diff --git a/modules/csvparser/tests/CMakeLists.txt b/modules/csvparser/tests/CMakeLists.txt
index 109fd35348..a6cc7d30bd 100644
--- a/modules/csvparser/tests/CMakeLists.txt
+++ b/modules/csvparser/tests/CMakeLists.txt
@@ -3,3 +3,4 @@ add_unit_test(LIBTEST CRITERION TARGET test_csvparser_from_config DEPENDS csvpar
 add_unit_test(CRITERION TARGET test_csvparser_perf DEPENDS csvparser)
 add_unit_test(CRITERION TARGET test_csvparser_statistics DEPENDS csvparser)
 add_unit_test(LIBTEST CRITERION TARGET test_filterx_func_parse_csv DEPENDS csvparser)
+add_unit_test(LIBTEST CRITERION TARGET test_filterx_func_format_csv DEPENDS csvparser)
diff --git a/modules/csvparser/tests/Makefile.am b/modules/csvparser/tests/Makefile.am
index cd91785d07..14c41537a1 100644
--- a/modules/csvparser/tests/Makefile.am
+++ b/modules/csvparser/tests/Makefile.am
@@ -2,7 +2,8 @@ modules_csvparser_tests_TESTS			=	\
 	modules/csvparser/tests/test_csvparser		\
 	modules/csvparser/tests/test_csvparser_from_config \
 	modules/csvparser/tests/test_csvparser_perf \
-	modules/csvparser/tests/test_filterx_func_parse_csv
+	modules/csvparser/tests/test_filterx_func_parse_csv \
+	modules/csvparser/tests/test_filterx_func_format_csv
 
 check_PROGRAMS					+=	\
 	${modules_csvparser_tests_TESTS}
@@ -44,3 +45,9 @@ modules_csvparser_tests_test_filterx_func_parse_csv_CFLAGS	=	\
 modules_csvparser_tests_test_filterx_func_parse_csv_LDADD	=	\
 	$(TEST_LDADD)					\
 	-dlpreopen $(top_builddir)/modules/csvparser/libcsvparser.la
+
+modules_csvparser_tests_test_filterx_func_format_csv_CFLAGS	=	\
+	$(TEST_CFLAGS) -I$(top_srcdir)/modules/csvparser
+modules_csvparser_tests_test_filterx_func_format_csv_LDADD	=	\
+	$(TEST_LDADD)					\
+	-dlpreopen $(top_builddir)/modules/csvparser/libcsvparser.la
diff --git a/modules/csvparser/tests/test_filterx_func_format_csv.c b/modules/csvparser/tests/test_filterx_func_format_csv.c
new file mode 100644
index 0000000000..e7490a19c9
--- /dev/null
+++ b/modules/csvparser/tests/test_filterx_func_format_csv.c
@@ -0,0 +1,221 @@
+/*
+ * Copyright (c) 2024 shifter
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As an additional exemption you are allowed to compile & link against the
+ * OpenSSL libraries as published by the OpenSSL project. See the file
+ * COPYING for details.
+ */
+
+#include <criterion/criterion.h>
+#include "libtest/filterx-lib.h"
+
+#include "filterx-func-format-csv.h"
+#include "filterx/expr-literal.h"
+#include "filterx/object-string.h"
+#include "filterx/object-primitive.h"
+#include "filterx/object-null.h"
+#include "filterx/object-json.h"
+
+#include "apphook.h"
+#include "scratch-buffers.h"
+
+static void
+_assert_format_csv_init_fail(GList *args)
+{
+  GError *err = NULL;
+  GError *args_err = NULL;
+  FilterXFunction *func = filterx_function_format_csv_new("test", filterx_function_args_new(args, &args_err), &err);
+  cr_assert(!func);
+  cr_assert(err);
+  g_error_free(err);
+}
+
+static void
+_assert_format_csv(GList *args, const gchar *expected_output)
+{
+  GError *err = NULL;
+  GError *args_err = NULL;
+  FilterXFunction *func = filterx_function_format_csv_new("test", filterx_function_args_new(args, &args_err), &err);
+  cr_assert(!err);
+
+  FilterXObject *obj = filterx_expr_eval(&func->super);
+  cr_assert(obj);
+
+  const gchar *output = filterx_string_get_value(obj, NULL);
+  cr_assert(output);
+
+  cr_assert_str_eq(output, expected_output);
+
+  filterx_object_unref(obj);
+  filterx_expr_unref(&func->super);
+}
+
+Test(filterx_func_format_csv, test_invalid_args)
+{
+  GList *args = NULL;
+
+  /* no args */
+  _assert_format_csv_init_fail(NULL);
+
+  /* empty args */
+  args = g_list_append(args, filterx_function_arg_new(NULL, NULL));
+  _assert_format_csv_init_fail(args);
+  args = NULL;
+
+  /* non literal delimiter */
+  args = g_list_append(args, filterx_function_arg_new(NULL, filterx_literal_new(filterx_test_dict_new())));
+  args = g_list_append(args, filterx_function_arg_new("delimiter", filterx_non_literal_new(filterx_string_new(",",
+                                                      -1))));
+  _assert_format_csv_init_fail(args);
+  args = NULL;
+
+  /* too long delimiter */
+  args = g_list_append(args, filterx_function_arg_new(NULL, filterx_literal_new(filterx_test_dict_new())));
+  args = g_list_append(args, filterx_function_arg_new("delimiter", filterx_literal_new(filterx_string_new(",!@#$",
+                                                      -1))));
+  _assert_format_csv_init_fail(args);
+  args = NULL;
+
+  /* too_many_args */
+  args = g_list_append(args, filterx_function_arg_new(NULL, filterx_literal_new(filterx_test_dict_new())));
+  args = g_list_append(args, filterx_function_arg_new(NULL, filterx_literal_new(filterx_string_new("=", -1))));
+  _assert_format_csv_init_fail(args);
+  args = NULL;
+}
+
+Test(filterx_func_format_csv, test_array_mode_with_default_delimiter)
+{
+  FilterXExpr *csv_data = filterx_literal_new(filterx_json_array_new_from_repr("[\"foo\", \"bar\", \"baz\"]", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+
+  _assert_format_csv(args, "foo bar baz");
+}
+
+Test(filterx_func_format_csv, test_array_mode_with_custom_delimiter)
+{
+  FilterXExpr *csv_data = filterx_literal_new(filterx_json_array_new_from_repr("[\"foo\", \"bar\", \"baz\"]", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+  args = g_list_append(args, filterx_function_arg_new(FILTERX_FUNC_FORMAT_CSV_ARG_NAME_DELIMITER,
+                                                      filterx_literal_new(filterx_string_new(";", -1))));
+
+  _assert_format_csv(args, "foo;bar;baz");
+}
+
+Test(filterx_func_format_csv, test_array_mode_skip_column_names)
+{
+  FilterXExpr *csv_data = filterx_literal_new(filterx_json_array_new_from_repr("[\"foo\", \"bar\", \"baz\"]", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+  args = g_list_append(args, filterx_function_arg_new(FILTERX_FUNC_FORMAT_CSV_ARG_NAME_COLUMNS,
+                                                      filterx_non_literal_new(filterx_json_array_new_from_repr("[\"col1\",\"col2\"]", -1))));
+
+  _assert_format_csv(args, "foo bar baz");
+}
+
+Test(filterx_func_format_csv, test_dict_mode_without_column_names_with_default_delimiter)
+{
+  FilterXExpr *csv_data = filterx_literal_new(
+                            filterx_json_object_new_from_repr("{\"col1\":\"foo\",\"col2\":\"bar\",\"col3\":\"baz\"}", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+
+  _assert_format_csv(args, "foo bar baz");
+}
+
+Test(filterx_func_format_csv, test_dict_mode_without_column_names_with_custom_delimiter)
+{
+  FilterXExpr *csv_data = filterx_literal_new(
+                            filterx_json_object_new_from_repr("{\"col1\":\"foo\",\"col2\":\"bar\",\"col3\":\"baz\"}", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+  args = g_list_append(args, filterx_function_arg_new(FILTERX_FUNC_FORMAT_CSV_ARG_NAME_DELIMITER,
+                                                      filterx_literal_new(filterx_string_new(";", -1))));
+
+  _assert_format_csv(args, "foo;bar;baz");
+}
+
+Test(filterx_func_format_csv, test_dict_mode_with_column_names_with_default_delimiter)
+{
+  FilterXExpr *csv_data = filterx_literal_new(
+                            filterx_json_object_new_from_repr("{\"col1\":\"foo\",\"col2\":\"bar\",\"col3\":\"baz\"}", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+  args = g_list_append(args, filterx_function_arg_new(FILTERX_FUNC_FORMAT_CSV_ARG_NAME_COLUMNS,
+                                                      filterx_non_literal_new(filterx_json_array_new_from_repr("[\"col2\",\"col1\"]", -1))));
+
+  _assert_format_csv(args, "bar foo");
+}
+
+Test(filterx_func_format_csv, test_dict_mode_with_column_names_with_custom_delimiter)
+{
+  FilterXExpr *csv_data = filterx_literal_new(
+                            filterx_json_object_new_from_repr("{\"col1\":\"foo\",\"col2\":\"bar\",\"col3\":\"baz\"}", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+  args = g_list_append(args, filterx_function_arg_new(FILTERX_FUNC_FORMAT_CSV_ARG_NAME_DELIMITER,
+                                                      filterx_literal_new(filterx_string_new(";", -1))));
+  args = g_list_append(args, filterx_function_arg_new(FILTERX_FUNC_FORMAT_CSV_ARG_NAME_COLUMNS,
+                                                      filterx_non_literal_new(filterx_json_array_new_from_repr("[\"col3\",\"col1\"]", -1))));
+
+  _assert_format_csv(args, "baz;foo");
+}
+
+Test(filterx_func_format_csv, test_add_double_quotes_when_delimiter_character_occours_in_data)
+{
+  FilterXExpr *csv_data = filterx_literal_new(
+                            filterx_json_object_new_from_repr("{\"col1\":\"fo;o\",\"col2\":\"b;ar\",\"col3\":\"baz\"}", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+  args = g_list_append(args, filterx_function_arg_new(FILTERX_FUNC_FORMAT_CSV_ARG_NAME_DELIMITER,
+                                                      filterx_literal_new(filterx_string_new(";", -1))));
+
+  // foo and bar gets double qouted since they contain delimiter character
+  _assert_format_csv(args, "\"fo;o\";\"b;ar\";baz");
+}
+
+Test(filterx_func_format_csv, test_escape_existing_double_quotes_in_case_of_adding_double_quotes)
+{
+  FilterXExpr *csv_data = filterx_literal_new(
+                            filterx_json_object_new_from_repr("{\"col1\":\"\\\"fo;o\\\"\",\"col2\":\"b;ar\",\"col3\":\"\\\"baz\\\"\"}", -1));
+  GList *args = NULL;
+  args = g_list_append(args, filterx_function_arg_new(NULL, csv_data));
+  args = g_list_append(args, filterx_function_arg_new(FILTERX_FUNC_FORMAT_CSV_ARG_NAME_DELIMITER,
+                                                      filterx_literal_new(filterx_string_new(";", -1))));
+
+  // foo's ("fo;o") double quotes need to be escaped, since it contains delimiter character and gets double quoted
+  // baz's ("baz") dobule quotes remain intact since won't be double quoted by the formatter
+  _assert_format_csv(args, "\"\\\"fo;o\\\"\";\"b;ar\";\"baz\"");
+}
+
+
+static void
+setup(void)
+{
+  app_startup();
+  init_libtest_filterx();
+}
+
+static void
+teardown(void)
+{
+  scratch_buffers_explicit_gc();
+  deinit_libtest_filterx();
+  app_shutdown();
+}
+
+TestSuite(filterx_func_format_csv, .init = setup, .fini = teardown);