From 5e88fd7441ec8edbb7f1c08dac2829e1398b7da6 Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:01:02 +0200
Subject: [PATCH 01/10] Extending Collection-Builders to have constructors with
 initial values

---
 .../core/builders/ArrayListBuilder.java         | 14 ++++++++++++++
 .../builders/core/builders/HashMapBuilder.java  | 14 ++++++++++++++
 .../builders/core/builders/HashSetBuilder.java  | 17 +++++++++++++++--
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/core/src/main/java/org/javahelpers/simple/builders/core/builders/ArrayListBuilder.java b/core/src/main/java/org/javahelpers/simple/builders/core/builders/ArrayListBuilder.java
index 6b5d13d6..8d94a172 100644
--- a/core/src/main/java/org/javahelpers/simple/builders/core/builders/ArrayListBuilder.java
+++ b/core/src/main/java/org/javahelpers/simple/builders/core/builders/ArrayListBuilder.java
@@ -36,6 +36,20 @@
 public class ArrayListBuilder<T> {
   private final List<T> mList = new ArrayList<>();
 
+  /** Creates an empty ArrayListBuilder. */
+  public ArrayListBuilder() {}
+
+  /**
+   * Creates an ArrayListBuilder initialized with the elements from the given list.
+   *
+   * @param initialList list to initialize from
+   */
+  public ArrayListBuilder(List<T> initialList) {
+    if (initialList != null) {
+      mList.addAll(initialList);
+    }
+  }
+
   /**
    * Appends the element to the end of the internal list. Calling add-function on inner ArrayList
    * field.
diff --git a/core/src/main/java/org/javahelpers/simple/builders/core/builders/HashMapBuilder.java b/core/src/main/java/org/javahelpers/simple/builders/core/builders/HashMapBuilder.java
index f3dfc190..e66e41ad 100644
--- a/core/src/main/java/org/javahelpers/simple/builders/core/builders/HashMapBuilder.java
+++ b/core/src/main/java/org/javahelpers/simple/builders/core/builders/HashMapBuilder.java
@@ -37,6 +37,20 @@
 public class HashMapBuilder<K, V> {
   private final Map<K, V> mMap = new HashMap<>();
 
+  /** Creates an empty HashMapBuilder. */
+  public HashMapBuilder() {}
+
+  /**
+   * Creates a HashMapBuilder initialized with the mappings from the given map.
+   *
+   * @param initialMap map to initialize from
+   */
+  public HashMapBuilder(Map<K, V> initialMap) {
+    if (initialMap != null) {
+      mMap.putAll(initialMap);
+    }
+  }
+
   /**
    * Associates the specified value with the specified key in this map. Using an inner HashMap
    * implementation. If the key already exists in the map, the old value is replaced.
diff --git a/core/src/main/java/org/javahelpers/simple/builders/core/builders/HashSetBuilder.java b/core/src/main/java/org/javahelpers/simple/builders/core/builders/HashSetBuilder.java
index 57448b23..d49dcb4f 100644
--- a/core/src/main/java/org/javahelpers/simple/builders/core/builders/HashSetBuilder.java
+++ b/core/src/main/java/org/javahelpers/simple/builders/core/builders/HashSetBuilder.java
@@ -36,9 +36,22 @@
 public class HashSetBuilder<T> {
   private final Set<T> mSet = new HashSet<>();
 
+  /** Creates an empty HashSetBuilder. */
+  public HashSetBuilder() {}
+
+  /**
+   * Creates a HashSetBuilder initialized with the elements from the given set.
+   *
+   * @param initialSet set to initialize from
+   */
+  public HashSetBuilder(Set<T> initialSet) {
+    if (initialSet != null) {
+      mSet.addAll(initialSet);
+    }
+  }
+
   /**
-   * Adds the specified element to this set if it is not already present. Calling add-function on
-   * inner HashSet field.
+   * Appends the element to the internal set. Calling add-function on inner HashSet field.
    *
    * @param element element to be appended
    * @return current instance of ArrayListBuilder for using in stream-notation

From 597254ee075041cd3385eb88ea3d81b96737be6a Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:03:10 +0200
Subject: [PATCH 02/10] Reusing values in consumers and builders which are
 providing a builder via consumer

---
 .../builders/processor/util/BuilderDefinitionCreator.java   | 4 ++--
 .../simple/builders/processor/BuilderProcessorTest.java     | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
index 0cbf7220..1960942a 100644
--- a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
+++ b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
@@ -489,7 +489,7 @@ private static MethodDto createFieldConsumer(String fieldName, TypeName fieldTyp
     methodDto.setMethodType(MethodTypes.CONSUMER);
     methodDto.setCode(
         """
-        $helperType:T consumer = new $helperType:T();
+        $helperType:T consumer = this.$fieldName:N.isChanged() ? this.$fieldName:N.value() : new $helperType:T();
         $dtoMethodParam:N.accept(consumer);
         this.$fieldName:N = $builderFieldWrapper:T.changedValue(consumer);
         return this;
@@ -545,7 +545,7 @@ private static MethodDto createFieldConsumerWithBuilder(String fieldName, TypeNa
     methodDto.setMethodType(MethodTypes.CONSUMER_BY_BUILDER);
     methodDto.setCode(
         """
-        $helperType:T builder = new $helperType:T();
+        $helperType:T builder = this.$fieldName:N.isChanged() ? new $helperType:T(this.$fieldName:N.value()) : new $helperType:T();
         $dtoMethodParam:N.accept(builder);
         this.$fieldName:N = $builderFieldWrapper:T.changedValue(builder.build());
         return this;
diff --git a/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java b/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
index 6db98c43..df1c0095 100644
--- a/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
+++ b/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
@@ -454,7 +454,7 @@ public Address() {}
         "public RequiredCustomTypeViaConstructorBuilder address(Supplier<Address> addressSupplier)",
         // Consumer method for constructor field (the key coverage addition!)
         "public RequiredCustomTypeViaConstructorBuilder address(Consumer<Address> addressConsumer)",
-        "Address consumer = new Address();",
+        "Address consumer = this.address.isChanged() ? this.address.value() : new Address();",
         "addressConsumer.accept(consumer);");
   }
 
@@ -1206,7 +1206,7 @@ public HelperAnno() {}
         generatedCode,
         "private TrackedValue<HelperAnno> helper = unsetValue();",
         "helperBuilderConsumer",
-        "HelperAnnoBuilder builder = new HelperAnnoBuilder();",
+        "HelperAnnoBuilder builder = this.helper.isChanged() ? new HelperAnnoBuilder(this.helper.value()) : new HelperAnnoBuilder();",
         "helperBuilderConsumer.accept(builder);",
         "this.helper = changedValue(builder.build());");
   }
@@ -1248,7 +1248,7 @@ public HelperPlain() {}
     // Expect consumer method with local var named 'consumer' of HelperPlain
     ProcessorAsserts.assertContaining(
         generatedCode,
-        "HelperPlain consumer = new HelperPlain();",
+        "HelperPlain consumer = this.helperPlain.isChanged() ? this.helperPlain.value() : new HelperPlain();",
         "helperPlainConsumer.accept(consumer);",
         "private TrackedValue<HelperPlain> helperPlain = unsetValue();");
   }

From cde284d4c179349685349fdcf8c60a6a2f2322b4 Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:11:52 +0200
Subject: [PATCH 03/10] Extending PersonDtoBuilderTest with an example of
 extending arrays

---
 .../simple/builders/example/PersonDtoBuilderTest.java           | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java b/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
index ba234ce5..92a5cc07 100644
--- a/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
+++ b/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
@@ -38,6 +38,7 @@ void testBuilder() {
         PersonDtoBuilder.create()
             .birthdate(LocalDate.now())
             .nickNames(b -> b.add("Test1").add("Test2"))
+            .nickNames(b -> b.add("Test3").add("Test4"))
             .mannschaft(
                 mb ->
                     mb.name("Testmannschaft")
@@ -50,6 +51,7 @@ void testBuilder() {
     assertEquals("Testname", personDto.getName());
     assertNotNull(personDto.getMannschaft());
     assertEquals("Testmannschaft", personDto.getMannschaft().getName());
+    assertEquals(4, personDto.getNickNames().size());
   }
 
   private String nameSupplier() {

From aa722d0cf3cb7aaf66740395cc6ef24aee1d1c88 Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:19:30 +0200
Subject: [PATCH 04/10] Changing functionality, the value should be taken if
 already set

---
 .../simple/builders/core/util/TrackedValue.java           | 8 ++++----
 .../simple/builders/example/PersonDtoBuilderTest.java     | 1 +
 .../builders/processor/util/BuilderDefinitionCreator.java | 4 ++--
 .../simple/builders/processor/BuilderProcessorTest.java   | 6 +++---
 4 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java b/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
index 8d4f6854..251638d4 100644
--- a/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
+++ b/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
@@ -44,7 +44,7 @@
  * @param value the underlying value (may be {@code null})
  * @param isChanged whether the value was explicitly changed by the builder API
  */
-public record TrackedValue<T>(T value, boolean isChanged) {
+public record TrackedValue<T>(T value, boolean isChanged, boolean isUnset) {
 
   /**
    * Executes the provided {@link Consumer} only if this value has been explicitly changed.
@@ -65,7 +65,7 @@ public void ifChanged(Consumer<T> consumer) {
    * @return an instance with {@code value == null} and {@code isChanged == false}
    */
   public static <T> TrackedValue<T> unsetValue() {
-    return new TrackedValue<>(null, false);
+    return new TrackedValue<>(null, false, true);
   }
 
   /**
@@ -77,7 +77,7 @@ public static <T> TrackedValue<T> unsetValue() {
    * @return an instance with the given value and {@code isChanged == false}
    */
   public static <T> TrackedValue<T> initialValue(T value) {
-    return new TrackedValue<>(value, false);
+    return new TrackedValue<>(value, false, false);
   }
 
   /**
@@ -88,6 +88,6 @@ public static <T> TrackedValue<T> initialValue(T value) {
    * @return an instance with the given value and {@code isChanged == true}
    */
   public static <T> TrackedValue<T> changedValue(T value) {
-    return new TrackedValue<>(value, true);
+    return new TrackedValue<>(value, true, false);
   }
 }
diff --git a/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java b/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
index 92a5cc07..fffdd113 100644
--- a/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
+++ b/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
@@ -45,6 +45,7 @@ void testBuilder() {
                         .sponsoren(
                             sb -> sb.add(SponsorDtoBuilder.create().name("TestSponsor").build())))
             .name(this::nameSupplier)
+            .mannschaft(mb -> mb.sponsoren(sb -> sb.add(SponsorDtoBuilder.create().name("TestSponsor2").build())))
             .build();
     assertNotNull(personDto);
     assertNotNull(personDto.getBirthdate());
diff --git a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
index 1960942a..a81c865b 100644
--- a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
+++ b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
@@ -489,7 +489,7 @@ private static MethodDto createFieldConsumer(String fieldName, TypeName fieldTyp
     methodDto.setMethodType(MethodTypes.CONSUMER);
     methodDto.setCode(
         """
-        $helperType:T consumer = this.$fieldName:N.isChanged() ? this.$fieldName:N.value() : new $helperType:T();
+        $helperType:T consumer = !this.$fieldName:N.isUnset() ? this.$fieldName:N.value() : new $helperType:T();
         $dtoMethodParam:N.accept(consumer);
         this.$fieldName:N = $builderFieldWrapper:T.changedValue(consumer);
         return this;
@@ -545,7 +545,7 @@ private static MethodDto createFieldConsumerWithBuilder(String fieldName, TypeNa
     methodDto.setMethodType(MethodTypes.CONSUMER_BY_BUILDER);
     methodDto.setCode(
         """
-        $helperType:T builder = this.$fieldName:N.isChanged() ? new $helperType:T(this.$fieldName:N.value()) : new $helperType:T();
+        $helperType:T builder = !this.$fieldName:N.isUnset() ? new $helperType:T(this.$fieldName:N.value()) : new $helperType:T();
         $dtoMethodParam:N.accept(builder);
         this.$fieldName:N = $builderFieldWrapper:T.changedValue(builder.build());
         return this;
diff --git a/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java b/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
index df1c0095..ccf23d8a 100644
--- a/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
+++ b/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
@@ -454,7 +454,7 @@ public Address() {}
         "public RequiredCustomTypeViaConstructorBuilder address(Supplier<Address> addressSupplier)",
         // Consumer method for constructor field (the key coverage addition!)
         "public RequiredCustomTypeViaConstructorBuilder address(Consumer<Address> addressConsumer)",
-        "Address consumer = this.address.isChanged() ? this.address.value() : new Address();",
+        "Address consumer = !this.address.isUnset() ? this.address.value() : new Address();",
         "addressConsumer.accept(consumer);");
   }
 
@@ -1206,7 +1206,7 @@ public HelperAnno() {}
         generatedCode,
         "private TrackedValue<HelperAnno> helper = unsetValue();",
         "helperBuilderConsumer",
-        "HelperAnnoBuilder builder = this.helper.isChanged() ? new HelperAnnoBuilder(this.helper.value()) : new HelperAnnoBuilder();",
+        "HelperAnnoBuilder builder = !this.helper.isUnset() ? new HelperAnnoBuilder(this.helper.value()) : new HelperAnnoBuilder();",
         "helperBuilderConsumer.accept(builder);",
         "this.helper = changedValue(builder.build());");
   }
@@ -1248,7 +1248,7 @@ public HelperPlain() {}
     // Expect consumer method with local var named 'consumer' of HelperPlain
     ProcessorAsserts.assertContaining(
         generatedCode,
-        "HelperPlain consumer = this.helperPlain.isChanged() ? this.helperPlain.value() : new HelperPlain();",
+        "HelperPlain consumer = !this.helperPlain.isUnset() ? this.helperPlain.value() : new HelperPlain();",
         "helperPlainConsumer.accept(consumer);",
         "private TrackedValue<HelperPlain> helperPlain = unsetValue();");
   }

From 15d6c3d51531d366af6dc7879f29ca0a7b81820b Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:38:19 +0200
Subject: [PATCH 05/10] Fixing handling of initial values

---
 .../builders/core/util/TrackedValue.java      | 23 +++++++++++--------
 .../util/BuilderDefinitionCreator.java        |  4 ++--
 .../processor/util/JavaCodeGenerator.java     |  4 ++--
 .../processor/BuilderProcessorTest.java       | 12 +++++-----
 4 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java b/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
index 251638d4..ff10fd1e 100644
--- a/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
+++ b/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
@@ -43,17 +43,18 @@
  * @param <T> the value type
  * @param value the underlying value (may be {@code null})
  * @param isChanged whether the value was explicitly changed by the builder API
+ * @param isInitial whether the value is an initial value from an existing instance
  */
-public record TrackedValue<T>(T value, boolean isChanged, boolean isUnset) {
+public record TrackedValue<T>(T value, boolean isChanged, boolean isInitial) {
 
   /**
-   * Executes the provided {@link Consumer} only if this value has been explicitly changed.
+   * Executes the provided {@link Consumer} only if this value has been set (initial value or
+   * changed).
    *
-   * @param consumer action to perform with the current {@link #value()} when {@link #isChanged()}
-   *     is {@code true}
+   * @param consumer action to perform with the current {@link #value()}
    */
-  public void ifChanged(Consumer<T> consumer) {
-    if (isChanged) {
+  public void ifSet(Consumer<T> consumer) {
+    if (isChanged || isInitial) {
       consumer.accept(value);
     }
   }
@@ -62,10 +63,11 @@ public void ifChanged(Consumer<T> consumer) {
    * Creates a tracked value representing an unset state (no change made).
    *
    * @param <T> the value type
-   * @return an instance with {@code value == null} and {@code isChanged == false}
+   * @return an instance with {@code value == null}, {@code isChanged == false}, and {@code
+   *     isInitial == false}
    */
   public static <T> TrackedValue<T> unsetValue() {
-    return new TrackedValue<>(null, false, true);
+    return new TrackedValue<>(null, false, false);
   }
 
   /**
@@ -74,10 +76,11 @@ public static <T> TrackedValue<T> unsetValue() {
    *
    * @param <T> the value type
    * @param value the initial value (may be {@code null})
-   * @return an instance with the given value and {@code isChanged == false}
+   * @return an instance with the given value, {@code isChanged == false}, and {@code isInitial ==
+   *     true}
    */
   public static <T> TrackedValue<T> initialValue(T value) {
-    return new TrackedValue<>(value, false, false);
+    return new TrackedValue<>(value, false, true);
   }
 
   /**
diff --git a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
index a81c865b..d9a8a327 100644
--- a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
+++ b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
@@ -489,7 +489,7 @@ private static MethodDto createFieldConsumer(String fieldName, TypeName fieldTyp
     methodDto.setMethodType(MethodTypes.CONSUMER);
     methodDto.setCode(
         """
-        $helperType:T consumer = !this.$fieldName:N.isUnset() ? this.$fieldName:N.value() : new $helperType:T();
+        $helperType:T consumer = this.$fieldName:N.ifSet() ? this.$fieldName:N.value() : new $helperType:T();
         $dtoMethodParam:N.accept(consumer);
         this.$fieldName:N = $builderFieldWrapper:T.changedValue(consumer);
         return this;
@@ -545,7 +545,7 @@ private static MethodDto createFieldConsumerWithBuilder(String fieldName, TypeNa
     methodDto.setMethodType(MethodTypes.CONSUMER_BY_BUILDER);
     methodDto.setCode(
         """
-        $helperType:T builder = !this.$fieldName:N.isUnset() ? new $helperType:T(this.$fieldName:N.value()) : new $helperType:T();
+        $helperType:T builder = this.$fieldName:N.ifSet() ? new $helperType:T(this.$fieldName:N.value()) : new $helperType:T();
         $dtoMethodParam:N.accept(builder);
         this.$fieldName:N = $builderFieldWrapper:T.changedValue(builder.build());
         return this;
diff --git a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/JavaCodeGenerator.java b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/JavaCodeGenerator.java
index 2a99207b..5d261417 100644
--- a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/JavaCodeGenerator.java
+++ b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/JavaCodeGenerator.java
@@ -281,9 +281,9 @@ private MethodSpec createMethodBuild(
       mb.addStatement("$1T result = new $2T<>($3L)", returnType, dtoBaseClass, ctorArgs);
     }
 
-    // Apply setter-based fields only when changed
+    // Apply setter-based fields only when set
     for (FieldDto f : setterFields) {
-      mb.addStatement("this.$N.ifChanged(result::$N)", f.getFieldName(), f.getSetterName());
+      mb.addStatement("this.$N.ifSet(result::$N)", f.getFieldName(), f.getSetterName());
     }
     mb.addStatement("return result");
     return mb.build();
diff --git a/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java b/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
index ccf23d8a..eb66b85f 100644
--- a/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
+++ b/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
@@ -201,7 +201,7 @@ void shouldHandleFieldsOfConstructorAndSetters() {
         "public CtorAndSetterBuilder a(int a)", // helpermethod for constructor param
         "public CtorAndSetterBuilder a(Supplier<Integer> aSupplier)", // supplier for constructor
         "CtorAndSetter result = new CtorAndSetter(this.a.value());",
-        "this.name.ifChanged(result::setName);");
+        "this.name.ifSet(result::setName);");
   }
 
   @Test
@@ -247,7 +247,7 @@ void shouldPreferConstructorOverSetterWhenBothExist() {
         "public CtorAndSetterSameFieldBuilder name(String name)",
         // Expectations on build function
         "CtorAndSetterSameField result = new CtorAndSetterSameField(this.a.value());",
-        "this.name.ifChanged(result::setName);");
+        "this.name.ifSet(result::setName);");
     // expect no setter application for 'a' on build-function
     ProcessorAsserts.assertNotContaining(generatedCode, "result.setA(this.a);");
   }
@@ -454,7 +454,7 @@ public Address() {}
         "public RequiredCustomTypeViaConstructorBuilder address(Supplier<Address> addressSupplier)",
         // Consumer method for constructor field (the key coverage addition!)
         "public RequiredCustomTypeViaConstructorBuilder address(Consumer<Address> addressConsumer)",
-        "Address consumer = !this.address.isUnset() ? this.address.value() : new Address();",
+        "Address consumer = this.address.ifSet() ? this.address.value() : new Address();",
         "addressConsumer.accept(consumer);");
   }
 
@@ -882,7 +882,7 @@ void shouldGenerateBuildOverrideAndReturnAnInstanceWithCalledSetters() {
         @Override
         public BuildDoc build() {
             BuildDoc result = new BuildDoc();
-            this.x.ifChanged(result::setX);
+            this.x.ifSet(result::setX);
             return result;
         }
         """);
@@ -1206,7 +1206,7 @@ public HelperAnno() {}
         generatedCode,
         "private TrackedValue<HelperAnno> helper = unsetValue();",
         "helperBuilderConsumer",
-        "HelperAnnoBuilder builder = !this.helper.isUnset() ? new HelperAnnoBuilder(this.helper.value()) : new HelperAnnoBuilder();",
+        "HelperAnnoBuilder builder = this.helper.ifSet() ? new HelperAnnoBuilder(this.helper.value()) : new HelperAnnoBuilder();",
         "helperBuilderConsumer.accept(builder);",
         "this.helper = changedValue(builder.build());");
   }
@@ -1248,7 +1248,7 @@ public HelperPlain() {}
     // Expect consumer method with local var named 'consumer' of HelperPlain
     ProcessorAsserts.assertContaining(
         generatedCode,
-        "HelperPlain consumer = !this.helperPlain.isUnset() ? this.helperPlain.value() : new HelperPlain();",
+        "HelperPlain consumer = this.helperPlain.ifSet() ? this.helperPlain.value() : new HelperPlain();",
         "helperPlainConsumer.accept(consumer);",
         "private TrackedValue<HelperPlain> helperPlain = unsetValue();");
   }

From f56ea738f35dae5452e6779f82e7b1938ea2bac3 Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:40:49 +0200
Subject: [PATCH 06/10] Fixing code to use one helper function instead of two

---
 .../simple/builders/core/util/TrackedValue.java       | 11 ++++++++++-
 .../processor/util/BuilderDefinitionCreator.java      |  4 ++--
 .../builders/processor/BuilderProcessorTest.java      |  6 +++---
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java b/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
index ff10fd1e..8cc2a919 100644
--- a/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
+++ b/core/src/main/java/org/javahelpers/simple/builders/core/util/TrackedValue.java
@@ -47,6 +47,15 @@
  */
 public record TrackedValue<T>(T value, boolean isChanged, boolean isInitial) {
 
+  /**
+   * Checks if this value has been set (either as initial value or changed).
+   *
+   * @return true if the value is set (initial or changed), false if unset
+   */
+  public boolean isSet() {
+    return isChanged || isInitial;
+  }
+
   /**
    * Executes the provided {@link Consumer} only if this value has been set (initial value or
    * changed).
@@ -54,7 +63,7 @@ public record TrackedValue<T>(T value, boolean isChanged, boolean isInitial) {
    * @param consumer action to perform with the current {@link #value()}
    */
   public void ifSet(Consumer<T> consumer) {
-    if (isChanged || isInitial) {
+    if (isSet()) {
       consumer.accept(value);
     }
   }
diff --git a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
index d9a8a327..1499b520 100644
--- a/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
+++ b/processor/src/main/java/org/javahelpers/simple/builders/processor/util/BuilderDefinitionCreator.java
@@ -489,7 +489,7 @@ private static MethodDto createFieldConsumer(String fieldName, TypeName fieldTyp
     methodDto.setMethodType(MethodTypes.CONSUMER);
     methodDto.setCode(
         """
-        $helperType:T consumer = this.$fieldName:N.ifSet() ? this.$fieldName:N.value() : new $helperType:T();
+        $helperType:T consumer = this.$fieldName:N.isSet() ? this.$fieldName:N.value() : new $helperType:T();
         $dtoMethodParam:N.accept(consumer);
         this.$fieldName:N = $builderFieldWrapper:T.changedValue(consumer);
         return this;
@@ -545,7 +545,7 @@ private static MethodDto createFieldConsumerWithBuilder(String fieldName, TypeNa
     methodDto.setMethodType(MethodTypes.CONSUMER_BY_BUILDER);
     methodDto.setCode(
         """
-        $helperType:T builder = this.$fieldName:N.ifSet() ? new $helperType:T(this.$fieldName:N.value()) : new $helperType:T();
+        $helperType:T builder = this.$fieldName:N.isSet() ? new $helperType:T(this.$fieldName:N.value()) : new $helperType:T();
         $dtoMethodParam:N.accept(builder);
         this.$fieldName:N = $builderFieldWrapper:T.changedValue(builder.build());
         return this;
diff --git a/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java b/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
index eb66b85f..c86be7db 100644
--- a/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
+++ b/processor/src/test/java/org/javahelpers/simple/builders/processor/BuilderProcessorTest.java
@@ -454,7 +454,7 @@ public Address() {}
         "public RequiredCustomTypeViaConstructorBuilder address(Supplier<Address> addressSupplier)",
         // Consumer method for constructor field (the key coverage addition!)
         "public RequiredCustomTypeViaConstructorBuilder address(Consumer<Address> addressConsumer)",
-        "Address consumer = this.address.ifSet() ? this.address.value() : new Address();",
+        "Address consumer = this.address.isSet() ? this.address.value() : new Address();",
         "addressConsumer.accept(consumer);");
   }
 
@@ -1206,7 +1206,7 @@ public HelperAnno() {}
         generatedCode,
         "private TrackedValue<HelperAnno> helper = unsetValue();",
         "helperBuilderConsumer",
-        "HelperAnnoBuilder builder = this.helper.ifSet() ? new HelperAnnoBuilder(this.helper.value()) : new HelperAnnoBuilder();",
+        "HelperAnnoBuilder builder = this.helper.isSet() ? new HelperAnnoBuilder(this.helper.value()) : new HelperAnnoBuilder();",
         "helperBuilderConsumer.accept(builder);",
         "this.helper = changedValue(builder.build());");
   }
@@ -1248,7 +1248,7 @@ public HelperPlain() {}
     // Expect consumer method with local var named 'consumer' of HelperPlain
     ProcessorAsserts.assertContaining(
         generatedCode,
-        "HelperPlain consumer = this.helperPlain.ifSet() ? this.helperPlain.value() : new HelperPlain();",
+        "HelperPlain consumer = this.helperPlain.isSet() ? this.helperPlain.value() : new HelperPlain();",
         "helperPlainConsumer.accept(consumer);",
         "private TrackedValue<HelperPlain> helperPlain = unsetValue();");
   }

From 4efd6ee9182e31a44be46fe59f3e88d01c53b6a5 Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:42:47 +0200
Subject: [PATCH 07/10] Adding assert for the rechange of mannschaft by builder

---
 .../simple/builders/example/PersonDtoBuilderTest.java            | 1 +
 1 file changed, 1 insertion(+)

diff --git a/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java b/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
index fffdd113..75e9ab50 100644
--- a/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
+++ b/example/src/test/java/org/javahelpers/simple/builders/example/PersonDtoBuilderTest.java
@@ -53,6 +53,7 @@ void testBuilder() {
     assertNotNull(personDto.getMannschaft());
     assertEquals("Testmannschaft", personDto.getMannschaft().getName());
     assertEquals(4, personDto.getNickNames().size());
+    assertEquals(2, personDto.getMannschaft().getSponsoren().size());
   }
 
   private String nameSupplier() {

From 1dee9cf27de80a5d03910bd59d249d739a8e838b Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:51:23 +0200
Subject: [PATCH 08/10] Adding tests in core-module

---
 core/pom.xml                                  |  16 ++
 .../core/builders/ArrayListBuilderTest.java   | 139 ++++++++++++
 .../core/builders/HashMapBuilderTest.java     | 172 ++++++++++++++
 .../core/builders/HashSetBuilderTest.java     | 151 +++++++++++++
 .../builders/core/util/TrackedValueTest.java  | 210 ++++++++++++++++++
 5 files changed, 688 insertions(+)
 create mode 100644 core/src/test/java/org/javahelpers/simple/builders/core/builders/ArrayListBuilderTest.java
 create mode 100644 core/src/test/java/org/javahelpers/simple/builders/core/builders/HashMapBuilderTest.java
 create mode 100644 core/src/test/java/org/javahelpers/simple/builders/core/builders/HashSetBuilderTest.java
 create mode 100644 core/src/test/java/org/javahelpers/simple/builders/core/util/TrackedValueTest.java

diff --git a/core/pom.xml b/core/pom.xml
index f3c0f8e2..a57bb7b9 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -64,6 +64,9 @@
     <!-- Maven Central Publishing -->
     <central.autoPublish>false</central.autoPublish>
     
+    <!-- Dependency Versions -->
+    <junit-jupiter.version>6.0.0</junit-jupiter.version>
+    
     <!-- Plugin Versions -->
     <plugin.central.publishing.version>0.9.0</plugin.central.publishing.version>
     <plugin.code-format.version>2.29</plugin.code-format.version>
@@ -76,6 +79,19 @@
   </properties>
 
   <dependencies>
+    <!-- Test Dependencies -->
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-api</artifactId>
+      <version>${junit-jupiter.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-engine</artifactId>
+      <version>${junit-jupiter.version}</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>
diff --git a/core/src/test/java/org/javahelpers/simple/builders/core/builders/ArrayListBuilderTest.java b/core/src/test/java/org/javahelpers/simple/builders/core/builders/ArrayListBuilderTest.java
new file mode 100644
index 00000000..47603b17
--- /dev/null
+++ b/core/src/test/java/org/javahelpers/simple/builders/core/builders/ArrayListBuilderTest.java
@@ -0,0 +1,139 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2025 Andreas Igel
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.javahelpers.simple.builders.core.builders;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+class ArrayListBuilderTest {
+
+  @Test
+  void shouldCreateEmptyBuilder() {
+    ArrayListBuilder<String> builder = new ArrayListBuilder<>();
+    List<String> result = builder.build();
+
+    assertNotNull(result);
+    assertTrue(result.isEmpty());
+  }
+
+  @Test
+  void shouldCreateBuilderWithInitialList() {
+    List<String> initial = Arrays.asList("item1", "item2", "item3");
+
+    ArrayListBuilder<String> builder = new ArrayListBuilder<>(initial);
+    List<String> result = builder.build();
+
+    assertNotNull(result);
+    assertEquals(3, result.size());
+    assertEquals("item1", result.get(0));
+    assertEquals("item2", result.get(1));
+    assertEquals("item3", result.get(2));
+  }
+
+  @Test
+  void shouldHandleNullInitialList() {
+    ArrayListBuilder<String> builder = new ArrayListBuilder<>(null);
+    List<String> result = builder.build();
+
+    assertNotNull(result);
+    assertTrue(result.isEmpty());
+  }
+
+  @Test
+  void shouldAllowAddingToInitializedList() {
+    List<String> initial = Arrays.asList("item1", "item2");
+
+    ArrayListBuilder<String> builder = new ArrayListBuilder<>(initial);
+    builder.add("item3").add("item4");
+    List<String> result = builder.build();
+
+    assertNotNull(result);
+    assertEquals(4, result.size());
+    assertEquals("item1", result.get(0));
+    assertEquals("item2", result.get(1));
+    assertEquals("item3", result.get(2));
+    assertEquals("item4", result.get(3));
+  }
+
+  @Test
+  void shouldAddSingleElement() {
+    ArrayListBuilder<String> builder = new ArrayListBuilder<>();
+    builder.add("test");
+    List<String> result = builder.build();
+
+    assertEquals(1, result.size());
+    assertEquals("test", result.get(0));
+  }
+
+  @Test
+  void shouldAddMultipleElements() {
+    ArrayListBuilder<String> builder = new ArrayListBuilder<>();
+    builder.add("first").add("second").add("third");
+    List<String> result = builder.build();
+
+    assertEquals(3, result.size());
+    assertEquals("first", result.get(0));
+    assertEquals("second", result.get(1));
+    assertEquals("third", result.get(2));
+  }
+
+  @Test
+  void shouldAddAllFromCollection() {
+    ArrayListBuilder<Integer> builder = new ArrayListBuilder<>();
+    builder.addAll(Arrays.asList(1, 2, 3));
+    List<Integer> result = builder.build();
+
+    assertEquals(3, result.size());
+    assertEquals(1, result.get(0));
+    assertEquals(2, result.get(1));
+    assertEquals(3, result.get(2));
+  }
+
+  @Test
+  void shouldChainAddAndAddAll() {
+    ArrayListBuilder<String> builder = new ArrayListBuilder<>();
+    builder.add("first").addAll(Arrays.asList("second", "third")).add("fourth");
+    List<String> result = builder.build();
+
+    assertEquals(4, result.size());
+    assertEquals("first", result.get(0));
+    assertEquals("second", result.get(1));
+    assertEquals("third", result.get(2));
+    assertEquals("fourth", result.get(3));
+  }
+
+  @Test
+  void shouldReturnThisForFluentInterface() {
+    ArrayListBuilder<String> builder = new ArrayListBuilder<>();
+    ArrayListBuilder<String> result = builder.add("test");
+
+    assertEquals(builder, result);
+  }
+}
diff --git a/core/src/test/java/org/javahelpers/simple/builders/core/builders/HashMapBuilderTest.java b/core/src/test/java/org/javahelpers/simple/builders/core/builders/HashMapBuilderTest.java
new file mode 100644
index 00000000..9b47c95f
--- /dev/null
+++ b/core/src/test/java/org/javahelpers/simple/builders/core/builders/HashMapBuilderTest.java
@@ -0,0 +1,172 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2025 Andreas Igel
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.javahelpers.simple.builders.core.builders;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class HashMapBuilderTest {
+
+  @Test
+  void shouldCreateEmptyBuilder() {
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>();
+    Map<String, Integer> result = builder.build();
+
+    assertNotNull(result);
+    assertTrue(result.isEmpty());
+  }
+
+  @Test
+  void shouldCreateBuilderWithInitialMap() {
+    Map<String, Integer> initial = new HashMap<>();
+    initial.put("one", 1);
+    initial.put("two", 2);
+    initial.put("three", 3);
+
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>(initial);
+    Map<String, Integer> result = builder.build();
+
+    assertNotNull(result);
+    assertEquals(3, result.size());
+    assertEquals(1, result.get("one"));
+    assertEquals(2, result.get("two"));
+    assertEquals(3, result.get("three"));
+  }
+
+  @Test
+  void shouldHandleNullInitialMap() {
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>(null);
+    Map<String, Integer> result = builder.build();
+
+    assertNotNull(result);
+    assertTrue(result.isEmpty());
+  }
+
+  @Test
+  void shouldAllowAddingToInitializedMap() {
+    Map<String, Integer> initial = new HashMap<>();
+    initial.put("one", 1);
+    initial.put("two", 2);
+
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>(initial);
+    builder.put("three", 3).put("four", 4);
+    Map<String, Integer> result = builder.build();
+
+    assertNotNull(result);
+    assertEquals(4, result.size());
+    assertEquals(1, result.get("one"));
+    assertEquals(2, result.get("two"));
+    assertEquals(3, result.get("three"));
+    assertEquals(4, result.get("four"));
+  }
+
+  @Test
+  void shouldPutSingleEntry() {
+    HashMapBuilder<String, String> builder = new HashMapBuilder<>();
+    builder.put("key", "value");
+    Map<String, String> result = builder.build();
+
+    assertEquals(1, result.size());
+    assertEquals("value", result.get("key"));
+  }
+
+  @Test
+  void shouldPutMultipleEntries() {
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>();
+    builder.put("first", 1).put("second", 2).put("third", 3);
+    Map<String, Integer> result = builder.build();
+
+    assertEquals(3, result.size());
+    assertEquals(1, result.get("first"));
+    assertEquals(2, result.get("second"));
+    assertEquals(3, result.get("third"));
+  }
+
+  @Test
+  void shouldOverwriteExistingKey() {
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>();
+    builder.put("key", 1).put("key", 2);
+    Map<String, Integer> result = builder.build();
+
+    assertEquals(1, result.size());
+    assertEquals(2, result.get("key"));
+  }
+
+  @Test
+  void shouldPutAllFromMap() {
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>();
+    Map<String, Integer> additional = new HashMap<>();
+    additional.put("a", 1);
+    additional.put("b", 2);
+
+    builder.putAll(additional);
+    Map<String, Integer> result = builder.build();
+
+    assertEquals(2, result.size());
+    assertEquals(1, result.get("a"));
+    assertEquals(2, result.get("b"));
+  }
+
+  @Test
+  void shouldChainPutAndPutAll() {
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>();
+    Map<String, Integer> additional = new HashMap<>();
+    additional.put("two", 2);
+    additional.put("three", 3);
+
+    builder.put("one", 1).putAll(additional).put("four", 4);
+    Map<String, Integer> result = builder.build();
+
+    assertEquals(4, result.size());
+    assertEquals(1, result.get("one"));
+    assertEquals(2, result.get("two"));
+    assertEquals(3, result.get("three"));
+    assertEquals(4, result.get("four"));
+  }
+
+  @Test
+  void shouldHandleNullValues() {
+    HashMapBuilder<String, String> builder = new HashMapBuilder<>();
+    builder.put("key", null);
+    Map<String, String> result = builder.build();
+
+    assertEquals(1, result.size());
+    assertTrue(result.containsKey("key"));
+    assertEquals(null, result.get("key"));
+  }
+
+  @Test
+  void shouldReturnThisForFluentInterface() {
+    HashMapBuilder<String, Integer> builder = new HashMapBuilder<>();
+    HashMapBuilder<String, Integer> result = builder.put("key", 1);
+
+    assertEquals(builder, result);
+  }
+}
diff --git a/core/src/test/java/org/javahelpers/simple/builders/core/builders/HashSetBuilderTest.java b/core/src/test/java/org/javahelpers/simple/builders/core/builders/HashSetBuilderTest.java
new file mode 100644
index 00000000..883f3d24
--- /dev/null
+++ b/core/src/test/java/org/javahelpers/simple/builders/core/builders/HashSetBuilderTest.java
@@ -0,0 +1,151 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2025 Andreas Igel
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.javahelpers.simple.builders.core.builders;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+import org.junit.jupiter.api.Test;
+
+class HashSetBuilderTest {
+
+  @Test
+  void shouldCreateEmptyBuilder() {
+    HashSetBuilder<String> builder = new HashSetBuilder<>();
+    Set<String> result = builder.build();
+
+    assertNotNull(result);
+    assertTrue(result.isEmpty());
+  }
+
+  @Test
+  void shouldCreateBuilderWithInitialSet() {
+    Set<String> initial = new HashSet<>(Arrays.asList("item1", "item2", "item3"));
+
+    HashSetBuilder<String> builder = new HashSetBuilder<>(initial);
+    Set<String> result = builder.build();
+
+    assertNotNull(result);
+    assertEquals(3, result.size());
+    assertTrue(result.contains("item1"));
+    assertTrue(result.contains("item2"));
+    assertTrue(result.contains("item3"));
+  }
+
+  @Test
+  void shouldHandleNullInitialSet() {
+    HashSetBuilder<String> builder = new HashSetBuilder<>(null);
+    Set<String> result = builder.build();
+
+    assertNotNull(result);
+    assertTrue(result.isEmpty());
+  }
+
+  @Test
+  void shouldAllowAddingToInitializedSet() {
+    Set<String> initial = new HashSet<>(Arrays.asList("item1", "item2"));
+
+    HashSetBuilder<String> builder = new HashSetBuilder<>(initial);
+    builder.add("item3").add("item4");
+    Set<String> result = builder.build();
+
+    assertNotNull(result);
+    assertEquals(4, result.size());
+    assertTrue(result.contains("item1"));
+    assertTrue(result.contains("item2"));
+    assertTrue(result.contains("item3"));
+    assertTrue(result.contains("item4"));
+  }
+
+  @Test
+  void shouldAddSingleElement() {
+    HashSetBuilder<String> builder = new HashSetBuilder<>();
+    builder.add("test");
+    Set<String> result = builder.build();
+
+    assertEquals(1, result.size());
+    assertTrue(result.contains("test"));
+  }
+
+  @Test
+  void shouldAddMultipleElements() {
+    HashSetBuilder<String> builder = new HashSetBuilder<>();
+    builder.add("first").add("second").add("third");
+    Set<String> result = builder.build();
+
+    assertEquals(3, result.size());
+    assertTrue(result.contains("first"));
+    assertTrue(result.contains("second"));
+    assertTrue(result.contains("third"));
+  }
+
+  @Test
+  void shouldHandleDuplicateElements() {
+    HashSetBuilder<String> builder = new HashSetBuilder<>();
+    builder.add("duplicate").add("duplicate").add("unique");
+    Set<String> result = builder.build();
+
+    assertEquals(2, result.size());
+    assertTrue(result.contains("duplicate"));
+    assertTrue(result.contains("unique"));
+  }
+
+  @Test
+  void shouldAddAllFromSet() {
+    HashSetBuilder<Integer> builder = new HashSetBuilder<>();
+    builder.addAll(new HashSet<>(Arrays.asList(1, 2, 3)));
+    Set<Integer> result = builder.build();
+
+    assertEquals(3, result.size());
+    assertTrue(result.contains(1));
+    assertTrue(result.contains(2));
+    assertTrue(result.contains(3));
+  }
+
+  @Test
+  void shouldChainAddAndAddAll() {
+    HashSetBuilder<String> builder = new HashSetBuilder<>();
+    builder.add("first").addAll(new HashSet<>(Arrays.asList("second", "third"))).add("fourth");
+    Set<String> result = builder.build();
+
+    assertEquals(4, result.size());
+    assertTrue(result.contains("first"));
+    assertTrue(result.contains("second"));
+    assertTrue(result.contains("third"));
+    assertTrue(result.contains("fourth"));
+  }
+
+  @Test
+  void shouldReturnThisForFluentInterface() {
+    HashSetBuilder<String> builder = new HashSetBuilder<>();
+    HashSetBuilder<String> result = builder.add("test");
+
+    assertEquals(builder, result);
+  }
+}
diff --git a/core/src/test/java/org/javahelpers/simple/builders/core/util/TrackedValueTest.java b/core/src/test/java/org/javahelpers/simple/builders/core/util/TrackedValueTest.java
new file mode 100644
index 00000000..46aab1cf
--- /dev/null
+++ b/core/src/test/java/org/javahelpers/simple/builders/core/util/TrackedValueTest.java
@@ -0,0 +1,210 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2025 Andreas Igel
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.javahelpers.simple.builders.core.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+import org.junit.jupiter.api.Test;
+
+class TrackedValueTest {
+
+  @Test
+  void shouldCreateUnsetValue() {
+    TrackedValue<String> tracked = TrackedValue.unsetValue();
+
+    assertNull(tracked.value());
+    assertFalse(tracked.isChanged());
+    assertFalse(tracked.isInitial());
+    assertFalse(tracked.isSet());
+  }
+
+  @Test
+  void shouldCreateInitialValue() {
+    TrackedValue<String> tracked = TrackedValue.initialValue("test");
+
+    assertEquals("test", tracked.value());
+    assertFalse(tracked.isChanged());
+    assertTrue(tracked.isInitial());
+    assertTrue(tracked.isSet());
+  }
+
+  @Test
+  void shouldCreateInitialValueWithNull() {
+    TrackedValue<String> tracked = TrackedValue.initialValue(null);
+
+    assertNull(tracked.value());
+    assertFalse(tracked.isChanged());
+    assertTrue(tracked.isInitial());
+    assertTrue(tracked.isSet());
+  }
+
+  @Test
+  void shouldCreateChangedValue() {
+    TrackedValue<String> tracked = TrackedValue.changedValue("modified");
+
+    assertEquals("modified", tracked.value());
+    assertTrue(tracked.isChanged());
+    assertFalse(tracked.isInitial());
+    assertTrue(tracked.isSet());
+  }
+
+  @Test
+  void shouldCreateChangedValueWithNull() {
+    TrackedValue<String> tracked = TrackedValue.changedValue(null);
+
+    assertNull(tracked.value());
+    assertTrue(tracked.isChanged());
+    assertFalse(tracked.isInitial());
+    assertTrue(tracked.isSet());
+  }
+
+  @Test
+  void shouldReturnTrueForIsSetWhenChanged() {
+    TrackedValue<String> tracked = TrackedValue.changedValue("value");
+
+    assertTrue(tracked.isSet());
+  }
+
+  @Test
+  void shouldReturnTrueForIsSetWhenInitial() {
+    TrackedValue<String> tracked = TrackedValue.initialValue("value");
+
+    assertTrue(tracked.isSet());
+  }
+
+  @Test
+  void shouldReturnFalseForIsSetWhenUnset() {
+    TrackedValue<String> tracked = TrackedValue.unsetValue();
+
+    assertFalse(tracked.isSet());
+  }
+
+  @Test
+  void shouldExecuteConsumerWhenChanged() {
+    TrackedValue<String> tracked = TrackedValue.changedValue("test");
+    AtomicBoolean executed = new AtomicBoolean(false);
+    AtomicReference<String> capturedValue = new AtomicReference<>();
+
+    tracked.ifSet(
+        value -> {
+          executed.set(true);
+          capturedValue.set(value);
+        });
+
+    assertTrue(executed.get());
+    assertEquals("test", capturedValue.get());
+  }
+
+  @Test
+  void shouldExecuteConsumerWhenInitial() {
+    TrackedValue<String> tracked = TrackedValue.initialValue("initial");
+    AtomicBoolean executed = new AtomicBoolean(false);
+    AtomicReference<String> capturedValue = new AtomicReference<>();
+
+    tracked.ifSet(
+        value -> {
+          executed.set(true);
+          capturedValue.set(value);
+        });
+
+    assertTrue(executed.get());
+    assertEquals("initial", capturedValue.get());
+  }
+
+  @Test
+  void shouldNotExecuteConsumerWhenUnset() {
+    TrackedValue<String> tracked = TrackedValue.unsetValue();
+    AtomicBoolean executed = new AtomicBoolean(false);
+
+    tracked.ifSet(value -> executed.set(true));
+
+    assertFalse(executed.get());
+  }
+
+  @Test
+  void shouldPassNullToConsumerWhenValueIsNull() {
+    TrackedValue<String> tracked = TrackedValue.changedValue(null);
+    AtomicBoolean executed = new AtomicBoolean(false);
+    AtomicReference<String> capturedValue = new AtomicReference<>("not-null");
+
+    tracked.ifSet(
+        value -> {
+          executed.set(true);
+          capturedValue.set(value);
+        });
+
+    assertTrue(executed.get());
+    assertNull(capturedValue.get());
+  }
+
+  @Test
+  void shouldSupportRecordEquality() {
+    TrackedValue<String> tracked1 = new TrackedValue<>("test", true, false);
+    TrackedValue<String> tracked2 = new TrackedValue<>("test", true, false);
+
+    assertEquals(tracked1, tracked2);
+  }
+
+  @Test
+  void shouldSupportRecordHashCode() {
+    TrackedValue<String> tracked1 = new TrackedValue<>("test", true, false);
+    TrackedValue<String> tracked2 = new TrackedValue<>("test", true, false);
+
+    assertEquals(tracked1.hashCode(), tracked2.hashCode());
+  }
+
+  @Test
+  void shouldDistinguishDifferentStates() {
+    TrackedValue<String> unset = TrackedValue.unsetValue();
+    TrackedValue<String> initial = TrackedValue.initialValue("test");
+    TrackedValue<String> changed = TrackedValue.changedValue("test");
+
+    // Unset vs Initial
+    assertFalse(unset.isSet());
+    assertTrue(initial.isSet());
+
+    // Initial vs Changed
+    assertTrue(initial.isInitial());
+    assertFalse(changed.isInitial());
+    assertFalse(initial.isChanged());
+    assertTrue(changed.isChanged());
+  }
+
+  @Test
+  void shouldWorkWithComplexTypes() {
+    TrackedValue<Integer> intTracked = TrackedValue.changedValue(42);
+    TrackedValue<Double> doubleTracked = TrackedValue.initialValue(3.14);
+
+    assertEquals(42, intTracked.value());
+    assertEquals(3.14, doubleTracked.value());
+    assertTrue(intTracked.isSet());
+    assertTrue(doubleTracked.isSet());
+  }
+}

From 4d5bb0e6ce3f7cef922cdb00cd692d29a1292b81 Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:55:03 +0200
Subject: [PATCH 09/10] Adding test-setup

---
 core/pom.xml                | 2 +-
 core/src/test/java/.gitkeep | 0
 2 files changed, 1 insertion(+), 1 deletion(-)
 delete mode 100644 core/src/test/java/.gitkeep

diff --git a/core/pom.xml b/core/pom.xml
index a57bb7b9..538175c6 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -65,7 +65,7 @@
     <central.autoPublish>false</central.autoPublish>
     
     <!-- Dependency Versions -->
-    <junit-jupiter.version>6.0.0</junit-jupiter.version>
+    <junit-jupiter.version>5.11.4</junit-jupiter.version>
     
     <!-- Plugin Versions -->
     <plugin.central.publishing.version>0.9.0</plugin.central.publishing.version>
diff --git a/core/src/test/java/.gitkeep b/core/src/test/java/.gitkeep
deleted file mode 100644
index e69de29b..00000000

From 13fb306040c6b6d0e92413c97adb40c90cf6aabd Mon Sep 17 00:00:00 2001
From: AndreasIgel <AndreasIgel82@gmail.com>
Date: Sun, 19 Oct 2025 22:59:47 +0200
Subject: [PATCH 10/10] Adding jacoco configuration to core module to retrieve
 coverage

---
 core/pom.xml | 32 ++++++++++++++++++++++++++++++++
 pom.xml      |  2 +-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/core/pom.xml b/core/pom.xml
index 538175c6..c29417c8 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -76,6 +76,7 @@
     <plugin.maven.gpg.version>3.2.8</plugin.maven.gpg.version>
     <plugin.maven.install.version>3.1.4</plugin.maven.install.version>
     <plugin.maven.site.version>3.21.0</plugin.maven.site.version>
+    <plugin.jacoco.version>0.8.14</plugin.jacoco.version>
   </properties>
 
   <dependencies>
@@ -215,6 +216,37 @@
         </plugins>
       </build>
     </profile>
+    <profile>
+      <id>metrics</id>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.jacoco</groupId>
+            <artifactId>jacoco-maven-plugin</artifactId>
+            <version>${plugin.jacoco.version}</version>
+            <executions>
+              <execution>
+                <id>prepare-agent</id>
+                <goals>
+                  <goal>prepare-agent</goal>
+                </goals>
+              </execution>
+              <execution>
+                <id>report</id>
+                <phase>verify</phase>
+                <goals>
+                  <goal>report</goal>
+                </goals>
+              </execution>
+            </executions>
+            <configuration>
+              <dataFile>${project.build.directory}/jacoco.exec</dataFile>
+              <outputDirectory>${project.reporting.outputDirectory}/jacoco</outputDirectory>
+            </configuration>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
   </profiles>
 
 </project>
\ No newline at end of file
diff --git a/pom.xml b/pom.xml
index e1ba8ab2..09fa2537 100644
--- a/pom.xml
+++ b/pom.xml
@@ -73,7 +73,7 @@
     <sonar.projectName>Simple Builders</sonar.projectName>
     <sonar.host.url>https://sonarcloud.io</sonar.host.url>
     <sonar.java.binaries>${project.basedir}/core/target/classes,${project.basedir}/processor/target/classes</sonar.java.binaries>
-    <sonar.coverage.jacoco.xmlReportPaths>${project.basedir}/processor/target/site/jacoco/jacoco.xml</sonar.coverage.jacoco.xmlReportPaths>
+    <sonar.coverage.jacoco.xmlReportPaths>${project.basedir}/core/target/site/jacoco/jacoco.xml,${project.basedir}/processor/target/site/jacoco/jacoco.xml</sonar.coverage.jacoco.xmlReportPaths>
     <sonar.exclusions>**/example/**</sonar.exclusions>
     <!-- Coverage exclusion needs to match jacoco configuration in processor module -->
     <sonar.coverage.exclusions>**/*Mapper*.java,**/processor/dtos/**,**/generated/**</sonar.coverage.exclusions>