diff --git a/amqp/adapter/serializer.py b/amqp/adapter/serializer.py
index a112507..ce70d2e 100644
--- a/amqp/adapter/serializer.py
+++ b/amqp/adapter/serializer.py
@@ -18,7 +18,7 @@ def bytes_to_long(b: bytes) -> int:
 def read_long(bis: BytesIO) -> int:
     try:
         return struct.unpack("q", bis.read(8))[0]
-    except IOError:
+    except struct.error:
         return 0
 
 
@@ -51,7 +51,10 @@ def csv_as_list(input_str: str) -> List[str]:
 
 
 def add_to_map(map_: Dict[str, List[str]], token: str) -> None:
-    eq_idx = token.index("=")
+    try:
+        eq_idx = token.index("=")
+    except ValueError:
+        eq_idx = -1  # set to -1 when not found
     if eq_idx > 0:
         key = token[:eq_idx]
         map_[key] = csv_as_list(token[eq_idx + 1 :])
diff --git a/tests/adapter/test_serializer.py b/tests/adapter/test_serializer.py
index d15a91f..3c3bc03 100644
--- a/tests/adapter/test_serializer.py
+++ b/tests/adapter/test_serializer.py
@@ -1,42 +1,114 @@
-def test_long_to_bytes():
-    assert False
+import unittest
+from io import BytesIO
+
+from amqp.adapter.serializer import (
+    bytes_to_long,
+    csv_as_list,
+    long_to_bytes,
+    map_as_string,
+    map_with_list_as_string,
+    object_or_list_as_string,
+    parse_map_list_string,
+    parse_map_string,
+    read_long,
+    str_to_bool,
+)
 
 
-def test_bytes_to_long():
-    assert False
+class TestSerializer(unittest.TestCase):
+    def test_long_to_bytes_and_bytes_to_long(self):
+        # Test conversion in both directions
+        test_numbers = [
+            -9223372036854775808,
+            -1,
+            0,
+            1,
+            9223372036854775807,
+        ]  # Min and max long values
+        for num in test_numbers:
+            bytes_val = long_to_bytes(num)
+            self.assertEqual(bytes_to_long(bytes_val), num)
 
+    def test_read_long(self):
+        # Test reading valid long
+        test_num = 12345
+        bio = BytesIO(long_to_bytes(test_num))
+        self.assertEqual(read_long(bio), test_num)
 
-def test_read_long():
-    assert False
+        # Test reading from empty BytesIO
+        empty_bio = BytesIO()
+        self.assertEqual(read_long(empty_bio), 0)
 
+    def test_object_or_list_as_string(self):
+        # Test with string
+        self.assertEqual(object_or_list_as_string("test"), "test")
 
-def test_object_or_list_as_string():
-    assert False
+        # Test with list
+        self.assertEqual(object_or_list_as_string(["a", "b", "c"]), "[a,b,c]")
 
+        # Test with empty list
+        self.assertEqual(object_or_list_as_string([]), "[]")
 
-def test_map_as_string():
-    assert False
+    def test_map_as_string(self):
+        # Test with simple key-value pairs
+        test_map = {"key1": "value1", "key2": "value2"}
+        self.assertEqual(map_as_string(test_map), "key1=value1,key2=value2")
 
+        # Test with empty map
+        self.assertEqual(map_as_string({}), "")
 
-def test_map_with_list_as_string():
-    assert False
+    def test_map_with_list_as_string(self):
+        # Test with lists as values
+        test_map = {"key1": ["a", "b"], "key2": ["c", "d"]}
+        self.assertEqual(map_with_list_as_string(test_map), "key1=[a,b],key2=[c,d]")
 
+        # Test with empty map
+        self.assertEqual(map_with_list_as_string({}), "")
 
-def test_parse_map_string():
-    assert False
+    def test_parse_map_string(self):
+        # Test valid map string
+        test_str = "{key1=value1,key2=value2}"
+        expected = {"key1": "value1", "key2": "value2"}
+        self.assertEqual(parse_map_string(test_str), expected)
 
+        # Test empty map string
+        self.assertEqual(parse_map_string("{}"), {})
 
-def test_csv_as_list():
-    assert False
+        # Test invalid format
+        self.assertEqual(parse_map_string("invalid"), {})
 
+    def test_csv_as_list(self):
+        # Test normal CSV string
+        self.assertEqual(csv_as_list("a,b,c"), ["a", "b", "c"])
 
-def test_add_to_map():
-    assert False
+        # Test with spaces
+        self.assertEqual(csv_as_list(" a , b , c "), ["a", "b", "c"])
 
+        # Test with brackets
+        self.assertEqual(csv_as_list("[a,b,c]"), ["a", "b", "c"])
 
-def test_parse_map_list_string():
-    assert False
+        # Test empty list
+        self.assertEqual(csv_as_list("[]"), [""])
 
+    def test_parse_map_list_string(self):
+        # Test valid map list string
+        test_str = "{key1=[a,b],key2=[c,d]}"
+        expected = {"key1": ["a", "b"], "key2": ["c", "d"]}
+        self.assertEqual(parse_map_list_string(test_str), expected)
 
-def test_str_to_bool():
-    assert False
+        # Test empty map
+        self.assertEqual(parse_map_list_string("{}"), {})
+
+        # Test single entry
+        self.assertEqual(parse_map_list_string("{key1=[a,b]}"), {"key1": ["a", "b"]})
+
+    def test_str_to_bool(self):
+        # Test true values
+        true_values = ["true", "yes", "1", "t", "y", "on", "TRUE", "YES", "T", "Y", "ON"]
+        for value in true_values:
+            self.assertTrue(str_to_bool(value))
+
+        # Test false values
+        false_values = ["false", "no", "0", "f", "n", "off", "FALSE", "NO", "F", "N", "OFF"]
+        for value in false_values:
+            self.assertFalse(str_to_bool(value))