Add tests for asn1_write_octet_string()
diff --git a/tests/suites/test_suite_asn1write.function b/tests/suites/test_suite_asn1write.function
new file mode 100644
index 0000000..53cb739
--- /dev/null
+++ b/tests/suites/test_suite_asn1write.function
@@ -0,0 +1,48 @@
+/* BEGIN_HEADER */
+#include <polarssl/asn1write.h>
+
+#define GUARD_LEN 4
+#define GUARD_VAL 0x2a
+/* END_HEADER */
+
+/* BEGIN_DEPENDENCIES
+ * depends_on:POLARSSL_ASN1_WRITE_C
+ * END_DEPENDENCIES
+ */
+
+/* BEGIN_CASE */
+void asn1_write_octet_string( char *hex_str, char *hex_asn1,
+                              int buf_len, int result )
+{
+    int ret;
+    unsigned char buf[150];
+    unsigned char str[150] = { 0 };
+    unsigned char asn1[150] = { 0 };
+    size_t str_len, asn1_len, i;
+    unsigned char *p;
+
+    memset( buf, GUARD_VAL, sizeof( buf ) );
+
+    str_len = unhexify( str, hex_str );
+    asn1_len = unhexify( asn1, hex_asn1 );
+
+    p = buf + GUARD_LEN + buf_len;
+
+    ret = asn1_write_octet_string( &p, buf + GUARD_LEN, str, str_len );
+
+    /* Check for buffer overwrite on both sides */
+    for( i = 0; i < GUARD_LEN; i++ )
+    {
+        TEST_ASSERT( buf[i] == GUARD_VAL );
+        TEST_ASSERT( buf[GUARD_LEN + buf_len + i] == GUARD_VAL );
+    }
+
+    if( result >= 0 )
+    {
+        TEST_ASSERT( (size_t) ret == asn1_len );
+        TEST_ASSERT( p + asn1_len == buf + GUARD_LEN + buf_len );
+
+        TEST_ASSERT( memcmp( p, asn1, asn1_len ) == 0 );
+    }
+}
+/* END_CASE */