diff --git a/processor/src/test/java/org/mapstruct/ap/testutil/assertions/JavaFileAssert.java b/processor/src/test/java/org/mapstruct/ap/testutil/assertions/JavaFileAssert.java
index 2f8b13ba25..277b552f72 100644
--- a/processor/src/test/java/org/mapstruct/ap/testutil/assertions/JavaFileAssert.java
+++ b/processor/src/test/java/org/mapstruct/ap/testutil/assertions/JavaFileAssert.java
@@ -10,6 +10,7 @@
 import java.io.UncheckedIOException;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -18,6 +19,7 @@
 import org.assertj.core.internal.Diff;
 import org.assertj.core.internal.Failures;
 import org.assertj.core.util.diff.Delta;
+import org.opentest4j.FileInfo;
 
 import static java.lang.String.format;
 
@@ -81,8 +83,22 @@ public void hasSameMapperContent(File expected) {
             ) );
             diffs.removeIf( this::ignoreDelta );
             if ( !diffs.isEmpty() ) {
+                FileInfo actualInfo;
+                FileInfo expectedInfo;
+                try {
+                    actualInfo = new FileInfo( actual.getAbsolutePath(), Files.readAllBytes( actual.toPath() ) );
+                    expectedInfo = new FileInfo( expected.getAbsolutePath(), Files.readAllBytes( expected.toPath() ) );
+                }
+                catch ( IOException e ) {
+                    throw new RuntimeException( e );
+                }
                 throw Failures.instance()
-                    .failure( info, ShouldHaveSameContent.shouldHaveSameContent( actual, expected, diffs ) );
+                    .failure(
+                        info,
+                        ShouldHaveSameContent.shouldHaveSameContent( actual, expected, diffs ),
+                        actualInfo,
+                        expectedInfo
+                    );
             }
         }
         catch ( IOException e ) {
diff --git a/processor/src/test/java/org/mapstruct/ap/testutil/runner/CompilingExtension.java b/processor/src/test/java/org/mapstruct/ap/testutil/runner/CompilingExtension.java
index 468e2908a1..eb18615b8b 100644
--- a/processor/src/test/java/org/mapstruct/ap/testutil/runner/CompilingExtension.java
+++ b/processor/src/test/java/org/mapstruct/ap/testutil/runner/CompilingExtension.java
@@ -674,7 +674,7 @@ boolean needsRecompilation(CompilationRequest compilationRequest, CompilationCac
         return !compilationRequest.equals( compilationCache.getLastRequest() );
     }
 
-    private static String getBasePath() {
+    static String getBasePath() {
         try {
             return new File( "." ).getCanonicalPath();
         }
diff --git a/processor/src/test/java/org/mapstruct/ap/testutil/runner/GeneratedSource.java b/processor/src/test/java/org/mapstruct/ap/testutil/runner/GeneratedSource.java
index 85b6ec80fd..7c6c447d77 100644
--- a/processor/src/test/java/org/mapstruct/ap/testutil/runner/GeneratedSource.java
+++ b/processor/src/test/java/org/mapstruct/ap/testutil/runner/GeneratedSource.java
@@ -6,9 +6,6 @@
 package org.mapstruct.ap.testutil.runner;
 
 import java.io.File;
-import java.net.URL;
-import java.net.URLDecoder;
-import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -19,6 +16,7 @@
 
 import static org.assertj.core.api.Assertions.fail;
 import static org.mapstruct.ap.testutil.runner.CompilingExtension.NAMESPACE;
+import static org.mapstruct.ap.testutil.runner.CompilingExtension.getBasePath;
 
 /**
  * A {@link org.junit.jupiter.api.extension.RegisterExtension RegisterExtension} to perform assertions on generated
@@ -36,6 +34,7 @@
 public class GeneratedSource implements BeforeTestExecutionCallback, AfterTestExecutionCallback {
 
     private static final String FIXTURES_ROOT = "fixtures/";
+    private static final String FIXTURES_DIR = getBasePath() + "/src/test/resources/fixtures/";
 
     /**
      * ThreadLocal, as the source dir must be injected for this extension to gain access
@@ -139,8 +138,8 @@ public JavaFileAssert forJavaFile(String path) {
     private void handleFixtureComparison() {
         for ( FixtureComparison fixture : fixturesFor ) {
             String fixtureName = getFixtureName( fixture.mapperClass, fixture.variant );
-            URL expectedFile = getExpectedResource( fixtureName );
-            if ( expectedFile == null ) {
+            File expectedFile = getExpectedResource( fixtureName );
+            if ( !expectedFile.exists() ) {
                 fail( String.format(
                     "No reference file could be found for Mapper %s. You should create a file %s",
                     fixture.mapperClass.getName(),
@@ -148,8 +147,7 @@ private void handleFixtureComparison() {
                 ) );
             }
             else {
-                File expectedResource = new File( URLDecoder.decode( expectedFile.getFile(), StandardCharsets.UTF_8 ) );
-                forMapper( fixture.mapperClass ).hasSameMapperContent( expectedResource );
+                forMapper( fixture.mapperClass ).hasSameMapperContent( expectedFile );
             }
         }
     }
@@ -159,16 +157,15 @@ private String getFixtureName(Class<?> mapperClass, String variant) {
         return mapperClass.getName().replace( '.', '/' ).concat( suffix );
     }
 
-    private URL getExpectedResource(String fixtureName) {
-        ClassLoader classLoader = getClass().getClassLoader();
+    private File getExpectedResource(String fixtureName) {
         for ( int version = Runtime.version().feature(); version >= 11 && compiler != Compiler.ECLIPSE; version-- ) {
-            URL resource = classLoader.getResource( FIXTURES_ROOT + "/" + version + "/" + fixtureName );
-            if ( resource != null ) {
-                return resource;
+            File fixtureFile = new File( FIXTURES_DIR + version + File.separator + fixtureName );
+            if ( fixtureFile.exists() ) {
+                return fixtureFile;
             }
         }
 
-        return classLoader.getResource( FIXTURES_ROOT + fixtureName );
+        return new File( FIXTURES_DIR + fixtureName );
     }
 
     private static final class FixtureComparison {