diff --git a/CMakeLists.txt b/CMakeLists.txt
index c806aaa..44fd113 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,6 +2,7 @@ cmake_minimum_required(VERSION 3.13)
 project(gemhadar LANGUAGES C)
 
 add_subdirectory(lib)
+add_subdirectory(test)
 
 add_executable(gemhadar
     "main.c"
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
new file mode 100644
index 0000000..d720f59
--- /dev/null
+++ b/test/CMakeLists.txt
@@ -0,0 +1,6 @@
+add_library(test_lib
+    "test_io.c"
+)
+target_include_directories(test_lib PUBLIC "include")
+set_property(TARGET test_lib PROPERTY C_STANDARD 11)
+target_link_libraries(test_lib gemhadar_lib)
diff --git a/test/include/test_io.h b/test/include/test_io.h
new file mode 100644
index 0000000..dd11cbd
--- /dev/null
+++ b/test/include/test_io.h
@@ -0,0 +1,22 @@
+#ifndef TEST_IO_H
+#define TEST_IO_H
+
+#include "io_abs.h"
+
+struct test_reader_config {
+    const uint8_t *buf;
+    unsigned len;
+    unsigned pos;
+};
+
+void test_reader(struct test_reader_config *config, struct io_reader *reader_out);
+
+struct test_writer_config {
+    uint8_t *buf;
+    unsigned len;
+    unsigned pos;
+};
+
+void test_writer(struct test_writer_config *config, struct io_writer *writer_out);
+
+#endif
diff --git a/test/test_io.c b/test/test_io.c
new file mode 100644
index 0000000..f125254
--- /dev/null
+++ b/test/test_io.c
@@ -0,0 +1,35 @@
+#include "test_io.h"
+
+#include <string.h>
+
+static ssize_t test_reader_read(void *ctx, uint8_t *buf, size_t len)
+{
+    struct test_reader_config *config = (struct test_reader_config *)ctx;
+    const unsigned available = config->len - config->pos;
+    const unsigned to_read = len <= available ? len : available;
+    memcpy(buf, &config->buf[config->pos], to_read);
+    config->pos += to_read;
+    return to_read;
+}
+
+void test_reader(struct test_reader_config *config, struct io_reader *reader_out)
+{
+    reader_out->ctx = config;
+    reader_out->read = test_reader_read;
+}
+
+static ssize_t test_writer_write(void *ctx, const uint8_t *buf, size_t len)
+{
+    struct test_writer_config *config = (struct test_writer_config *)ctx;
+    const unsigned max = config->len - config->pos;
+    const unsigned to_write = len <= max ? len : max;
+    memcpy(&config->buf[config->pos], buf, to_write);
+    config->pos += to_write;
+    return to_write;
+}
+
+void test_writer(struct test_writer_config *config, struct io_writer *writer_out)
+{
+    writer_out->ctx = config;
+    writer_out->write = test_writer_write;
+}