diff --git a/trezor_agent/gpg/tests/__init__.py b/trezor_agent/gpg/tests/__init__.py
new file mode 100644
index 0000000..50c95d5
--- /dev/null
+++ b/trezor_agent/gpg/tests/__init__.py
@@ -0,0 +1 @@
+"""Tests for GPG module."""
diff --git a/trezor_agent/gpg/tests/test_proto.py b/trezor_agent/gpg/tests/test_proto.py
new file mode 100644
index 0000000..7637b15
--- /dev/null
+++ b/trezor_agent/gpg/tests/test_proto.py
@@ -0,0 +1,84 @@
+import ecdsa
+import ed25519
+
+from .. import proto
+from ... import formats
+
+
+def test_packet():
+    assert proto.packet(1, b'') == b'\x84\x00'
+    assert proto.packet(2, b'A') == b'\x88\x01A'
+    blob = b'B' * 0xAB
+    assert proto.packet(3, blob) == b'\x8c\xAB' + blob
+    blob = b'C' * 0x1234
+    assert proto.packet(3, blob) == b'\x8d\x12\x34' + blob
+    blob = b'D' * 0x12345678
+    assert proto.packet(4, blob) == b'\x92\x12\x34\x56\x78' + blob
+
+
+def test_subpackets():
+    assert proto.subpacket(1, b'') == b'\x01'
+    assert proto.subpacket(2, '>H', 0x0304) == b'\x02\x03\x04'
+    assert proto.subpacket_long(9, 0x12345678) == b'\x09\x12\x34\x56\x78'
+    assert proto.subpacket_time(0x12345678) == b'\x02\x12\x34\x56\x78'
+    assert proto.subpacket_byte(0xAB, 0xCD) == b'\xAB\xCD'
+    assert proto.subpackets() == b'\x00\x00'
+    assert proto.subpackets(b'ABC', b'12345') == b'\x00\x0A\x03ABC\x0512345'
+
+
+def test_mpi():
+    assert proto.mpi(0x123) == b'\x00\x09\x01\x23'
+
+
+def test_find():
+    assert proto.find_curve_by_algo_id(19) == formats.CURVE_NIST256
+    assert proto.find_curve_by_algo_id(22) == formats.CURVE_ED25519
+
+
+def test_armor():
+    data = bytearray(range(256))
+    assert proto.armor(data, 'TEST') == '''-----BEGIN PGP TEST-----
+Version: GnuPG v2
+
+AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8gISIjJCUmJygpKissLS4v
+MDEyMzQ1Njc4OTo7PD0+P0BBQkNERUZHSElKS0xNTk9QUVJTVFVWV1hZWltcXV5f
+YGFiY2RlZmdoaWprbG1ub3BxcnN0dXZ3eHl6e3x9fn+AgYKDhIWGh4iJiouMjY6P
+kJGSk5SVlpeYmZqbnJ2en6ChoqOkpaanqKmqq6ytrq+wsbKztLW2t7i5uru8vb6/
+wMHCw8TFxsfIycrLzM3Oz9DR0tPU1dbX2Nna29zd3t/g4eLj5OXm5+jp6uvs7e7v
+8PHy8/T19vf4+fr7/P3+/w==
+=W700
+-----END PGP TEST-----
+'''
+
+
+def test_make_signature():
+    def signer_func(digest):
+        assert digest == (b'\xd0\xe5]|\x8bP\xe6\x91\xb3\xe8+\xf4A\xf0`(\xb1'
+                          b'\xc7\xf4;\x86\x97s\xdb\x9a\xda\xee< \xcb\x9e\x00')
+        return b'SIGNATURE'
+
+    sig = proto.make_signature(
+        signer_func=signer_func,
+        data_to_sign=b'Hello World!',
+        public_algo=22,
+        hashed_subpackets=[proto.subpacket_time(1)],
+        unhashed_subpackets=[],
+        sig_type=25)
+    assert sig == (b'\x04\x19\x16\x08\x00\x06\x05\x02'
+                   b'\x00\x00\x00\x01\x00\x00\xd0\xe5SIGNATURE')
+
+
+def test_nist256p1():
+    sk = ecdsa.SigningKey.from_secret_exponent(secexp=1, curve=ecdsa.NIST256p)
+    vk = sk.get_verifying_key()
+    pk = proto.PublicKey(curve_name=formats.CURVE_NIST256,
+                         created=42, verifying_key=vk)
+    assert repr(pk) == '<E41511BAF82361D9>'
+
+
+def test_ed25519():
+    sk = ed25519.SigningKey(b'\x00' * 32)
+    vk = sk.get_verifying_key()
+    pk = proto.PublicKey(curve_name=formats.CURVE_ED25519,
+                         created=42, verifying_key=vk)
+    assert repr(pk) == '<545170A236B40FE6>'