diff --git a/src/test/java/de/kreth/property2java/ConfigurationTest.java b/src/test/java/de/kreth/property2java/ConfigurationTest.java
index c4f9e25..cdcafe3 100644
--- a/src/test/java/de/kreth/property2java/ConfigurationTest.java
+++ b/src/test/java/de/kreth/property2java/ConfigurationTest.java
@@ -16,18 +16,18 @@ import org.mockito.Mockito;
 
 class ConfigurationTest {
 
-	private Configuration config;
+	private TestImplConfig config;
 
 	@BeforeEach
 	void initConfig() {
-		config = Mockito.mock(Configuration.class);
+		config = Mockito.spy(TestImplConfig.class);
 	}
 
 	@Test
 	void defaultWriterIsFileWriter() throws IOException {
 
-		when(config.outWriter(anyString())).thenCallRealMethod();
 		when(config.getRootPath()).thenReturn(new File(".").toPath());
+		when(config.outWriter(anyString())).thenCallRealMethod();
 		when(config.mapFilenameToClassName(anyString())).thenCallRealMethod();
 		when(config.outputCharset()).thenCallRealMethod();
 
@@ -50,5 +50,4 @@ class ConfigurationTest {
 		className = config.mapFilenameToClassName("application_en_US.properties");
 		assertEquals("Application_Properties", className);
 	}
-
 }
diff --git a/src/test/java/de/kreth/property2java/GeneratorTests.java b/src/test/java/de/kreth/property2java/GeneratorTests.java
index 1229b38..ae925b1 100644
--- a/src/test/java/de/kreth/property2java/GeneratorTests.java
+++ b/src/test/java/de/kreth/property2java/GeneratorTests.java
@@ -10,6 +10,7 @@ import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.Reader;
 import java.io.StringReader;
@@ -26,6 +27,9 @@ import java.util.stream.Collectors;
 import org.hamcrest.Matchers;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+import de.kreth.property2java.processor.Format;
 
 class GeneratorTests {
 
@@ -40,7 +44,9 @@ class GeneratorTests {
 	Map<String, Reader> input = new HashMap<>();
 	input.put(path, testProperties());
 
-	config = mock(Configuration.class);
+	config = Mockito.spy(TestImplConfig.class);
+	when(config.getRootPath()).thenReturn(new File(".").toPath());
+	when(config.getFormat()).thenReturn(Format.WithInitializer);
 	when(config.getInput()).thenReturn(input);
 	when(config.mapFilenameToClassName(anyString())).thenCallRealMethod();
 	when(config.outputCharset()).thenCallRealMethod();
diff --git a/src/test/java/de/kreth/property2java/TestImplConfig.java b/src/test/java/de/kreth/property2java/TestImplConfig.java
new file mode 100644
index 0000000..6598dcd
--- /dev/null
+++ b/src/test/java/de/kreth/property2java/TestImplConfig.java
@@ -0,0 +1,27 @@
+package de.kreth.property2java;
+
+import java.io.Reader;
+import java.nio.file.Path;
+import java.util.Map;
+
+class TestImplConfig implements Configuration {
+
+	@Override
+	public String getPackage() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public Map<String, Reader> getInput() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+
+	@Override
+	public Path getRootPath() {
+		// TODO Auto-generated method stub
+		return null;
+	}
+	
+}
\ No newline at end of file