diff --git a/tests/test_pysnooper.py b/tests/test_pysnooper.py
index 49ab4db..88cf625 100644
--- a/tests/test_pysnooper.py
+++ b/tests/test_pysnooper.py
@@ -5,6 +5,7 @@ import io
 import textwrap
 import threading
 import types
+import os
 import sys
 
 from pysnooper.utils import truncate
@@ -1172,3 +1173,57 @@ def test_custom_repr():
             ReturnValueEntry('49995000'),
         )
     )
+
+
+def test_activate_deactivate_snoop():
+    string_io = io.StringIO()
+
+    def my_function(foo):
+        x = 7
+        y = 8
+        return x + y
+
+    os.environ['PYSNOOPER_DISABLED'] = '1'
+    with pysnooper.snoop():
+        result = my_function('baba')
+    output = string_io.getvalue()
+    assert output == ""
+
+    os.environ['PYSNOOPER_DISABLED'] = ''
+    test_string_io()
+
+
+def test_setup_snoop_global():
+    my_snoop = pysnooper.snoop.setup(disable=False)
+    os.environ['PYSNOOPER_DISABLED'] = '1'
+
+    @my_snoop()
+    def my_function(foo):
+        x = 7
+        y = 8
+        return y + x
+
+    with mini_toolbox.OutputCapturer(stdout=False,
+                                     stderr=True) as output_capturer:
+        result = my_function('baba')
+    output = output_capturer.string_io.getvalue()
+    assert_output(
+        output,
+        (
+            VariableEntry('foo', value_regex="u?'baba'"),
+            CallEntry('def my_function(foo):'),
+            LineEntry('x = 7'),
+            VariableEntry('x', '7'),
+            LineEntry('y = 8'),
+            VariableEntry('y', '8'),
+            LineEntry('return y + x'),
+            ReturnEntry('return y + x'),
+            ReturnValueEntry('15'),
+        )
+    )
+
+
+def test_mismatch_parameters_in_setup():
+    with pytest.raises(Exception, match='contain non-snoop parameters') as excinfo:
+        my_snoop = pysnooper.snoop.setup(disabled=False)
+