diff --git a/packaging/docker/Dockerfile.dev-centos b/packaging/docker/Dockerfile.dev-centos
index 1a54830da..898d002d2 100644
--- a/packaging/docker/Dockerfile.dev-centos
+++ b/packaging/docker/Dockerfile.dev-centos
@@ -28,7 +28,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ###################################################################################
 
-# This is a Centos 7 image including the devtoolset-7 for a more recenter toolchain
+# This is a Centos 7 image including the devtoolset-7 for a more up-to-date toolchain
 # See: https://www.softwarecollections.org/en/scls/rhscl/devtoolset-7/
 FROM registry.centos.org/centos/devtoolset-7-toolchain-centos7
 
@@ -108,12 +108,12 @@ RUN cd /tmp && \
 	rm -rf /tmp/spdlog
 
 # Build & Install Criterion
-RUN cd /tmp && \
-	git clone --recursive https://github.com/Snaipe/Criterion && \
-	mkdir -p Criterion/build && cd Criterion/build && \
-	git checkout v2.3.3 && \
-	cmake3 -DCMAKE_INSTALL_LIBDIR=/usr/local/lib64 .. && make install && \
-	rm -rf /tmp/*
+#RUN cd /tmp && \
+#	git clone --recursive https://github.com/Snaipe/Criterion && \
+#	mkdir -p Criterion/build && cd Criterion/build && \
+#	git checkout v2.3.3 && \
+#	cmake3 -DCMAKE_INSTALL_LIBDIR=/usr/local/lib64 .. && make install && \
+#	rm -rf /tmp/*
 
 # Build & Install libwebsockets
 RUN cd /tmp && \
diff --git a/tests/unit/CMakeLists.txt b/tests/unit/CMakeLists.txt
index 6ec8a8ae1..570963c8c 100644
--- a/tests/unit/CMakeLists.txt
+++ b/tests/unit/CMakeLists.txt
@@ -31,6 +31,7 @@ set(TEST_SRC
 	queue.cpp
 	queue_signalled.cpp
 	signal.cpp
+	helpers.cpp
 )
 
 add_executable(unit-tests ${TEST_SRC})
diff --git a/tests/unit/helpers.cpp b/tests/unit/helpers.cpp
new file mode 100644
index 000000000..23866e41c
--- /dev/null
+++ b/tests/unit/helpers.cpp
@@ -0,0 +1,13 @@
+#include <cstring>
+
+#include <criterion/criterion.h>
+
+#include "helpers.hpp"
+
+char * cr_strdup(const char *str)
+{
+	char *ptr = (char *) cr_malloc(strlen(str) + 1);
+	if (ptr)
+		strcpy(ptr, str);
+	return ptr;
+}
diff --git a/tests/unit/helpers.hpp b/tests/unit/helpers.hpp
new file mode 100644
index 000000000..61f8cc925
--- /dev/null
+++ b/tests/unit/helpers.hpp
@@ -0,0 +1,3 @@
+#pragma once
+
+char * cr_strdup(const char *str);
diff --git a/tests/unit/io.cpp b/tests/unit/io.cpp
index 81fefa31b..3df15b7ca 100644
--- a/tests/unit/io.cpp
+++ b/tests/unit/io.cpp
@@ -36,34 +36,40 @@
 #include <villas/io.h>
 #include <villas/log.hpp>
 
+#include "helpers.hpp"
+
 using namespace villas;
 
 extern void init_memory();
 
 #define NUM_VALUES 10
 
-struct param {
-	std::basic_string<char, std::char_traits<char>, criterion::allocator<char>> fmt;
+class Param {
+
+public:
+	char * fmt;
 	int cnt;
 	int bits;
 };
 
-static struct param params[] = {
-	{ "gtnet",		1, 32 },
-	{ "gtnet.fake",		1, 32 },
-	{ "raw.8",		1,  8 },
-	{ "raw.16.be",		1, 16 },
-	{ "raw.16.le",		1, 16 },
-	{ "raw.32.be",		1, 32 },
-	{ "raw.32.le",		1, 32 },
-	{ "raw.64.be",		1, 64 },
-	{ "raw.64.le",		1, 64 },
-	{ "villas.human",	10, 0 },
-	{ "villas.binary",	10, 0 },
-	{ "csv",		10, 0 },
-	{ "json",		10, 0 },
+const auto d = cr_strdup;
+
+static criterion::parameters<Param> params = {
+	{ d("gtnet"),		1, 32 },
+	{ d("gtnet.fake"),	1, 32 },
+	{ d("raw.8"),		1,  8 },
+	{ d("raw.16.be"),	1, 16 },
+	{ d("raw.16.le"),	1, 16 },
+	{ d("raw.32.be"),	1, 32 },
+	{ d("raw.32.le"),	1, 32 },
+	{ d("raw.64.be"),	1, 64 },
+	{ d("raw.64.le"),	1, 64 },
+	{ d("villas.human"),	10, 0 },
+	{ d("villas.binary"),	10, 0 },
+	{ d("csv"),		10, 0 },
+	{ d("json"),		10, 0 },
 #ifdef PROTOBUF_FOUND
-	{ "protobuf",		10, 0 }
+	{ d("protobuf"),	10, 0 }
 #endif
 };
 
@@ -205,10 +211,10 @@ void cr_assert_eq_sample_raw(struct sample *a, struct sample *b, int flags, int
 
 ParameterizedTestParameters(io, lowlevel)
 {
-	return criterion_test_params(params);
+	return params;
 }
 
-ParameterizedTest(struct param *p, io, lowlevel, .init = init_memory)
+ParameterizedTest(Param *p, io, lowlevel, .init = init_memory)
 {
 	int ret;
 	unsigned cnt;
@@ -241,8 +247,8 @@ ParameterizedTest(struct param *p, io, lowlevel, .init = init_memory)
 
 	fill_sample_data(&signals, smps, p->cnt);
 
-	f = format_type_lookup(p->fmt.c_str());
-	cr_assert_not_null(f, "Format '%s' does not exist", p->fmt.c_str());
+	f = format_type_lookup(p->fmt);
+	cr_assert_not_null(f, "Format '%s' does not exist", p->fmt);
 
 	ret = io_init(&io, f, &signals, (int) SampleFlags::HAS_ALL);
 	cr_assert_eq(ret, 0);
@@ -274,10 +280,10 @@ ParameterizedTest(struct param *p, io, lowlevel, .init = init_memory)
 
 ParameterizedTestParameters(io, highlevel)
 {
-	return criterion_test_params(params);
+	return params;
 }
 
-ParameterizedTest(struct param *p, io, highlevel, .init = init_memory)
+ParameterizedTest(Param *p, io, highlevel, .init = init_memory)
 {
 	int ret, cnt;
 	char *retp;
@@ -322,8 +328,8 @@ ParameterizedTest(struct param *p, io, highlevel, .init = init_memory)
 	ret = asprintf(&fn, "%s/file", dir);
 	cr_assert_gt(ret, 0);
 
-	f = format_type_lookup(p->fmt.c_str());
-	cr_assert_not_null(f, "Format '%s' does not exist", p->fmt.c_str());
+	f = format_type_lookup(p->fmt);
+	cr_assert_not_null(f, "Format '%s' does not exist", p->fmt);
 
 	ret = io_init(&io, f, &signals, (int) SampleFlags::HAS_ALL);
 	cr_assert_eq(ret, 0);
diff --git a/tests/unit/json.cpp b/tests/unit/json.cpp
index 9db7999ba..a47393cb1 100644
--- a/tests/unit/json.cpp
+++ b/tests/unit/json.cpp
@@ -27,54 +27,56 @@
 #include <villas/utils.hpp>
 #include <villas/config_helper.hpp>
 
-using str = std::basic_string<char, std::char_traits<char>, criterion::allocator<char>>;
+#include "helpers.hpp"
 
 struct param {
-	std::vector<str, criterion::allocator<str>> argv;
-	str json;
+	char *argv[32];
+	char *json;
 };
 
 ParameterizedTestParameters(json, json_load_cli)
 {
-	static struct param params[] = {
+	const auto d = cr_strdup;
+
+	static criterion::parameters<struct param> params = {
 		// Combined long option
 		{
-			.argv = { "dummy", "--option=value" },
-			.json = "{ \"option\" : \"value\" }"
+			.argv = { d("dummy"), d("--option=value") },
+			.json = d("{ \"option\" : \"value\" }")
 		},
 		// Separated long option
 		{
-			.argv = { "dummy", "--option", "value" },
-			.json = "{ \"option\" : \"value\" }"
+			.argv = { d("dummy"), d("--option"), d("value") },
+			.json = d("{ \"option\" : \"value\" }")
 		},
 		// All kinds of data types
 		{
-			.argv = { "dummy", "--integer", "1", "--real", "1.1", "--bool", "true", "--null", "null", "--string", "hello world" },
-			.json = "{ \"integer\" : 1, \"real\" : 1.1, \"bool\" : true, \"null\" : null, \"string\" : \"hello world\" }"
+			.argv = { d("dummy"), d("--integer"), d("1"), d("--real"), d("1.1"), d("--bool"), d("true"), d("--null"), d("null"), d("--string"), d("hello world") },
+			.json = d("{ \"integer\" : 1, \"real\" : 1.1, \"bool\" : true, \"null\" : null, \"string\" : \"hello world\" }")
 		},
 		// Array generation
 		{
-			.argv = { "dummy", "--bool", "true", "--bool", "false" },
-			.json = "{ \"bool\" : [ true, false ] }"
+			.argv = { d("dummy"), d("--bool"), d("true"), d("--bool"), d("false") },
+			.json = d("{ \"bool\" : [ true, false ] }")
 		},
 		// Dots in the option name generate sub objects
 		{
-			.argv = { "dummy", "--sub.option", "value" },
-			.json = "{ \"sub\" : { \"option\" : \"value\" } }"
+			.argv = { d("dummy"), d("--sub.option"), d("value") },
+			.json = d("{ \"sub\" : { \"option\" : \"value\" } }")
 		},
 		// Nesting is possible
 		{
-			.argv = { "dummy", "--sub.sub.option", "value" },
-			.json = "{ \"sub\" : { \"sub\" : { \"option\" : \"value\" } } }"
+			.argv = { d("dummy"), d("--sub.sub.option"), d("value") },
+			.json = d("{ \"sub\" : { \"sub\" : { \"option\" : \"value\" } } }")
 		},
 		// Multiple subgroups are merged
 		{
-			.argv = { "dummy", "--sub.sub.option", "value1", "--sub.option", "value2" },
-			.json = "{ \"sub\" : { \"option\" : \"value2\", \"sub\" : { \"option\" : \"value1\" } } }"
+			.argv = { d("dummy"), d("--sub.sub.option"), d("value1"), d("--sub.option"), d("value2") },
+			.json = d("{ \"sub\" : { \"option\" : \"value2\", \"sub\" : { \"option\" : \"value1\" } } }")
 		}
 	};
 
-	return criterion_test_params(params);
+	return params;
 }
 
 ParameterizedTest(struct param *p, json, json_load_cli)
@@ -82,15 +84,13 @@ ParameterizedTest(struct param *p, json, json_load_cli)
 	json_error_t err;
 	json_t *json, *cli;
 
-	json = json_loads(p->json.c_str(), 0, &err);
+	json = json_loads(p->json, 0, &err);
 	cr_assert_not_null(json);
 
-	auto argv = new const char*[p->argv.size() + 1];
-	for (unsigned i = 0; i < p->argv.size(); i++)
-		argv[i] = p->argv[i].c_str();
-	argv[p->argv.size()] = nullptr;
+	int argc = 0;
+	while (p->argv[argc]) argc++;
 
-	cli = json_load_cli(p->argv.size(), argv);
+	cli = json_load_cli(argc, (const char **) p->argv);
 	cr_assert_not_null(cli);
 
 	//json_dumpf(json, stdout, JSON_INDENT(2)); putc('\n', stdout);