diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d75752c..bc40eb1 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -40,6 +40,7 @@
 add_test_suite(aes aes.cfb)
 add_test_suite(aes aes.rest)
 add_test_suite(arc4)
+add_test_suite(asn1write)
 add_test_suite(base64)
 add_test_suite(blowfish)
 add_test_suite(camellia)
diff --git a/tests/Makefile b/tests/Makefile
index 61e38c4..dd9f205 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -32,7 +32,7 @@
 
 APPS =	test_suite_aes.ecb		test_suite_aes.cbc		\
 		test_suite_aes.cfb		test_suite_aes.rest		\
-		test_suite_arc4									\
+		test_suite_arc4			test_suite_asn1write	\
 		test_suite_base64		test_suite_blowfish		\
 		test_suite_camellia		test_suite_ccm			\
 		test_suite_cipher.aes							\
@@ -192,6 +192,10 @@
 	echo   "  CC    	$@.c"
 	$(CC) $(CFLAGS) $(OFLAGS) $@.c	$(LDFLAGS) -o $@
 
+test_suite_asn1write: test_suite_asn1write.c $(DEP)
+	echo   "  CC    	$@.c"
+	$(CC) $(CFLAGS) $(OFLAGS) $@.c	$(LDFLAGS) -o $@
+
 test_suite_base64: test_suite_base64.c $(DEP)
 	echo   "  CC    	$@.c"
 	$(CC) $(CFLAGS) $(OFLAGS) $@.c	$(LDFLAGS) -o $@
diff --git a/tests/suites/test_suite_asn1write.data b/tests/suites/test_suite_asn1write.data
new file mode 100644
index 0000000..c9b20d7
--- /dev/null
+++ b/tests/suites/test_suite_asn1write.data
@@ -0,0 +1,32 @@
+ASN.1 Write Octet String #0 (Empty string)
+asn1_write_octet_string:"":"0400":2:2
+
+ASN.1 Write Octet String #1 (Large buffer)
+asn1_write_octet_string:"AABBCC":"0403AABBCC":10:5
+
+ASN.1 Write Octet String #2 (Buffer just fits)
+asn1_write_octet_string:"AABBCC":"0403AABBCC":5:5
+
+ASN.1 Write Octet String #3 (Buffer too small for tag)
+asn1_write_octet_string:"AABBCC":"0403AABBCC":4:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
+
+ASN.1 Write Octet String #4 (Buffer too small for len)
+asn1_write_octet_string:"AABBCC":"0403AABBCC":3:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
+
+ASN.1 Write Octet String #5 (Buffer too small for string)
+asn1_write_octet_string:"AABBCC":"0403AABBCC":2:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
+
+ASN.1 Write Octet String #6 (l = 128, large buffer)
+asn1_write_octet_string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
+
+ASN.1 Write Octet String #7 (l = 128, buffer just fits)
+asn1_write_octet_string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
+
+ASN.1 Write Octet String #8 (l = 128, buffer too small for tag)
+asn1_write_octet_string:"000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F":"":130:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
+
+ASN.1 Write Octet String #9 (l = 128, buffer too small for len)
+asn1_write_octet_string:"000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F":"":129:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
+
+ASN.1 Write Octet String #9 (l = 128, buffer too small for string)
+asn1_write_octet_string:"000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F":"":127:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
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 */