diff --git a/tests/tests-skeletons/check-bits.c b/tests/tests-skeletons/check-bits.c
new file mode 100644
index 0000000..950a3e8
--- /dev/null
+++ b/tests/tests-skeletons/check-bits.c
@@ -0,0 +1,386 @@
+#include <stdio.h>
+#include <assert.h>
+
+#include <asn_bit_data.c>
+
+static void
+check_asn_bits_decoding() {
+	uint8_t buf[] = { 0xB7, 0x19, 0x2F, 0xEE, 0xAD };
+	uint8_t tmpbuf[10];
+	int32_t z;
+	asn_bit_data_t pos;
+	memset(&pos, 0, sizeof(pos));
+
+	pos.buffer = buf;
+	pos.nboff = 0;
+	pos.nbits = sizeof(buf) * 8;
+
+	z = asn_get_few_bits(&pos, 32);
+	assert(z == -1);
+	assert(pos.nbits == sizeof(buf) * 8);
+
+	z = asn_get_few_bits(&pos, 0);
+	assert(z == 0);
+	assert(pos.nboff == 0);
+	assert(pos.nbits == sizeof(buf) * 8);
+
+	z = asn_get_few_bits(&pos, 1);
+	assert(z == 1);
+	assert(pos.nboff == 1);
+	assert(pos.nbits == sizeof(buf) * 8);
+
+	z = asn_get_few_bits(&pos, 2);
+	assert(z == 1);
+	assert(pos.nboff == 3);
+	assert(pos.nbits == sizeof(buf) * 8);
+
+	z = asn_get_few_bits(&pos, 2);
+	assert(z == 2);
+	assert(pos.nboff == 5);
+	assert(pos.nbits == sizeof(buf) * 8);
+
+	z = asn_get_few_bits(&pos, 3);
+	assert(z == 7);
+	assert(pos.nboff == 8);
+	assert(pos.nbits == sizeof(buf) * 8);
+
+	z = asn_get_few_bits(&pos, 8);
+	assert(z == 0x19);
+	assert(pos.nboff == 8);
+	assert(pos.nbits == (sizeof(buf) - 1) * 8);
+
+	z = asn_get_few_bits(&pos, 1);
+	assert(z == 0);
+	assert(pos.nboff == 1);
+	assert(pos.nbits == (sizeof(buf) - 2) * 8);
+
+	z = asn_get_few_bits(&pos, 3);
+	assert(z == 2);
+	assert(pos.nboff == 4);
+	assert(pos.nbits == (sizeof(buf) - 2) * 8);
+
+	z = asn_get_few_bits(&pos, 8);
+	assert(z == 254);
+	assert(pos.nboff == 12);
+
+	pos.buffer = buf;
+	pos.nboff = 2;
+	pos.nbits = sizeof(buf) * 8;
+	z = asn_get_few_bits(&pos, 24);
+	assert(z == 14443711);
+
+	pos.buffer = (unsigned char *)"\001";
+	pos.nboff = 7;
+	pos.nbits = 7;
+	z = asn_get_few_bits(&pos, 1);
+	assert(pos.nboff == 7);
+	assert(pos.nbits == 7);
+	assert(z == -1);
+
+	pos.buffer = (unsigned char *)"\001";
+	pos.nboff = 7;
+	pos.nbits = 8;
+	z = asn_get_few_bits(&pos, 1);
+	assert(pos.nboff == 8);
+	assert(pos.nbits == 8);
+	assert(z == 1);
+
+	pos.buffer = (unsigned char *)"\000";
+	pos.nboff = 7;
+	pos.nbits = 8;
+	z = asn_get_few_bits(&pos, 1);
+	assert(pos.nboff == 8);
+	assert(pos.nbits == 8);
+	assert(z == 0);
+	z = asn_get_few_bits(&pos, 1);
+	assert(pos.nboff == 8);
+	assert(pos.nbits == 8);
+	assert(z == -1);
+
+	pos.buffer = (unsigned char *)"\000";
+	pos.nboff = 7;
+	pos.nbits = 9;
+	z = asn_get_few_bits(&pos, 1);
+	assert(pos.nboff == 8);
+	assert(pos.nbits == 9);
+	assert(z == 0);
+	z = asn_get_few_bits(&pos, 1);
+	assert(pos.nboff == 1);
+	assert(pos.nbits == 1);
+	assert(z == 0);
+
+	pos.buffer = (unsigned char *)"\001";
+	pos.nboff = 7;
+	pos.nbits = 9;
+	z = asn_get_few_bits(&pos, 1);
+	assert(pos.nboff == 8);
+	assert(pos.nbits == 9);
+	assert(z == 1);
+	z = asn_get_few_bits(&pos, 1);
+	assert(pos.nboff == 1);
+	assert(pos.nbits == 1);
+	assert(z == 0);
+
+	/* Get full 31-bit range */
+	pos.buffer = buf;
+	pos.nboff = 7;
+	pos.nbits = sizeof(buf) * 8;
+	z = asn_get_few_bits(&pos, 31);
+	assert(z == 1179384747);
+
+	/* Get a bit shifted range */
+	pos.buffer = buf;
+	pos.nboff = 6;
+	pos.nbits = sizeof(buf) * 8;
+	z = asn_get_few_bits(&pos, 31);
+	assert(z == 1663434197);
+
+	pos.buffer = buf;
+	pos.nboff = 0;
+	pos.nbits = sizeof(buf) * 8;
+	z = asn_get_many_bits(&pos, tmpbuf, 0, sizeof(buf) * 8);
+	assert(z == 0);
+	assert(buf[0] == tmpbuf[0]);
+	assert(buf[1] == tmpbuf[1]);
+	assert(buf[2] == tmpbuf[2]);
+	assert(buf[3] == tmpbuf[3]);
+	assert(buf[4] == tmpbuf[4]);
+
+	pos.buffer = buf;
+	pos.nboff = 1;
+	pos.nbits = sizeof(buf) * 8;
+	z = asn_get_many_bits(&pos, tmpbuf, 0, sizeof(buf) * 8);
+	assert(z == -1);
+
+	pos.buffer = buf;
+	pos.nboff = 1;
+	pos.nbits = sizeof(buf) * 8;
+	z = asn_get_many_bits(&pos, tmpbuf, 0, sizeof(buf) * 8 - 1);
+	assert(z == 0);
+	assert(tmpbuf[0] == 110);
+	assert(tmpbuf[1] == 50);
+	assert(tmpbuf[2] == 95);
+	assert(tmpbuf[3] == 221);
+	assert(tmpbuf[4] == 90);
+
+	pos.buffer = buf;
+	pos.nboff = 1;
+	pos.nbits = sizeof(buf) * 8;
+	z = asn_get_many_bits(&pos, tmpbuf, 1, sizeof(buf) * 8 - 1);
+	assert(z == 0);
+	assert(tmpbuf[0] == 55);
+	assert(tmpbuf[0] != buf[0]);
+	assert(tmpbuf[1] == buf[1]);
+	assert(tmpbuf[2] == buf[2]);
+	assert(tmpbuf[3] == buf[3]);
+	assert(tmpbuf[4] == buf[4]);
+}
+
+static int Ignore(const void *data, size_t size, void *op_key) {
+    (void)data;
+    (void)size;
+    (void)op_key;
+	return 0;
+}
+
+static void
+check_asn_bits_encoding() {
+	asn_bit_outp_t po;
+	int ret;
+
+	po.buffer = po.tmpspace;
+	po.nboff = 0;
+	po.nbits = 0;
+	po.output = Ignore;
+	po.op_key = 0;
+	po.tmpspace[0] = 0xff;
+
+	ret = asn_put_few_bits(&po, 0, 0);
+	assert(ret == 0);
+	assert(po.nboff == 0);
+	assert(po.buffer == po.tmpspace);
+	assert(po.tmpspace[0] == 0xff);
+
+	ret = asn_put_few_bits(&po, 0, 1);
+	assert(ret == 0);
+	assert(po.nboff == 1);
+	assert(po.nbits == 8 * sizeof(po.tmpspace));
+	assert(po.buffer == po.tmpspace);
+	assert(po.tmpspace[0] == 0x00);
+
+	ret = asn_put_few_bits(&po, 1, 1);
+	assert(ret == 0);
+	assert(po.nboff == 2);
+	assert(po.nbits == 8 * sizeof(po.tmpspace));
+	assert(po.buffer == po.tmpspace);
+	assert(po.tmpspace[0] == 0x40);
+
+	ret = asn_put_few_bits(&po, 1, 1);
+	assert(ret == 0);
+	assert(po.nboff == 3);
+	assert(po.nbits == 8 * sizeof(po.tmpspace));
+	assert(po.buffer == po.tmpspace);
+	assert(po.tmpspace[0] == 0x60);
+
+	ret = asn_put_few_bits(&po, 15, 5);
+	assert(ret == 0);
+	assert(po.nboff == 8);
+	assert(po.nbits == 8 * sizeof(po.tmpspace));
+	assert(po.buffer == po.tmpspace);
+	assert(po.tmpspace[0] == 0x6F);
+
+	ret = asn_put_few_bits(&po, 0xf0ff, 16);
+	assert(ret == 0);
+	assert(po.nboff == 16);
+	assert(po.nbits == 8 * sizeof(po.tmpspace) - 8);
+	assert(po.buffer == po.tmpspace + 1);
+	assert(po.tmpspace[0] == 0x6F);
+	assert(po.tmpspace[1] == 0xf0);
+	assert(po.tmpspace[2] == 0xff);
+
+	po.nboff--;
+
+	ret = asn_put_few_bits(&po, 2, 1);
+	assert(ret == 0);
+	assert(po.nboff == 8);
+	assert(po.nbits == 8 * sizeof(po.tmpspace) - 16);
+	assert(po.buffer == po.tmpspace + 2);
+	assert(po.tmpspace[0] == 0x6F);
+	assert(po.tmpspace[1] == 0xf0);
+	assert(po.tmpspace[2] == 0xfe);
+
+	ret = asn_put_few_bits(&po, 2, 32);
+	assert(ret == -1);
+
+	ret = asn_put_few_bits(&po, 2, -1);
+	assert(ret == -1);
+
+	ret = asn_put_few_bits(&po, -1, 31);
+	assert(ret == 0);
+	assert(po.nboff == 31);
+	assert(po.nbits == 8 * sizeof(po.tmpspace) - 24);
+	assert(po.buffer == po.tmpspace + 3);
+	assert(po.tmpspace[0] == 0x6F);
+	assert(po.tmpspace[1] == 0xf0);
+	assert(po.tmpspace[2] == 0xfe);
+	assert(po.tmpspace[3] == 0xff);
+	assert(po.tmpspace[4] == 0xff);
+	assert(po.tmpspace[5] == 0xff);
+	assert(po.tmpspace[6] == 0xfe);
+
+}
+
+/*
+ * Add N bits after P bits. Should result in N+P bits added.
+ */
+static void
+check_asn_bits_encoding_auto() {
+    int prior, next;
+    int ret, i;
+
+    for(prior = 0; prior <= 31; prior++) {
+      for(next = 0; next <= 31; next++) {
+        asn_bit_outp_t po;
+        po.buffer = po.tmpspace;
+        po.nboff = 0;
+        po.nbits = 0;
+        po.output = Ignore;
+        po.op_key = 0;
+        po.tmpspace[0] = 0xff;
+
+        ret = asn_put_few_bits(&po, -1, prior);
+        assert(ret == 0);
+
+		ASN_DEBUG(" (out{nboff=%d,nbits=%d,buf_offset=%d})", (int)po.nboff, (int)po.nbits, (int)(po.buffer - po.tmpspace));
+
+        ret = asn_put_few_bits(&po, -1, next);
+        assert(ret == 0);
+
+		ASN_DEBUG(" (out{nboff=%d,nbits=%d,buf_offset=%d})", (int)po.nboff, (int)po.nbits, (int)(po.buffer - po.tmpspace));
+
+		ASN_DEBUG("Putting %d + %d bits (%d/%d), got %d bytes and %d bits",
+            prior, next, (prior + next) / 8, (prior + next) % 8,
+            (int)(po.buffer - po.tmpspace), (int)po.nboff);
+        assert((po.buffer - po.tmpspace) * 8 + po.nboff == (size_t)(prior + next));
+        for(i = 0; i < (po.buffer - po.tmpspace); i++)
+            assert(po.tmpspace[0] == (unsigned char)-1);
+      }
+    }
+}
+
+static void
+check_asn_bits_sweep_with(uint8_t buf[], int already_bits, int add_bits) {
+	size_t buf_size = 8;
+	asn_bit_data_t pos;
+	asn_bit_outp_t out;
+	int32_t d_already;
+	int32_t d_add;
+	int32_t d_left;
+	int left_bits;
+
+	memset(&pos, 0, sizeof(pos));
+	pos.buffer = buf;
+	pos.nboff = 0;
+	pos.nbits = buf_size * 8;
+
+	memset(&out, 0, sizeof(out));
+	out.buffer = out.tmpspace;
+	out.nbits = 8 * sizeof(out.tmpspace);
+	assert(sizeof(out.tmpspace) >= buf_size);
+	memcpy(out.buffer, buf, buf_size);
+
+	d_already = asn_get_few_bits(&pos, already_bits);
+	d_add = asn_get_few_bits(&pos, add_bits);
+
+	asn_put_few_bits(&out, d_already, already_bits);
+	asn_put_few_bits(&out, d_add, add_bits);
+	if(out.nboff % 8) {
+		left_bits = 8 - (out.nboff % 8);
+		d_left = asn_get_few_bits(&pos, left_bits);
+	} else {
+		left_bits = 0;
+		d_left = 0;
+	}
+	asn_put_few_bits(&out, d_left, left_bits);
+	assert(0 == (out.nboff % 8));
+
+	if(0 != memcmp(out.tmpspace, buf, buf_size)) {
+		printf("IN: ");
+		for(size_t i = 0; i < buf_size; i++)
+			printf(" %02x", buf[i]);
+		printf("\nOUT:");
+		for(size_t i = 0; i < buf_size; i++)
+			printf(" %02x", out.tmpspace[i]);
+		printf(" (out{nboff=%d,left=%d,%02x})\n", (int)out.nboff, left_bits, (int)d_left);
+		assert(0 == memcmp(out.tmpspace, buf, buf_size));
+	}
+}
+
+static void
+check_asn_bits_sweep() {
+	uint8_t buf[3][8] = {
+		{ 0x55, 0xAA, 0x55, 0xAA, 0x55, 0xAA, 0x55, 0xAA },
+		{ 0xB7, 0x19, 0x2F, 0xEE, 0xAD, 0x11, 0xAA, 0x55 },
+		{ 0xEE, 0xAD, 0x11, 0xAA, 0x55, 0xB7, 0x19, 0x2F }
+	};
+	int already_bits;
+	int add_bits;
+	int buf_idx;
+
+	for(buf_idx = 0; buf_idx < 3; buf_idx++) {
+	 for(already_bits = 0; already_bits < 24; already_bits++) {
+	  for(add_bits = 0; add_bits <= 31; add_bits++) {
+	   check_asn_bits_sweep_with(buf[buf_idx], already_bits, add_bits);
+	  }
+	 }
+	}
+}
+
+int
+main() {
+	check_asn_bits_decoding();
+	check_asn_bits_encoding();
+	check_asn_bits_encoding_auto();
+	check_asn_bits_sweep();
+	return 0;
+}