diff --git a/pycardano/transaction.py b/pycardano/transaction.py
index 2c4d2909..d95967ed 100644
--- a/pycardano/transaction.py
+++ b/pycardano/transaction.py
@@ -88,6 +88,7 @@ def normalize(self) -> Asset:
         for k, v in list(self.items()):
             if v == 0:
                 self.pop(k)
+
         return self
 
     def union(self, other: Asset) -> Asset:
@@ -425,11 +426,6 @@ def __post_init__(self):
 
     def validate(self):
         super().validate()
-        if isinstance(self.amount, int) and self.amount < 0:
-            raise InvalidDataException(
-                f"Transaction output cannot have negative amount of ADA or "
-                f"native asset: \n {self.amount}"
-            )
         if isinstance(self.amount, Value) and (
             self.amount.coin < 0
             or self.amount.multi_asset.count(lambda p, n, v: v < 0) > 0
@@ -441,10 +437,7 @@ def validate(self):
 
     @property
     def lovelace(self) -> int:
-        if isinstance(self.amount, int):
-            return self.amount
-        else:
-            return self.amount.coin
+        return self.amount.coin
 
     def to_primitive(self) -> Primitive:
         if self.datum or self.script or self.post_alonzo:
diff --git a/test/pycardano/test_transaction.py b/test/pycardano/test_transaction.py
index 5ec6f51e..8428c456 100644
--- a/test/pycardano/test_transaction.py
+++ b/test/pycardano/test_transaction.py
@@ -33,6 +33,16 @@ def test_transaction_input():
     check_two_way_cbor(tx_in)
 
 
+def test_hashable_transaction_input():
+    my_inputs = {}
+    tx_id_hex1 = "732bfd67e66be8e8288349fcaaa2294973ef6271cc189a239bb431275401b8e5"
+    tx_id_hex2 = "732bfd67e66be8e8288349fcaaa2294973ef6271cc189a239bb431275401b8e5"
+    tx_in1 = TransactionInput(TransactionId(bytes.fromhex(tx_id_hex1)), 0)
+    tx_in2 = TransactionInput(TransactionId(bytes.fromhex(tx_id_hex2)), 0)
+    assert tx_in1 == tx_in2
+    my_inputs[tx_in1] = 1
+
+
 def test_transaction_output():
     addr = Address.decode(
         "addr_test1vrm9x2zsux7va6w892g38tvchnzahvcd9tykqf3ygnmwtaqyfg52x"
@@ -133,7 +143,7 @@ def test_invalid_transaction_output():
     addr = Address.decode(
         "addr_test1vrm9x2zsux7va6w892g38tvchnzahvcd9tykqf3ygnmwtaqyfg52x"
     )
-    output = TransactionOutput(addr, -100000000000)
+    output = TransactionOutput(addr, -1)
     with pytest.raises(InvalidDataException):
         output.to_cbor_hex()
 
@@ -266,15 +276,26 @@ def test_multi_asset_addition():
         }
     )
 
+    result = a.union(b)
+
     assert a + b == MultiAsset.from_primitive(
         {
             b"1" * SCRIPT_HASH_SIZE: {b"Token1": 11, b"Token2": 22},
             b"2" * SCRIPT_HASH_SIZE: {b"Token1": 1, b"Token2": 2},
         }
     )
+
+    assert result == MultiAsset.from_primitive(
+        {
+            b"1" * SCRIPT_HASH_SIZE: {b"Token1": 11, b"Token2": 22},
+            b"2" * SCRIPT_HASH_SIZE: {b"Token1": 1, b"Token2": 2},
+        }
+    )
+
     assert a == MultiAsset.from_primitive(
         {b"1" * SCRIPT_HASH_SIZE: {b"Token1": 1, b"Token2": 2}}
     )
+
     assert b == MultiAsset.from_primitive(
         {
             b"1" * SCRIPT_HASH_SIZE: {b"Token1": 10, b"Token2": 20},
@@ -305,6 +326,7 @@ def test_multi_asset_subtraction():
     assert a == MultiAsset.from_primitive(
         {b"1" * SCRIPT_HASH_SIZE: {b"Token1": 1, b"Token2": 2}}
     )
+
     assert b == MultiAsset.from_primitive(
         {
             b"1" * SCRIPT_HASH_SIZE: {b"Token1": 10, b"Token2": 20},
@@ -329,6 +351,10 @@ def test_asset_comparison():
 
     d = Asset.from_primitive({b"Token3": 1, b"Token4": 2})
 
+    result = a.union(b)
+
+    assert result == Asset.from_primitive({b"Token1": 2, b"Token2": 5})
+
     assert a == a
 
     assert a <= b
@@ -341,6 +367,8 @@ def test_asset_comparison():
 
     assert not any([a == d, a <= d, d <= a])
 
+    assert not a == "abc"
+
     with pytest.raises(TypeCheckError):
         a <= 1
 
@@ -381,6 +409,8 @@ def test_multi_asset_comparison():
     assert not a <= d
     assert not d <= a
 
+    assert not a == "abc"
+
     with pytest.raises(TypeCheckError):
         a <= 1
 
@@ -414,6 +444,8 @@ def test_values():
     assert b <= c
     assert not c <= b
 
+    assert not a == "abc"
+
     assert b - a == Value.from_primitive(
         [10, {b"1" * SCRIPT_HASH_SIZE: {b"Token1": 10, b"Token2": 20}}]
     )
@@ -452,6 +484,18 @@ def test_values():
         ]
     )
 
+    result = a.union(b)
+
+    assert result == Value.from_primitive(
+        [12, {b"1" * SCRIPT_HASH_SIZE: {b"Token1": 12, b"Token2": 24}}]
+    )
+
+    d = 10000000
+
+    f = Value(1)
+
+    assert f <= d
+
 
 def test_inline_datum_serdes():
     @dataclass