Extend the API to list files and directories

.gitignore

@@ -1,2 +1,3 @@
 .flattened-pom.xml
 target
+.idea

pom.xml

@@ -9,7 +9,7 @@
     </parent>
 
     <artifactId>fake-sftp-server-lambda</artifactId>
-    <version>2.0.0</version>
+    <version>2.1.0-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>Fake SFTP Server Lambda</name>

src/main/java/com/github/stefanbirkner/fakesftpserver/lambda/FakeSftpServer.java

@@ -16,6 +16,7 @@
 import java.nio.file.attribute.UserPrincipalLookupService;
 import java.nio.file.spi.FileSystemProvider;
 import java.util.*;
+import java.util.stream.Stream;
 
 import static com.github.marschall.memoryfilesystem.MemoryFileSystemBuilder.newLinux;
 import static java.nio.file.FileVisitResult.CONTINUE;
@@ -413,6 +414,21 @@ public boolean existsFile(
         return exists(pathAsObject) && !isDirectory(pathAsObject);
     }
 
+    /**
+     * List all files and directories in a given directory
+     * @param path the path to the directory
+     * @return a stream with of all files in the directory
+     * @throws IOException see {@link Files#list(Path)}
+     */
+    public Stream<Path> listFilesAndDirectories(
+        String path
+    ) throws IOException
+    {
+        verifyWithSftpServerIsNotFinished("list files");
+        Path pathAsObject = fileSystem.getPath(path);
+        return Files.list(pathAsObject);
+    }
+
     /**
      * Deletes all files and directories.
      * @throws IOException if an I/O error is thrown while deleting the files

src/test/java/com/github/stefanbirkner/fakesftpserver/lambda/FakeSftpServerTest.java

@@ -11,11 +11,15 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.ConnectException;
+import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.List;
 import java.util.Vector;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static com.github.stefanbirkner.fakesftpserver.lambda.FakeSftpServer.withSftpServer;
 import static com.github.stefanbirkner.fishbowl.Fishbowl.exceptionThrownBy;
@@ -603,6 +607,70 @@ public void existence_of_a_file_cannot_be_checked_outside_of_the_lambda(
         }
     }
 
+    public static class list_files_and_directories_check {
+        @Test
+        public void list_returns_all_existing_files_in_given_directory(
+        ) throws Exception {
+            withSftpServer(
+                server -> {
+                    uploadFile(
+                        server,
+                        "/dummy_directory/dummy_file.bin",
+                        DUMMY_CONTENT
+                    );
+                    uploadFile(
+                        server,
+                        "/dummy_directory/directory/dummy_file.bin",
+                        DUMMY_CONTENT
+                    );
+                    Stream<Path> fileList = server.listFilesAndDirectories(
+                        "/dummy_directory"
+                    );
+                    assertThat(fileList)
+                        .hasSize(2)
+                        .extracting(Path::toString)
+                        .contains("/dummy_directory/dummy_file.bin", "/dummy_directory/directory");
+                }
+            );
+        }
+
+        @Test
+        public void list_on_not_existing_directory_will_fail_with_exception(
+        ) throws Exception {
+            withSftpServer(
+                server -> {
+                    uploadFile(
+                        server,
+                        "/dummy_directory/dummy_file.bin",
+                        DUMMY_CONTENT
+                    );
+                    assertThatThrownBy(() -> server.listFilesAndDirectories(
+                        "/unknown_directory"
+                    )).isInstanceOf(NoSuchFileException.class);
+                }
+            );
+        }
+
+        @Test
+        public void list_cannot_be_checked_outside_of_the_lambda(
+        ) throws Exception {
+            AtomicReference<FakeSftpServer> serverCapture
+                = new AtomicReference<>();
+            withSftpServer(
+                serverCapture::set
+            );
+            Throwable exception = exceptionThrownBy(
+                () -> serverCapture.get().listFilesAndDirectories("/dummy_directory")
+            );
+            assertThat(exception)
+                .isInstanceOf(IllegalStateException.class)
+                .hasMessage(
+                    "Failed to list files because withSftpServer"
+                        + " is already finished."
+                );
+        }
+    }
+
     public static class server_shutdown {
         @Test
         public void after_a_successful_test_SFTP_server_is_shutdown(