diff --git a/tests/test_status_codes.py b/tests/test_status_codes.py
new file mode 100644
index 0000000..a9b4e45
--- /dev/null
+++ b/tests/test_status_codes.py
@@ -0,0 +1,67 @@
+import pytest
+from responder import status_codes
+
+
+@pytest.mark.parametrize(
+    "status_code, expected",
+    [
+        pytest.param(101, True, id="Normal 101"),
+        pytest.param(199, True, id="Not actual status code but within 100"),
+        pytest.param(0, False, id="Zero case (below 100)"),
+        pytest.param(200, False, id="Above 100")
+    ],
+)
+def test_is_100(status_code, expected):
+    assert status_codes.is_100(status_code) is expected
+
+
+@pytest.mark.parametrize(
+    "status_code, expected",
+    [
+        pytest.param(201, True, id="Normal 201"),
+        pytest.param(299, True, id="Not actual status code but within 200"),
+        pytest.param(0, False, id="Zero case (below 200)"),
+        pytest.param(300, False, id="Above 200")
+    ],
+)
+def test_is_200(status_code, expected):
+    assert status_codes.is_200(status_code) is expected
+
+
+@pytest.mark.parametrize(
+    "status_code, expected",
+    [
+        pytest.param(301, True, id="Normal 301"),
+        pytest.param(399, True, id="Not actual status code but within 300"),
+        pytest.param(0, False, id="Zero case (below 300)"),
+        pytest.param(400, False, id="Above 300")
+    ],
+)
+def test_is_300(status_code, expected):
+    assert status_codes.is_300(status_code) is expected
+
+
+@pytest.mark.parametrize(
+    "status_code, expected",
+    [
+        pytest.param(401, True, id="Normal 401"),
+        pytest.param(499, True, id="Not actual status code but within 400"),
+        pytest.param(0, False, id="Zero case (below 400)"),
+        pytest.param(500, False, id="Above 400")
+    ],
+)
+def test_is_400(status_code, expected):
+    assert status_codes.is_400(status_code) is expected
+
+
+@pytest.mark.parametrize(
+    "status_code, expected",
+    [
+        pytest.param(501, True, id="Normal 401"),
+        pytest.param(599, True, id="Not actual status code but within 400"),
+        pytest.param(0, False, id="Zero case (below 400)"),
+        pytest.param(600, False, id="Above 500")
+    ],
+)
+def test_is_500(status_code, expected):
+    assert status_codes.is_500(status_code) is expected