diff --git a/scan_asn1tag.c b/scan_asn1tag.c
index acf0c57..e124950 100644
--- a/scan_asn1tag.c
+++ b/scan_asn1tag.c
@@ -1,5 +1,11 @@
 #include "asn1.h"
 
+#ifdef UNITTEST
+#undef UNITTEST
+#include "scan_asn1tagint.c"
+#define UNITTEST
+#endif
+
 size_t scan_asn1tag(const char* src,const char* max,enum asn1_tagclass* tc,enum asn1_tagtype* tt,unsigned long* tag) {
   if (max<=src) return 0;
   *tc=(*src&0xC0);
@@ -15,3 +21,16 @@ size_t scan_asn1tag(const char* src,const char* max,enum asn1_tagclass* tc,enum
     return 1;
   }
 }
+
+#ifdef UNITTEST
+#include <assert.h>
+#include <string.h>
+
+int main() {
+  enum asn1_tagclass tc;
+  enum asn1_tagtype tt;
+  unsigned long tag;
+  char buf[10];
+  strcpy(buf,"\x01"); assert(scan_asn1tag(buf,buf+10,&tc,&tt,&tag)==1 && tc==UNIVERSAL && tt==PRIMITIVE && tag==BOOLEAN);
+}
+#endif
diff --git a/scan_asn1tagint.c b/scan_asn1tagint.c
index 2c23fa2..3085da0 100644
--- a/scan_asn1tagint.c
+++ b/scan_asn1tagint.c
@@ -13,3 +13,10 @@ size_t scan_asn1tagint(const char* src,const char* max,unsigned long* val) {
   *val=l;
   return src-orig+1;
 }
+
+#ifdef UNITTEST
+#include <assert.h>
+
+int main() {
+}
+#endif