WIP. first step.

src/test/java/com/soebes/module/calculator/FileSelectorTest.java

@@ -37,6 +37,7 @@
 /**
  * @author Karl Heinz Marbaise
  */
+@MemoryFileSystem
 class FileSelectorTest {
 
   @Test

src/test/java/com/soebes/module/calculator/MemoryFileSystem.java

@@ -0,0 +1,18 @@
+package com.soebes.module.calculator;
+
+
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@ExtendWith(MemoryFileSystemExtension.class)
+@Documented
+public @interface MemoryFileSystem {
+}
+

src/test/java/com/soebes/module/calculator/FileSystemExtension.java → src/test/java/com/soebes/module/calculator/MemoryFileSystemExtension.java

@@ -7,7 +7,7 @@
 
 import java.nio.file.FileSystem;
 
-class FileSystemExtension implements BeforeEachCallback, AfterEachCallback {
+class MemoryFileSystemExtension implements BeforeEachCallback, AfterEachCallback {
 
   private FileSystem fileSystem;
 
@@ -17,7 +17,7 @@ FileSystem getFileSystem() {
 
   @Override
   public void beforeEach(ExtensionContext context) throws Exception {
-    this.fileSystem = MemoryFileSystemBuilder.newEmpty().build("name");
+    this.fileSystem = MemoryFileSystemBuilder.newEmpty().build();
   }
 
   @Override