diff --git a/tests/test_code_content_image.py b/tests/test_code_content_image.py
index dc6e2e3..85bf467 100644
--- a/tests/test_code_content_image.py
+++ b/tests/test_code_content_image.py
@@ -91,6 +91,11 @@ def test_gen_image_code_schema_conformance():
     assert iscc_obj.iscc == "ISCC:EEA4GQZQTY6J5DTH"
 
 
+def test_soft_hash_image_v0_larger_256_raises():
+    with pytest.raises(AssertionError):
+        ic.soft_hash_image_v0(IMG_SAMPLE_PIXELS, bits=288)
+
+
 IMG_WHITE_PIXELS = [255] * 1024
 IMG_BLACK_PIXELS = [0] * 1024
 IMG_SAMPLE_PIXELS = [
diff --git a/tests/test_iscc_id.py b/tests/test_iscc_id.py
index a19adf5..a1bc16e 100644
--- a/tests/test_iscc_id.py
+++ b/tests/test_iscc_id.py
@@ -1,5 +1,8 @@
 # -*- coding: utf-8 -*-
 import io
+
+import pytest
+
 import iscc_core as ic
 
 
@@ -62,3 +65,24 @@ def test_incr_iscc_id_v0():
     assert ic.iscc_id.incr_iscc_id_v0("MAADB7WD7TC5XELQ") == "MAADB7WD7TC5XELQAE"
     assert ic.Code("MAADB7WD7TC5XELQAE").explain == "ID-PRIVATE-V0-64-30fec3fcc5db9170-1"
     assert ic.iscc_id.incr_iscc_id_v0("MAADB7WD7TC5XELQAE") == "MAADB7WD7TC5XELQAI"
+
+
+def test_incr_iscc_id_v0_raises_wrong_mt():
+    mc = ic.Code.rnd(ic.MT.META).code
+    with pytest.raises(AssertionError):
+        ic.incr_iscc_id_v0(mc)
+
+
+def test_incr_iscc_id_v0_raises_wrong_vs():
+    mc = ic.Code.rnd(ic.MT.ID)
+    head = list(mc._head)
+    head[2] = 1
+    mc._head = tuple(head)
+    with pytest.raises(AssertionError):
+        ic.incr_iscc_id_v0(mc.code)
+
+
+def test_gen_iscc_id_v0_raises_chain_id():
+    code = ic.Code.rnd(ic.MT.ISCC, bits=256)
+    with pytest.raises(AssertionError):
+        ic.gen_iscc_id_v0(5, code.code)
diff --git a/tests/test_minhash.py b/tests/test_minhash.py
index c13f5af..9b88e38 100644
--- a/tests/test_minhash.py
+++ b/tests/test_minhash.py
@@ -9,7 +9,7 @@ def test_minhash_empty():
 
 
 def test_minhash_single_feature():
-    mh = ic.minhash([2 ** 16])
+    mh = ic.minhash([2**16])
     assert isinstance(mh, list)
     assert len(mh) == 64
     assert mh[0] == 1968499307
@@ -17,14 +17,14 @@ def test_minhash_single_feature():
 
 
 def test_minhash_32bit_features():
-    i32 = 2 ** 32 - 1
-    mh = ic.minhash([2 ** 64 - 1])
+    i32 = 2**32 - 1
+    mh = ic.minhash([2**64 - 1])
     for n in mh:
         assert n <= i32
 
 
 def test_minhash_compress():
-    mh = ic.minhash([2 ** 16])
+    mh = ic.minhash([2**16])
     digest = ic.compress(mh)
     assert len(digest) == 32
     assert digest.hex() == "a18e2fb2bd663d21db9c7dcc9ae78380253cae5bf089766d87a6b51fcb3f8f8e"
@@ -35,5 +35,5 @@ def test_minhash_compress():
 
 
 def test_minhash_64():
-    mh = ic.minhash_64([2 ** 16])
+    mh = ic.minhash_64([2**16])
     assert mh.hex() == "a18e2fb2bd663d21"
diff --git a/tests/test_simhash.py b/tests/test_simhash.py
index 6422f33..7b59999 100644
--- a/tests/test_simhash.py
+++ b/tests/test_simhash.py
@@ -3,34 +3,34 @@
 
 
 def test_similarity_hash():
-    all_zero = 0b0 .to_bytes(8, "big")
+    all_zero = 0b0.to_bytes(8, "big")
     assert iscc_core.simhash.similarity_hash([all_zero, all_zero]) == all_zero
 
-    all_ones = 0b11111111 .to_bytes(1, "big")
+    all_ones = 0b11111111.to_bytes(1, "big")
     assert iscc_core.simhash.similarity_hash([all_ones, all_ones]) == all_ones
 
-    a = 0b0110 .to_bytes(1, "big")
-    b = 0b1100 .to_bytes(1, "big")
-    r = 0b1110 .to_bytes(1, "big")
+    a = 0b0110.to_bytes(1, "big")
+    b = 0b1100.to_bytes(1, "big")
+    r = 0b1110.to_bytes(1, "big")
     assert iscc_core.simhash.similarity_hash([a, b]) == r
 
-    a = 0b01101001 .to_bytes(1, "big")
-    b = 0b00111000 .to_bytes(1, "big")
-    c = 0b11100100 .to_bytes(1, "big")
-    r = 0b01101000 .to_bytes(1, "big")
+    a = 0b01101001.to_bytes(1, "big")
+    b = 0b00111000.to_bytes(1, "big")
+    c = 0b11100100.to_bytes(1, "big")
+    r = 0b01101000.to_bytes(1, "big")
     assert iscc_core.simhash.similarity_hash([a, b, c]) == r
 
-    a = 0b01100101 .to_bytes(1, "big")
-    b = 0b01011001 .to_bytes(1, "big")
-    c = 0b10010101 .to_bytes(1, "big")
-    d = 0b10101001 .to_bytes(1, "big")
-    r = 0b11111101 .to_bytes(1, "big")
+    a = 0b01100101.to_bytes(1, "big")
+    b = 0b01011001.to_bytes(1, "big")
+    c = 0b10010101.to_bytes(1, "big")
+    d = 0b10101001.to_bytes(1, "big")
+    r = 0b11111101.to_bytes(1, "big")
     assert iscc_core.simhash.similarity_hash([a, b, c, d]) == r
 
-    a = 0b0110100101101001 .to_bytes(2, "big")
-    b = 0b0011100000111000 .to_bytes(2, "big")
-    c = 0b1110010011100100 .to_bytes(2, "big")
-    r = 0b0110100001101000 .to_bytes(2, "big")
+    a = 0b0110100101101001.to_bytes(2, "big")
+    b = 0b0011100000111000.to_bytes(2, "big")
+    c = 0b1110010011100100.to_bytes(2, "big")
+    r = 0b0110100001101000.to_bytes(2, "big")
     assert iscc_core.simhash.similarity_hash([a, b, c]) == r
 
 
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 588e201..db47ef7 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import io
+import os
 
 import pytest
 import iscc_core as ic
@@ -110,3 +111,14 @@ def test_ipfs_hash_raises(static_bytes):
 
 def test_canonicalize():
     assert ic.canonicalize({"hello": "wörld"}) == b'{"hello":"w\xc3\xb6rld"}'
+
+
+def test_sliding_window_raises():
+    with pytest.raises(AssertionError):
+        ic.sliding_window([1, 2, 3, 4, 5], 1)
+
+
+def test_hamming_distance_raises():
+    a, b = os.urandom(8), os.urandom(9)
+    with pytest.raises(AssertionError):
+        ic.hamming_distance(a, b)