Add initial empty unittest

tests/Makefile

@@ -1,9 +1,15 @@
 .PHONY: all clean
 
-all: basic
+all: basic unit_test
 
 basic: basic.c ../src/libtcap.so.0
 	gcc -Wall -g -I ../include -I../asn1-compiled basic.c -o basic -L../src -ltcap
 
+../src/libtcap.so.0:
+	cd .. && make all
+
+unit_test: unit_test.c
+	gcc -Wall -g unit_test.c -o unit_test -lcmocka
+
 clean:
-	rm -f basic
+	rm -f basic unit_test

tests/unit_test.c

@@ -0,0 +1,16 @@
+#include <stdarg.h>
+#include <stddef.h>
+#include <setjmp.h>
+#include <cmocka.h>
+
+/* A test case that does nothing and succeeds. */
+static void null_test_success(void **state) {
+    (void) state; /* unused */
+}
+
+int main(void) {
+    const UnitTest tests[] = {
+        unit_test(null_test_success),
+    };
+    return run_tests(tests);
+}