diff --git a/checkout_sdk/exception.py b/checkout_sdk/exception.py
index 32c5aee..4c0419b 100644
--- a/checkout_sdk/exception.py
+++ b/checkout_sdk/exception.py
@@ -7,6 +7,8 @@
 class CheckoutException(Exception):
 
     def __init__(self, message=None):
+        if message is None:
+            message = ""
         super().__init__(message)
 
 
@@ -37,8 +39,15 @@ class CheckoutApiException(CheckoutException):
     def __init__(self, response):
         self.http_metadata = map_to_http_metadata(response)
         if response.text:
-            payload = response.json()
-            self.error_details = payload['error_codes'] if 'error_codes' in payload else None
-            self.error_type = payload['error_type'] if 'error_type' in payload else None
+            try:
+                payload = response.json()
+                self.error_details = payload.get('error_codes')
+                self.error_type = payload.get('error_type')
+            except ValueError:
+                self.error_details = None
+                self.error_type = None
+        else:
+            self.error_details = None
+            self.error_type = None
         super().__init__('The API response status code ({}) does not indicate success.'
                          .format(response.status_code))
diff --git a/tests/exception_test.py b/tests/exception_test.py
index c81213d..6ee5d7b 100644
--- a/tests/exception_test.py
+++ b/tests/exception_test.py
@@ -7,35 +7,60 @@
     CheckoutApiException
 )
 from checkout_sdk.authorization_type import AuthorizationType
+from checkout_sdk.utils import map_to_http_metadata
 
 
 def test_checkout_exception():
-    with pytest.raises(CheckoutException):
+    with pytest.raises(CheckoutException) as exc_info:
         raise CheckoutException("Test message")
+    exception = exc_info.value
+    assert str(exception) == "Test message"
 
 
 def test_checkout_argument_exception():
-    with pytest.raises(CheckoutArgumentException):
+    with pytest.raises(CheckoutArgumentException) as exc_info:
         raise CheckoutArgumentException("Argument error occurred")
+    exception = exc_info.value
+    assert str(exception) == "Argument error occurred"
+
+
+def test_checkout_argument_exception_no_message():
+    with pytest.raises(CheckoutArgumentException) as exc_info:
+        raise CheckoutArgumentException()
+    exception = exc_info.value
+    assert str(exception) == ""
 
 
 def test_checkout_authorization_exception():
-    with pytest.raises(CheckoutAuthorizationException):
+    with pytest.raises(CheckoutAuthorizationException) as exc_info:
         raise CheckoutAuthorizationException("Authorization error occurred")
+    exception = exc_info.value
+    assert str(exception) == "Authorization error occurred"
 
 
 def test_invalid_authorization():
     auth_type = Mock(spec=AuthorizationType)
     auth_type.name = "SECRET_KEY"
-    with pytest.raises(CheckoutAuthorizationException, match="SECRET_KEY authorization type"):
+    with pytest.raises(CheckoutAuthorizationException) as exc_info:
         CheckoutAuthorizationException.invalid_authorization(auth_type)
+    assert "SECRET_KEY authorization type" in str(exc_info.value)
 
 
 def test_invalid_key():
     key_type = Mock(spec=AuthorizationType)
     key_type.name = "PUBLIC_KEY"
-    with pytest.raises(CheckoutAuthorizationException, match="PUBLIC_KEY is required for this operation"):
+    with pytest.raises(CheckoutAuthorizationException) as exc_info:
         CheckoutAuthorizationException.invalid_key(key_type)
+    assert "PUBLIC_KEY is required for this operation" in str(exc_info.value)
+
+
+@pytest.mark.parametrize("auth_type_name", ["SECRET_KEY", "PUBLIC_KEY", "CUSTOM_KEY"])
+def test_invalid_authorization_various_types(auth_type_name):
+    auth_type = Mock(spec=AuthorizationType)
+    auth_type.name = auth_type_name
+    with pytest.raises(CheckoutAuthorizationException) as exc_info:
+        CheckoutAuthorizationException.invalid_authorization(auth_type)
+    assert f"{auth_type_name} authorization type" in str(exc_info.value)
 
 
 def test_checkout_api_exception():
@@ -47,12 +72,106 @@ def test_checkout_api_exception():
         "error_codes": ["invalid_field"]
     }
 
-    exception_instance = CheckoutApiException(response)
-
     with pytest.raises(CheckoutApiException) as exc_info:
-        raise exception_instance
-
+        raise CheckoutApiException(response)
     exception = exc_info.value
     assert exception.http_metadata.status_code == 400
     assert exception.error_type == "request_invalid"
     assert exception.error_details == ["invalid_field"]
+
+
+def test_checkout_api_exception_without_error_details():
+    response = Mock()
+    response.status_code = 500
+    response.text = '{"message": "Internal Server Error"}'
+    response.json.return_value = {
+        "message": "Internal Server Error"
+    }
+
+    with pytest.raises(CheckoutApiException) as exc_info:
+        raise CheckoutApiException(response)
+    exception = exc_info.value
+    assert exception.http_metadata.status_code == 500
+    assert exception.error_type is None
+    assert exception.error_details is None
+
+
+def test_checkout_api_exception_empty_response():
+    response = Mock()
+    response.status_code = 404
+    response.text = ''
+    response.json.return_value = {}
+
+    with pytest.raises(CheckoutApiException) as exc_info:
+        raise CheckoutApiException(response)
+    exception = exc_info.value
+    assert exception.http_metadata.status_code == 404
+    assert exception.error_type is None
+    assert exception.error_details is None
+
+
+def test_checkout_api_exception_non_json_response():
+    response = Mock()
+    response.status_code = 502
+    response.text = 'Bad Gateway'
+    response.json.side_effect = ValueError("No JSON object could be decoded")
+
+    with pytest.raises(CheckoutApiException) as exc_info:
+        raise CheckoutApiException(response)
+    exception = exc_info.value
+    assert exception.http_metadata.status_code == 502
+    assert exception.error_type is None
+    assert exception.error_details is None
+
+
+@pytest.mark.parametrize("status_code", [400, 401, 403, 404, 500])
+def test_checkout_api_exception_various_status_codes(status_code):
+    response = Mock()
+    response.status_code = status_code
+    response.text = ''
+    response.json.return_value = {}
+
+    with pytest.raises(CheckoutApiException) as exc_info:
+        raise CheckoutApiException(response)
+    exception = exc_info.value
+    assert exception.http_metadata.status_code == status_code
+
+
+def test_map_to_http_metadata():
+    response = Mock()
+    response.status_code = 200
+    response.headers = {'Content-Type': 'application/json'}
+
+    metadata = map_to_http_metadata(response)
+    assert metadata.status_code == 200
+    assert metadata.headers == {'Content-Type': 'application/json'}
+
+
+def test_checkout_api_exception_message():
+    response = Mock()
+    response.status_code = 400
+    response.text = '{"error_type": "invalid_request", "error_codes": ["bad_request"]}'
+    response.json.return_value = {
+        "error_type": "invalid_request",
+        "error_codes": ["bad_request"]
+    }
+
+    with pytest.raises(CheckoutApiException) as exc_info:
+        raise CheckoutApiException(response)
+    exception = exc_info.value
+    expected_message = "The API response status code (400) does not indicate success."
+    assert str(exception) == expected_message
+
+
+def test_checkout_api_exception_no_response_text():
+    response = Mock()
+    response.status_code = 400
+    response.text = None
+    response.json.return_value = {}
+
+    with pytest.raises(CheckoutApiException) as exc_info:
+        raise CheckoutApiException(response)
+    exception = exc_info.value
+    assert exception.http_metadata.status_code == 400
+    assert exception.error_type is None
+    assert exception.error_details is None