diff --git a/tests/helpers.py b/tests/helpers.py
new file mode 100644
index 0000000..55d0d26
--- /dev/null
+++ b/tests/helpers.py
@@ -0,0 +1,9 @@
+
+def mock_urlopen(m):
+    import urllib.request
+    def mock(url):
+        class FakeIO:
+            def read(*args):
+                return "X".encode('utf-8')
+        return FakeIO()
+    m.setattr(urllib.request, "urlopen", mock)
diff --git a/tests/test_fe.py b/tests/test_fe.py
index 956afce..806663f 100644
--- a/tests/test_fe.py
+++ b/tests/test_fe.py
@@ -7,7 +7,10 @@ import pytest
 from facho import fe
 
 
-def test_xmlsigned_build():
+import helpers
+
+
+def test_xmlsigned_build(monkeypatch):
     #openssl req -x509 -sha256 -nodes -subj "/CN=test" -days 1 -newkey rsa:2048 -keyout example.key -out example.pem 
     #openssl pkcs12 -export -out example.p12 -inkey example.key -in example.pem
     signer = fe.DianXMLExtensionSigner('./tests/example.p12')
@@ -15,14 +18,17 @@ def test_xmlsigned_build():
     xml = fe.FeXML('Invoice',
                    'http://www.dian.gov.co/contratos/facturaelectronica/v1')
     xml.add_extension(signer)
-    xml.attach_extensions()
+
+    with monkeypatch.context() as m:
+        helpers.mock_urlopen(m)
+        xml.attach_extensions()
     elem = xml.find_or_create_element('/fe:Invoice/ext:UBLExtensions/ext:UBLExtension/ext:ExtensionContent/ds:Signature')
     
     assert elem is not None
     #assert elem.findall('ds:SignedInfo', fe.NAMESPACES) is not None
 
 
-def test_xmlsigned_with_passphrase_build():
+def test_xmlsigned_with_passphrase_build(monkeypatch):
     #openssl req -x509 -sha256 -nodes -subj "/CN=test" -days 1 -newkey rsa:2048 -keyout example.key -out example.pem 
     #openssl pkcs12 -export -out example.p12 -inkey example.key -in example.pem
     signer = fe.DianXMLExtensionSigner('./tests/example-with-passphrase.p12', 'test')
@@ -30,7 +36,10 @@ def test_xmlsigned_with_passphrase_build():
     xml = fe.FeXML('Invoice',
                    'http://www.dian.gov.co/contratos/facturaelectronica/v1')
     xml.add_extension(signer)
-    xml.attach_extensions()
+    
+    with monkeypatch.context() as m:
+        helpers.mock_urlopen(m)
+        xml.attach_extensions()
     elem = xml.find_or_create_element('/fe:Invoice/ext:UBLExtensions/ext:UBLExtension/ext:ExtensionContent/ds:Signature')
     
     assert elem is not None
diff --git a/tests/test_fe_form.py b/tests/test_fe_form.py
index b039b55..8e674eb 100644
--- a/tests/test_fe_form.py
+++ b/tests/test_fe_form.py
@@ -79,7 +79,7 @@ def test_invoicesimple_build_with_cufe(simple_invoice):
     assert cufe != ''
 
 
-def test_invoicesimple_xml_signed(simple_invoice):
+def test_invoicesimple_xml_signed(monkeypatch, simple_invoice):
     invoice_validator = form.DianResolucion0001Validator()
     simple_invoice.validate(invoice_validator)
     assert invoice_validator.valid() == True
@@ -88,7 +88,10 @@ def test_invoicesimple_xml_signed(simple_invoice):
     signer = fe.DianXMLExtensionSigner('./tests/example.p12')
     xml.add_extension(signer)
 
-    xml.attach_extensions()
+    with monkeypatch.context() as m:
+        import helpers
+        helpers.mock_urlopen(m)
+        xml.attach_extensions()
 
     elem = xml.find_or_create_element('/fe:Invoice/ext:UBLExtensions/ext:UBLExtension/ext:ExtensionContent/ds:Signature')
     assert elem.text is not None