diff --git a/core/src/test/java/io/github/muehmar/codegenerator/GeneratorTest.java b/core/src/test/java/io/github/muehmar/codegenerator/GeneratorTest.java
index 4738f3d..4b0f054 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/GeneratorTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/GeneratorTest.java
@@ -6,7 +6,7 @@
 import static io.github.muehmar.codegenerator.TestData.noData;
 import static io.github.muehmar.codegenerator.TestSettings.noSettings;
 import static io.github.muehmar.codegenerator.writer.Writer.javaWriter;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import ch.bluecare.commons.data.PList;
 import io.github.muehmar.codegenerator.TestData.BooleanData;
@@ -23,21 +23,21 @@ class GeneratorTest {
   void constant_when_created_then_correctOutput() {
     final Generator<Void, Void> gen = constant("Hello World!");
     final Writer writer = gen.generate(noData(), noSettings(), javaWriter());
-    assertEquals("Hello World!", writer.asString());
+    assertThat(writer.asString()).isEqualTo("Hello World!");
   }
 
   @Test
   void constant_when_formatArguments_then_correctOutput() {
     final Generator<Void, Void> gen = constant("Hello %s!", "World");
     final Writer writer = gen.generate(noData(), noSettings(), javaWriter());
-    assertEquals("Hello World!", writer.asString());
+    assertThat(writer.asString()).isEqualTo("Hello World!");
   }
 
   @Test
   void ofWriterFunction_when_created_then_correctOutput() {
     final Generator<Void, Void> gen = ofWriterFunction(w -> w.println("Hello World!"));
     final Writer writer = gen.generate(noData(), noSettings(), javaWriter());
-    assertEquals("Hello World!", writer.asString());
+    assertThat(writer.asString()).isEqualTo("Hello World!");
   }
 
   @Test
@@ -47,7 +47,7 @@ void appendGenerator_when_called_then_generatedCorrectAppended() {
 
     final Generator<Void, Void> gen = genA.append(genB);
     final Writer writer = gen.generate(noData(), noSettings(), javaWriter());
-    assertEquals("genA\ngenB", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\ngenB");
   }
 
   @Test
@@ -57,7 +57,7 @@ void appendGeneratorWithTabs_when_called_then_generatedCorrectAppendedWithIndent
 
     final Generator<Void, Void> gen = genA.append(genB, 2);
     final Writer writer = gen.generate(noData(), noSettings(), javaWriter());
-    assertEquals("genA\n    genB", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\n    genB");
   }
 
   @Test
@@ -66,7 +66,7 @@ void appendUnaryOperator_when_called_then_generatedCorrectAppend() {
 
     final Generator<Void, Void> gen = genA.append(w -> w.println("appended"));
     final Writer writer = gen.generate(noData(), noSettings(), javaWriter());
-    assertEquals("genA\nappended", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\nappended");
   }
 
   @Test
@@ -76,7 +76,7 @@ void appendMappingInput_when_called_then_generatedCorrectAppend() {
 
     final Generator<String, Void> gen = genA.append(genB, String::length);
     final Writer writer = gen.generate("Hello World!", noSettings(), javaWriter());
-    assertEquals("genA\n12", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\n12");
   }
 
   @Test
@@ -87,7 +87,7 @@ void appendMappingInputWithSettings_when_called_then_generatedCorrectAppend() {
     final Generator<String, Integer> gen =
         genA.append(genB, (in, settings) -> in.length() + settings);
     final Writer writer = gen.generate("Hello World!", 10, javaWriter());
-    assertEquals("genA\n22", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\n22");
   }
 
   @Test
@@ -102,7 +102,7 @@ void appendList_when_called_then_contentCreatedForEveryElementInTheList() {
         genA.appendList(fieldGen, ListData::getList);
     final Writer writer = generator.generate(data, noSettings(), javaWriter());
 
-    assertEquals("genA\nid\nusername\nnickname", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\nid\nusername\nnickname");
   }
 
   @Test
@@ -117,7 +117,7 @@ void appendList_when_calledWithSeparator_then_separatorAddedBetween() {
         genA.appendList(fieldGen, ListData::getList, ofWriterFunction(Writer::println));
     final Writer writer = generator.generate(data, noSettings(), javaWriter());
 
-    assertEquals("genA\nid\n\nusername\n\nnickname", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\nid\n\nusername\n\nnickname");
   }
 
   @Test
@@ -132,7 +132,7 @@ void appendList_when_emptyList_then_initialGenExecuted() {
         genA.appendList(fieldGen, ignore -> PList.empty(), ofWriterFunction(Writer::println));
     final Writer writer = generator.generate(data, noSettings(), javaWriter());
 
-    assertEquals("genA", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA");
   }
 
   @Test
@@ -144,7 +144,7 @@ void appendOptional_when_nonEmpty_then_contentAdded() {
         genA.appendOptional(genB, Function.identity());
     final Writer writer = generator.generate(Optional.of("data"), noSettings(), javaWriter());
 
-    assertEquals("genA\n-> data", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\n-> data");
   }
 
   @Test
@@ -156,7 +156,7 @@ void appendOptional_when_empty_then_nothingAdded() {
         genA.appendOptional(genB, Function.identity());
     final Writer writer = generator.generate(Optional.empty(), noSettings(), javaWriter());
 
-    assertEquals("genA", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA");
   }
 
   @Test
@@ -168,7 +168,7 @@ void appendConditionally_when_conditionEvaluatedToTrue_then_generatorAppended()
         genA.appendConditionally(genB, BooleanData::isFlag);
     final Writer writer = generator.generate(booleanData(true), noSettings(), javaWriter());
 
-    assertEquals("genA\ngenB", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\ngenB");
   }
 
   @Test
@@ -180,7 +180,7 @@ void appendConditionally_when_conditionEvaluatedToFalse_then_generatorNotAppende
         genA.appendConditionally(genB, BooleanData::isFlag);
     final Writer writer = generator.generate(booleanData(false), noSettings(), javaWriter());
 
-    assertEquals("genA", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA");
   }
 
   @Test
@@ -191,7 +191,7 @@ void filter_when_conditionIsTrue_then_generatorUnchanged() {
 
     final Writer writer = generator.generate(1, 2, javaWriter());
 
-    assertEquals("genA", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA");
   }
 
   @Test
@@ -202,7 +202,7 @@ void filter_when_conditionIsFalse_then_emptyGeneratorReturned() {
 
     final Writer writer = generator.generate(2, 2, javaWriter());
 
-    assertEquals("", writer.asString());
+    assertThat(writer.asString()).isEqualTo("");
   }
 
   @Test
@@ -214,7 +214,7 @@ void appendSingleBlankLine_when_called_then_outputHasNewLineAppended() {
             .appendSingleBlankLine()
             .generate(noData(), noSettings(), javaWriter());
 
-    assertEquals("genA\n", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\n");
   }
 
   @Test
@@ -223,7 +223,7 @@ void appendNewLine_when_called_then_outputHasNewLineAppended() {
 
     final Writer writer = genA.appendNewLine().generate(noData(), noSettings(), javaWriter());
 
-    assertEquals("genA\n", writer.asString());
+    assertThat(writer.asString()).isEqualTo("genA\n");
   }
 
   @Test
@@ -232,7 +232,7 @@ void prependNewLine_when_called_then_outputHasNewLinePrepended() {
 
     final Writer writer = genA.prependNewLine().generate(noData(), noSettings(), javaWriter());
 
-    assertEquals("\ngenA", writer.asString());
+    assertThat(writer.asString()).isEqualTo("\ngenA");
   }
 
   @Test
@@ -241,7 +241,7 @@ void int_when_called_then_indentedByGivenTabs() {
 
     final Writer writer = genA.indent(2).generate(noData(), noSettings(), javaWriter());
 
-    assertEquals("    genA", writer.asString());
+    assertThat(writer.asString()).isEqualTo("    genA");
   }
 
   @Test
@@ -252,6 +252,6 @@ void contraMap_when_newGenCalled_then_inputTransformedAccordingly() {
 
     final Writer writer = generator.generate(255, noSettings(), javaWriter());
 
-    assertEquals("ff", writer.asString());
+    assertThat(writer.asString()).isEqualTo("ff");
   }
 }
diff --git a/core/src/test/java/io/github/muehmar/codegenerator/java/ClassGenTest.java b/core/src/test/java/io/github/muehmar/codegenerator/java/ClassGenTest.java
index abe787c..57845f7 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/java/ClassGenTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/java/ClassGenTest.java
@@ -2,7 +2,7 @@
 
 import static io.github.muehmar.codegenerator.TestSettings.noSettings;
 import static io.github.muehmar.codegenerator.writer.Writer.javaWriter;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import ch.bluecare.commons.data.PList;
 import io.github.muehmar.codegenerator.Generator;
@@ -39,9 +39,13 @@ void generate_when_simplePojoAndSingleContent_then_correctGeneratedString() {
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals(
-        "package io.github.muehmar;\n" + "\n" + "public class HelloWorld {\n" + "  Content\n" + "}",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "package io.github.muehmar;\n"
+                + "\n"
+                + "public class HelloWorld {\n"
+                + "  Content\n"
+                + "}");
   }
 
   @Test
@@ -62,14 +66,14 @@ void generate_when_javaDoc_then_correctGeneratedString() {
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals(
-        "package io.github.muehmar;\n"
-            + "\n"
-            + "/** HelloWorld */\n"
-            + "public class HelloWorld {\n"
-            + "  Content\n"
-            + "}",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "package io.github.muehmar;\n"
+                + "\n"
+                + "/** HelloWorld */\n"
+                + "public class HelloWorld {\n"
+                + "  Content\n"
+                + "}");
   }
 
   @Test
@@ -90,13 +94,13 @@ void generate_when_interface_then_correctOutput() {
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals(
-        "package io.github.muehmar;\n"
-            + "\n"
-            + "public interface HelloWorld {\n"
-            + "  Content\n"
-            + "}",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "package io.github.muehmar;\n"
+                + "\n"
+                + "public interface HelloWorld {\n"
+                + "  Content\n"
+                + "}");
   }
 
   @Test
@@ -117,9 +121,13 @@ void generate_when_enum_then_correctOutput() {
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals(
-        "package io.github.muehmar;\n" + "\n" + "public enum HelloWorld {\n" + "  Content\n" + "}",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "package io.github.muehmar;\n"
+                + "\n"
+                + "public enum HelloWorld {\n"
+                + "  Content\n"
+                + "}");
   }
 
   @Test
@@ -140,13 +148,13 @@ void generate_when_interfaceInheritsInterface_then_correctInheritance() {
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals(
-        "package io.github.muehmar;\n"
-            + "\n"
-            + "public interface HelloWorld extends World {\n"
-            + "  Content\n"
-            + "}",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "package io.github.muehmar;\n"
+                + "\n"
+                + "public interface HelloWorld extends World {\n"
+                + "  Content\n"
+                + "}");
   }
 
   @Test
@@ -167,14 +175,14 @@ void generate_when_refAddedInContent_then_refPrinted() {
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals(
-        "package io.github.muehmar;\n"
-            + "\n"
-            + "import java.util.Optional;\n"
-            + "\n"
-            + "public class HelloWorld {\n"
-            + "}",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "package io.github.muehmar;\n"
+                + "\n"
+                + "import java.util.Optional;\n"
+                + "\n"
+                + "public class HelloWorld {\n"
+                + "}");
   }
 
   @Test
@@ -195,7 +203,7 @@ void generate_when_nestedClass_then_noRefsAndPackagePrinted() {
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals("public class HelloWorld {\n" + "}", writer.asString());
+    assertThat(writer.asString()).isEqualTo("public class HelloWorld {\n" + "}");
   }
 
   @ParameterizedTest
@@ -218,7 +226,7 @@ void generate_when_privateAndFinalModifierUnordered_then_correctOutputWithOrdere
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals("public final class HelloWorld {\n" + "}", writer.asString());
+    assertThat(writer.asString()).isEqualTo("public final class HelloWorld {\n" + "}");
   }
 
   @Test
@@ -239,7 +247,7 @@ void generate_when_hasSuperClass_then_correctOutput() {
 
     final Writer writer =
         generator.generate(new StringData("HelloWorld"), noSettings(), javaWriter());
-    assertEquals("public class HelloWorld extends Superclass {\n" + "}", writer.asString());
+    assertThat(writer.asString()).isEqualTo("public class HelloWorld extends Superclass {\n" + "}");
   }
 
   @Test
@@ -260,8 +268,8 @@ void generate_when_hasSuperClassAndInterfaces_then_correctOutput() {
 
     final Writer writer =
         generator.generate(TestData.stringListData("Hello", "World"), noSettings(), javaWriter());
-    assertEquals(
-        "public class Hello extends Superclass implements World {\n" + "}", writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo("public class Hello extends Superclass implements World {\n" + "}");
   }
 
   @Test
@@ -285,7 +293,8 @@ void generate_when_annotations_then_correctOutput() {
 
     final Writer writer =
         generator.generate(TestData.stringListData("Hello", "World"), noSettings(), javaWriter());
-    assertEquals("@Hello\n" + "@World\n" + "public class Hello {\n" + "}", writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo("@Hello\n" + "@World\n" + "public class Hello {\n" + "}");
   }
 
   private static Stream<Arguments> publicAndFinalModifierUnordered() {
diff --git a/core/src/test/java/io/github/muehmar/codegenerator/java/ConstructorGenTest.java b/core/src/test/java/io/github/muehmar/codegenerator/java/ConstructorGenTest.java
index 33c6701..1425aa2 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/java/ConstructorGenTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/java/ConstructorGenTest.java
@@ -1,7 +1,7 @@
 package io.github.muehmar.codegenerator.java;
 
 import static io.github.muehmar.codegenerator.writer.Writer.javaWriter;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import ch.bluecare.commons.data.PList;
 import lombok.Value;
@@ -26,9 +26,11 @@ void generate_when_minimalGeneratorCreated_then_outputCorrect() {
                 new ConstructorGen.Argument("int", "b")));
 
     final String output = generator.generate(data, null, javaWriter()).asString();
-    assertEquals(
-        "public Customer(String a, int b) {\n" + "  System.out.println(\"Hello World\");\n" + "}",
-        output);
+    assertThat(output)
+        .isEqualTo(
+            "public Customer(String a, int b) {\n"
+                + "  System.out.println(\"Hello World\");\n"
+                + "}");
   }
 
   @Value
diff --git a/core/src/test/java/io/github/muehmar/codegenerator/java/JavaDocGeneratorTest.java b/core/src/test/java/io/github/muehmar/codegenerator/java/JavaDocGeneratorTest.java
index 217444d..d17e8cb 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/java/JavaDocGeneratorTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/java/JavaDocGeneratorTest.java
@@ -2,7 +2,7 @@
 
 import static io.github.muehmar.codegenerator.TestSettings.noSettings;
 import static io.github.muehmar.codegenerator.writer.Writer.javaWriter;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import io.github.muehmar.codegenerator.Generator;
 import java.util.Arrays;
@@ -23,17 +23,17 @@ void javaDoc_when_javaDocWithLineBreaksButAlsoLongLines_then_keepLineBreaksAndAu
 
     final String output = generator.generate(input, noSettings(), javaWriter()).asString();
 
-    assertEquals(
-        "/**\n"
-            + " * This is some javadoc<br>\n"
-            + " *  1. Line one<br>\n"
-            + " *  2. Line two<br>\n"
-            + " *  3. This is a very long line! This is a very long line! This is a very long\n"
-            + " * line! This is a very long line! This is a very long line! This is a very long\n"
-            + " * line! This is a very long line! This is a very long line! This is a very long\n"
-            + " * line!\n"
-            + " */",
-        output);
+    assertThat(output)
+        .isEqualTo(
+            "/**\n"
+                + " * This is some javadoc<br>\n"
+                + " *  1. Line one<br>\n"
+                + " *  2. Line two<br>\n"
+                + " *  3. This is a very long line! This is a very long line! This is a very long\n"
+                + " * line! This is a very long line! This is a very long line! This is a very long\n"
+                + " * line! This is a very long line! This is a very long line! This is a very long\n"
+                + " * line!\n"
+                + " */");
   }
 
   @Test
@@ -44,13 +44,13 @@ void javaDoc_when_singleWordIsLongerThanMaxLength_then_longWordOnSingleLine() {
 
     final String output = generator.generate(input, noSettings(), javaWriter()).asString();
 
-    assertEquals(
-        "/**\n"
-            + " * Small Word\n"
-            + " * ThisIsAVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryLongWord\n"
-            + " * Small Word\n"
-            + " */",
-        output);
+    assertThat(output)
+        .isEqualTo(
+            "/**\n"
+                + " * Small Word\n"
+                + " * ThisIsAVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryVeryLongWord\n"
+                + " * Small Word\n"
+                + " */");
   }
 
   @Test
@@ -60,7 +60,7 @@ void javaDoc_when_singleShortLine_then_singleLineJavaDoc() {
 
     final String output = generator.generate(input, noSettings(), javaWriter()).asString();
 
-    assertEquals("/**\n" + " * Single Line Java Doc\n" + " */", output);
+    assertThat(output).isEqualTo("/**\n" + " * Single Line Java Doc\n" + " */");
   }
 
   @Test
@@ -69,15 +69,15 @@ void javaDoc_when_lineWith18CharactersAndEndsWithSpace_then_lastSpaceDiscarded()
     final String input =
         "This line contains 81 characters (maxlength+1) and the last character is a space ";
 
-    assertEquals(81, input.length());
+    assertThat(input.length()).isEqualTo(81);
 
     final String output = generator.generate(input, noSettings(), javaWriter()).asString();
 
-    assertEquals(
-        "/**\n"
-            + " * This line contains 81 characters (maxlength+1) and the last character is a space\n"
-            + " */",
-        output);
+    assertThat(output)
+        .isEqualTo(
+            "/**\n"
+                + " * This line contains 81 characters (maxlength+1) and the last character is a space\n"
+                + " */");
   }
 
   @Test
@@ -89,11 +89,11 @@ void javaDoc_when_singleLongWord_then_singleLineJavaDoc() {
 
     final String output = generator.generate(input, noSettings(), javaWriter()).asString();
 
-    assertEquals(
-        "/**\n"
-            + " * LooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongWord\n"
-            + " */",
-        output);
+    assertThat(output)
+        .isEqualTo(
+            "/**\n"
+                + " * LooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooongWord\n"
+                + " */");
   }
 
   @Test
@@ -108,13 +108,13 @@ void javaDoc_when_doubleLineBreak_then_keepLineBreaksAndAddBreakTag() {
                 javaWriter())
             .asString();
 
-    assertEquals(
-        "/**\n"
-            + " * This is a line followed by a double line break<br>\n"
-            + " * <br>\n"
-            + " * The line that follows\n"
-            + " */",
-        output);
+    assertThat(output)
+        .isEqualTo(
+            "/**\n"
+                + " * This is a line followed by a double line break<br>\n"
+                + " * <br>\n"
+                + " * The line that follows\n"
+                + " */");
   }
 
   @Test
@@ -123,6 +123,6 @@ void javaDoc_when_noJavaDocText_then_notOutput() {
 
     final String output = generator.generate("", noSettings(), javaWriter()).asString();
 
-    assertEquals("", output);
+    assertThat(output).isEqualTo("");
   }
 }
diff --git a/core/src/test/java/io/github/muehmar/codegenerator/java/JavaModifiersTest.java b/core/src/test/java/io/github/muehmar/codegenerator/java/JavaModifiersTest.java
index a49e6f5..91f15cc 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/java/JavaModifiersTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/java/JavaModifiersTest.java
@@ -1,6 +1,6 @@
 package io.github.muehmar.codegenerator.java;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import ch.bluecare.commons.data.PList;
 import java.util.stream.Stream;
@@ -16,7 +16,7 @@ class JavaModifiersTest {
   void
       asString_when_privateStaticFinalModifiersMultipleTimesAndDifferentOrder_then_singleOccurenceAndCorrectOrder(
           PList<JavaModifier> modifiers) {
-    assertEquals("private static final", JavaModifiers.of(modifiers).asString());
+    assertThat(JavaModifiers.of(modifiers).asString()).isEqualTo("private static final");
   }
 
   private static Stream<Arguments> privateStaticFinalModifiersMultipleTimesAndDifferentOrder() {
@@ -39,12 +39,12 @@ private static Stream<Arguments> privateStaticFinalModifiersMultipleTimesAndDiff
   @Test
   void asStringTrailingWhiteSpace_when_noModifiers_then_outputEmpty() {
     final JavaModifiers modifiers = JavaModifiers.of();
-    assertEquals("", modifiers.asStringTrailingWhitespace());
+    assertThat(modifiers.asStringTrailingWhitespace()).isEqualTo("");
   }
 
   @Test
   void asStringTrailingWhiteSpace_when_atLeastOneModifier_then_outputWithTrailingWhitespace() {
     final JavaModifiers modifiers = JavaModifiers.of(JavaModifier.PRIVATE);
-    assertEquals("private ", modifiers.asStringTrailingWhitespace());
+    assertThat(modifiers.asStringTrailingWhitespace()).isEqualTo("private ");
   }
 }
diff --git a/core/src/test/java/io/github/muehmar/codegenerator/java/MethodGenTest.java b/core/src/test/java/io/github/muehmar/codegenerator/java/MethodGenTest.java
index 846e6f6..844de9a 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/java/MethodGenTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/java/MethodGenTest.java
@@ -4,8 +4,7 @@
 import static io.github.muehmar.codegenerator.java.JavaModifier.FINAL;
 import static io.github.muehmar.codegenerator.java.JavaModifier.PUBLIC;
 import static io.github.muehmar.codegenerator.writer.Writer.javaWriter;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import ch.bluecare.commons.data.PList;
 import io.github.muehmar.codegenerator.writer.Writer;
@@ -33,11 +32,11 @@ void generate_when_minimalGeneratorCreated_then_outputCorrect() {
             PList.of(new MethodGen.Argument("String", "a"), new MethodGen.Argument("int", "b")));
 
     final String output = generator.generate(data, noSettings(), javaWriter()).asString();
-    assertEquals(
-        "public final void getXY(String a, int b) {\n"
-            + "  System.out.println(\"Hello World\");\n"
-            + "}",
-        output);
+    assertThat(output)
+        .isEqualTo(
+            "public final void getXY(String a, int b) {\n"
+                + "  System.out.println(\"Hello World\");\n"
+                + "}");
   }
 
   @Test
@@ -54,11 +53,11 @@ void generate_when_methodWithGenerics_then_outputCorrect() {
             .build();
 
     final String output = generator.generate("data", noSettings(), javaWriter()).asString();
-    assertEquals(
-        "public final <T, S> T doSomething(S s) throws IllegalStateException, IOException {\n"
-            + "  return s.getT();\n"
-            + "}",
-        output);
+    assertThat(output)
+        .isEqualTo(
+            "public final <T, S> T doSomething(S s) throws IllegalStateException, IOException {\n"
+                + "  return s.getT();\n"
+                + "}");
   }
 
   @Test
@@ -76,12 +75,12 @@ void generate_when_methodWithExceptionsGenerator_then_outputCorrect() {
             .build();
 
     final Writer writer = generator.generate("data", noSettings(), javaWriter());
-    assertEquals(
-        "public final <T, S> T doSomething(S s) throws CustomException {\n"
-            + "  return s.getT();\n"
-            + "}",
-        writer.asString());
-    assertEquals(PList.single("io.github.muehmar.CustomException"), writer.getRefs());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "public final <T, S> T doSomething(S s) throws CustomException {\n"
+                + "  return s.getT();\n"
+                + "}");
+    assertThat(writer.getRefs()).isEqualTo(PList.single("io.github.muehmar.CustomException"));
   }
 
   @Test
@@ -98,10 +97,9 @@ void generate_when_generatorForReturnType_then_outputAndRefsCorrect() {
             .build();
 
     final Writer writer = generator.generate("data", noSettings(), javaWriter());
-    assertEquals(
-        "public final returnSomething doSomething() {\n" + "  return xyz;\n" + "}",
-        writer.asString());
-    assertTrue(writer.getRefs().exists("somethingRef"::equals));
+    assertThat(writer.asString())
+        .isEqualTo("public final returnSomething doSomething() {\n" + "  return xyz;\n" + "}");
+    assertThat(writer.getRefs().exists("somethingRef"::equals)).isTrue();
   }
 
   @Value
diff --git a/core/src/test/java/io/github/muehmar/codegenerator/util/StringsTest.java b/core/src/test/java/io/github/muehmar/codegenerator/util/StringsTest.java
index 7acadc8..922ebbb 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/util/StringsTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/util/StringsTest.java
@@ -1,6 +1,6 @@
 package io.github.muehmar.codegenerator.util;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import org.junit.jupiter.api.Test;
 
@@ -9,12 +9,12 @@ class StringsTest {
   @Test
   void surroundIfNotEmpty_when_calledWithEmptyContent_then_returnsEmpty() {
     final String result = Strings.surroundIfNotEmpty("prefix", "", "suffix");
-    assertEquals("", result);
+    assertThat(result).isEqualTo("");
   }
 
   @Test
   void surroundIfNotEmpty_when_calledNonEmptyContent_then_contentPrefixedAndSuffixed() {
     final String result = Strings.surroundIfNotEmpty("prefix", "_content_", "suffix");
-    assertEquals("prefix_content_suffix", result);
+    assertThat(result).isEqualTo("prefix_content_suffix");
   }
 }
diff --git a/core/src/test/java/io/github/muehmar/codegenerator/writer/LineTest.java b/core/src/test/java/io/github/muehmar/codegenerator/writer/LineTest.java
index 9bf8d21..6dd94c4 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/writer/LineTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/writer/LineTest.java
@@ -1,6 +1,6 @@
 package io.github.muehmar.codegenerator.writer;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import ch.bluecare.commons.data.PList;
 import org.junit.jupiter.api.Test;
@@ -9,19 +9,19 @@ class LineTest {
   @Test
   void append_when_calledWithAdditionalFragment_then_fragmentAppended() {
     final Line helloWorld = Line.ofString("Hello").append(" World!");
-    assertEquals("Hello World!", helloWorld.asString());
+    assertThat(helloWorld.asString()).isEqualTo("Hello World!");
   }
 
   @Test
   void prepend_when_calledWithAdditionalFragment_then_fragmentPrepended() {
     final Line helloWorld = Line.ofString("World!").prepend("Hello ");
-    assertEquals("Hello World!", helloWorld.asString());
+    assertThat(helloWorld.asString()).isEqualTo("Hello World!");
   }
 
   @Test
   void prependList_when_calledWithAdditionalFragments_then_fragmentsPrepended() {
     final Line helloWorld = Line.ofString("World!").prepend(PList.of("Hello", " "));
-    assertEquals("Hello World!", helloWorld.asString());
+    assertThat(helloWorld.asString()).isEqualTo("Hello World!");
   }
 
   @Test
@@ -30,6 +30,6 @@ void prependList_when_calledWithAdditionalFragments_then_fragmentsPrepended() {
     final Line line =
         Line.ofString(" ").append("Hello").append(" ").append("World!").append("  ").append(" ");
 
-    assertEquals(" Hello World!", line.removeTrailingBlankFragments().asString());
+    assertThat(line.removeTrailingBlankFragments().asString()).isEqualTo(" Hello World!");
   }
 }
diff --git a/core/src/test/java/io/github/muehmar/codegenerator/writer/WriterTest.java b/core/src/test/java/io/github/muehmar/codegenerator/writer/WriterTest.java
index daa5a4b..c71f7e0 100644
--- a/core/src/test/java/io/github/muehmar/codegenerator/writer/WriterTest.java
+++ b/core/src/test/java/io/github/muehmar/codegenerator/writer/WriterTest.java
@@ -1,7 +1,7 @@
 package io.github.muehmar.codegenerator.writer;
 
 import static io.github.muehmar.codegenerator.writer.Writer.javaWriter;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import org.junit.jupiter.api.Test;
 
@@ -9,13 +9,13 @@ class WriterTest {
   @Test
   void print_when_formatStringWithArgs_then_formattedCorrectly() {
     final Writer writer = javaWriter().print("Format %s and %s!", "this", "that");
-    assertEquals("Format this and that!", writer.asString());
+    assertThat(writer.asString()).isEqualTo("Format this and that!");
   }
 
   @Test
   void tabAndPrint_when_tabAndFormatStringWithArgs_then_formattedCorrectly() {
     final Writer writer = javaWriter().tab(1).print("Format %s and %s!", "this", "that");
-    assertEquals("  Format this and that!", writer.asString());
+    assertThat(writer.asString()).isEqualTo("  Format this and that!");
   }
 
   @Test
@@ -26,19 +26,20 @@ void print_when_calledMultipleTimes_then_everythingOnOneLine() {
             .print(" And put")
             .print(" everything on the same")
             .print(" line.");
-    assertEquals("Format this and that! And put everything on the same line.", writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo("Format this and that! And put everything on the same line.");
   }
 
   @Test
   void println_when_calledTwoTimes_then_twoLinesCreated() {
     final Writer writer = javaWriter().println("Line number %d", 1).println("Line number %d", 2);
-    assertEquals("Line number 1\nLine number 2", writer.asString());
+    assertThat(writer.asString()).isEqualTo("Line number 1\nLine number 2");
   }
 
   @Test
   void tabAndPrintln_when_tabCalledBeforePrintLn_then_tabResettedAfterPrintLnCalled() {
     final Writer writer = javaWriter().tab(2).println("First line").println("Second line");
-    assertEquals("    First line\n" + "Second line", writer.asString());
+    assertThat(writer.asString()).isEqualTo("    First line\n" + "Second line");
   }
 
   @Test
@@ -52,14 +53,14 @@ void refAndPrintRefs_when_bothCalled_then_refsPrintedAndOrderedCorrectly() {
             .println("Third line")
             .ref("Ref C")
             .ref("Ref A");
-    assertEquals(
-        "First line\n"
-            + "import Ref A;\n"
-            + "import Ref B;\n"
-            + "import Ref C;\n"
-            + "Second line\n"
-            + "Third line",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "First line\n"
+                + "import Ref A;\n"
+                + "import Ref B;\n"
+                + "import Ref C;\n"
+                + "Second line\n"
+                + "Third line");
   }
 
   @Test
@@ -74,13 +75,13 @@ void append_when_calledForDifferentWriters_then_allLinesAppendedOnNewLines() {
             .print("Line after writer A")
             .append(writerB)
             .println("Line after writer B");
-    assertEquals(
-        "First line of main writer\n"
-            + "Something with a newline\n"
-            + "Line after writer A\n"
-            + "Something without a newline\n"
-            + "Line after writer B",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "First line of main writer\n"
+                + "Something with a newline\n"
+                + "Line after writer A\n"
+                + "Something without a newline\n"
+                + "Line after writer B");
   }
 
   @Test
@@ -92,8 +93,8 @@ void append_when_calledWithTabs_then_correctIndentionForAppendedContent() {
             .println("First line of main writer")
             .append(2, writerA)
             .println("Some other line");
-    assertEquals(
-        "First line of main writer\n" + "    Content writer A\nSome other line", writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo("First line of main writer\n" + "    Content writer A\nSome other line");
   }
 
   @Test
@@ -107,13 +108,13 @@ void append_when_writersPrintAndAddRefs_then_allRefsPrinted() {
             .append(writerA)
             .println("Line after writer A")
             .ref("Main writer ref");
-    assertEquals(
-        "First line of main writer\n"
-            + "import Main writer ref;\n"
-            + "import Writer A ref;\n"
-            + "Something of writer A\n"
-            + "Line after writer A",
-        writer.asString());
+    assertThat(writer.asString())
+        .isEqualTo(
+            "First line of main writer\n"
+                + "import Main writer ref;\n"
+                + "import Writer A ref;\n"
+                + "Something of writer A\n"
+                + "Line after writer A");
   }
 
   @Test
@@ -128,7 +129,7 @@ void asString_when_blankLineAppended_then_tabsRemovedOfBlankLine() {
             .println("Third line")
             .asString();
 
-    assertEquals("  First line\n" + "\n" + "  Third line", output);
+    assertThat(output).isEqualTo("  First line\n" + "\n" + "  Third line");
   }
 
   @Test
@@ -136,7 +137,7 @@ void asString_when_refsPrinted_then_javaLangImportsDropped() {
     final String output =
         javaWriter().printRefs().ref("java.lang.Integer").ref("java.util.Optional").asString();
 
-    assertEquals("import java.util.Optional;", output);
+    assertThat(output).isEqualTo("import java.util.Optional;");
   }
 
   @Test
@@ -148,7 +149,7 @@ void printSingleBlankLine_when_calledTwice_then_singleBlankLineAppended() {
             .printSingleBlankLine()
             .println("HELLO")
             .asString();
-    assertEquals("hello\n\nHELLO", output);
+    assertThat(output).isEqualTo("hello\n\nHELLO");
   }
 
   @Test
@@ -156,7 +157,7 @@ void asString_when_hasMultipleNewLinesAndNoMultipleNewLinesSettings_then_singleN
     final String output =
         javaWriter().println("Hello").println().println().println("World").asString();
 
-    assertEquals("Hello\n" + "\n" + "World", output);
+    assertThat(output).isEqualTo("Hello\n" + "\n" + "World");
   }
 
   @Test
@@ -169,7 +170,7 @@ void asString_when_hasMultipleNewLinesAndAllowMultipleNewLinesSettings_then_sing
             .println("World")
             .asString();
 
-    assertEquals("Hello\n" + "\n" + "\n" + "World", output);
+    assertThat(output).isEqualTo("Hello\n" + "\n" + "\n" + "World");
   }
 
   @Test
@@ -178,7 +179,7 @@ void asString_when_hasMultipleNewLinesAndAllowMultipleNewLinesSettings_then_sing
     final String output =
         javaWriter().println("Hello").println().printRefs().println().println("World").asString();
 
-    assertEquals("Hello\n" + "\n" + "World", output);
+    assertThat(output).isEqualTo("Hello\n" + "\n" + "World");
   }
 
   @Test
@@ -194,7 +195,7 @@ void asString_when_hasMultipleNewLinesAndAllowMultipleNewLinesSettings_then_sing
             .ref("ref-123")
             .asString();
 
-    assertEquals("Hello\n" + "\n" + "import ref-123;\n" + "\n" + "World", output);
+    assertThat(output).isEqualTo("Hello\n" + "\n" + "import ref-123;\n" + "\n" + "World");
   }
 
   @Test
@@ -209,6 +210,6 @@ void resetToLastNonEmptyLine_when_called_then_followingPrintStatementsAddToLastN
             .println("!")
             .asString();
 
-    assertEquals("Hello\n\nWorld!", output);
+    assertThat(output).isEqualTo("Hello\n\nWorld!");
   }
 }
diff --git a/settings.gradle b/settings.gradle
index 88c8c88..84d3d8e 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -9,7 +9,12 @@ dependencyResolutionManagement {
             library('junit-api', 'org.junit.jupiter', 'junit-jupiter-api').versionRef('junit')
             library('junit-engine', 'org.junit.jupiter', 'junit-jupiter-engine').versionRef('junit')
             library('junit-params', 'org.junit.jupiter', 'junit-jupiter-params').versionRef('junit')
-            bundle('junit', ['junit-api', 'junit-engine', 'junit-params'])
+
+            version('assertj', '3.26.3')
+            library('assertj', 'org.assertj', 'assertj-core').versionRef('assertj')
+
+
+            bundle('junit', ['junit-api', 'junit-engine', 'junit-params', 'assertj'])
 
             library('lombok', 'org.projectlombok:lombok:1.18.24')