @@ public BigDecimal getTaxPercent() {
     public BigDecimal getPriceWithTax() {
         return price.multiply(taxPercent).add(price);
     }
+
+    @Override
+    public boolean equals(Object object) {
+        if (this == object) {
+            return true;
+        }
+
+        if (object == null || getClass() != object.getClass()) {
+            return false;
+        }
+
+        Product product = (Product) object;
+
+        return Objects.equals(getName(), product.getName())
+                && getPrice().compareTo(product.getPrice()) == 0;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(
+                getClass(),
+                getName(),
+                getPrice().stripTrailingZeros());
+    }
 }
diff --git a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
index 8607017c9..1b68b87f0 100644
--- a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
+++ b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
@@ -158,4 +158,27 @@ public void testInvoicePrintoutContainsProductsAndInvoiceNumber() {
 
             Assert.assertEquals(expected, invoice.getPrintout());
         }
+
+    @Test
+    public void testAddingEquivalentProductsIncreasesQuantity() {
+        Product firstMug = new TaxFreeProduct(
+                "Kubek", new BigDecimal("5"));
+
+        Product secondMug = new TaxFreeProduct(
+                "Kubek", new BigDecimal("5.00"));
+
+        invoice.addProduct(firstMug, 2);
+        invoice.addProduct(secondMug, 3);
+
+        String separator = System.lineSeparator();
+
+        String expected = "Numer faktury: "
+                + invoice.getNumber()
+                + separator
+                + "Kubek, 5 szt., 5"
+                + separator
+                + "Liczba pozycji: 1";
+
+        Assert.assertEquals(expected, invoice.getPrintout());
+    }
     }

From cb0bb2a89023da04fd8a92b59dfc7813c680b0dd Mon Sep 17 00:00:00 2001
From: Aleksandra <aleksandra.paperz@email.com>
Date: Wed, 17 Jun 2026 21:49:02 +0200
Subject: [PATCH 9/9] VAT

---
 .../agh/mwo/invoice/product/BottleOfWine.java | 18 +++++++++++++++
 .../agh/mwo/invoice/product/FuelCanister.java | 18 +++++++++++++++
 .../pl/edu/agh/mwo/invoice/InvoiceTest.java   | 22 +++++++++++++++++++
 3 files changed, 58 insertions(+)
 create mode 100644 src/main/java/pl/edu/agh/mwo/invoice/product/BottleOfWine.java
 create mode 100644 src/main/java/pl/edu/agh/mwo/invoice/product/FuelCanister.java

diff --git a/src/main/java/pl/edu/agh/mwo/invoice/product/BottleOfWine.java b/src/main/java/pl/edu/agh/mwo/invoice/product/BottleOfWine.java
new file mode 100644
index 000000000..933fd3e05
--- /dev/null
+++ b/src/main/java/pl/edu/agh/mwo/invoice/product/BottleOfWine.java
@@ -0,0 +1,18 @@
+package pl.edu.agh.mwo.invoice.product;
+
+import java.math.BigDecimal;
+
+public class BottleOfWine extends OtherProduct {
+
+    private static final BigDecimal EXCISE_DUTY =
+            new BigDecimal("5.56");
+
+    public BottleOfWine(String name, BigDecimal price) {
+        super(name, price);
+    }
+
+    @Override
+    public BigDecimal getPriceWithTax() {
+        return super.getPriceWithTax().add(EXCISE_DUTY);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/pl/edu/agh/mwo/invoice/product/FuelCanister.java b/src/main/java/pl/edu/agh/mwo/invoice/product/FuelCanister.java
new file mode 100644
index 000000000..7b24b312b
--- /dev/null
+++ b/src/main/java/pl/edu/agh/mwo/invoice/product/FuelCanister.java
@@ -0,0 +1,18 @@
+package pl.edu.agh.mwo.invoice.product;
+
+import java.math.BigDecimal;
+
+public class FuelCanister extends TaxFreeProduct {
+
+    private static final BigDecimal EXCISE_DUTY =
+            new BigDecimal("5.56");
+
+    public FuelCanister(String name, BigDecimal price) {
+        super(name, price);
+    }
+
+    @Override
+    public BigDecimal getPriceWithTax() {
+        return super.getPriceWithTax().add(EXCISE_DUTY);
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
index 1b68b87f0..f15ad2c48 100644
--- a/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
+++ b/src/test/java/pl/edu/agh/mwo/invoice/InvoiceTest.java
@@ -12,6 +12,8 @@
 import pl.edu.agh.mwo.invoice.product.OtherProduct;
 import pl.edu.agh.mwo.invoice.product.Product;
 import pl.edu.agh.mwo.invoice.product.TaxFreeProduct;
+import pl.edu.agh.mwo.invoice.product.BottleOfWine;
+import pl.edu.agh.mwo.invoice.product.FuelCanister;
 
 public class InvoiceTest {
     private Invoice invoice;
@@ -181,4 +183,24 @@ public void testAddingEquivalentProductsIncreasesQuantity() {
 
         Assert.assertEquals(expected, invoice.getPrintout());
     }
+
+    @Test
+    public void testBottleOfWineIncludesVatAndExciseDuty() {
+        invoice.addProduct(
+                new BottleOfWine("Wino", new BigDecimal("10")));
+
+        Assert.assertThat(
+                new BigDecimal("7.86"),
+                Matchers.comparesEqualTo(invoice.getTaxTotal()));
+    }
+
+    @Test
+    public void testFuelCanisterIncludesOnlyExciseDuty() {
+        invoice.addProduct(
+                new FuelCanister("Paliwo", new BigDecimal("10")));
+
+        Assert.assertThat(
+                new BigDecimal("5.56"),
+                Matchers.comparesEqualTo(invoice.getTaxTotal()));
+    }
     }