diff --git a/tests/unit/manager_test.py b/tests/unit/manager_test.py
index <HASH>..<HASH> 100644
--- a/tests/unit/manager_test.py
+++ b/tests/unit/manager_test.py
@@ -23,3 +23,15 @@ class TestManager:
     @raises(ValueError)
     def test_weather_to_text_invalid_input_String(self):
         weather_text = self.manager._weather_to_text('1')
+        
+    @raises(ValueError)
+    def test_visbility_to_text_invalid_input_None(self):
+        visibility = self.manager._weather_to_text(None)
+
+    @raises(ValueError)
+    def test_visibility_to_text_invalid_input_out_of_bounds(self):
+        visibility = self.manager._weather_to_text(-1)
+
+    @raises(ValueError)
+    def test_visibility_to_text_invalid_input_String(self):
+        visibility = self.manager._weather_to_text('1')
\ No newline at end of file
Add unit tests for Manager._visibility_to_text