check other cases and add test_rsa.py

tests/core/crypto/test_rsa.py

@@ -0,0 +1,30 @@
+import pytest
+
+from libp2p.crypto.exceptions import (
+    CryptographyError,
+)
+from libp2p.crypto.rsa import (
+    MAX_RSA_KEY_SIZE,
+    RSAPrivateKey,
+    validate_rsa_key_size,
+)
+
+
+def test_validate_rsa_key_size():
+    # Test valid key size
+    key = RSAPrivateKey.new(2048)
+    validate_rsa_key_size(key.impl)
+
+    # Test key size too large
+    with pytest.raises(
+        CryptographyError, match=f".*exceeds maximum allowed size {MAX_RSA_KEY_SIZE}"
+    ):
+        RSAPrivateKey.new(MAX_RSA_KEY_SIZE + 1)
+
+    # Test negative key size (this would be caught when creating the key)
+    with pytest.raises(CryptographyError, match="RSA key size must be positive"):
+        RSAPrivateKey.new(-1)
+
+    # Test zero key size
+    with pytest.raises(CryptographyError, match="RSA key size must be positive"):
+        RSAPrivateKey.new(0)