add tests for upper_to_lowercase rule

tests/rules/test_upper_to_lowercase.py

@@ -0,0 +1,47 @@
+import pytest
+
+from thefuck.rules.upper_to_lowercase import match, get_new_command
+from thefuck.types import Command
+
+
+
+@pytest.mark.parametrize(
+    "script, output",
+    [
+        ("LS", ""),
+        ("CD THEFUCK", ""),
+        ("CAT README.MD", ""),
+        ("MV TESTS TESTING", ""),
+        ("GIT ADD .", ""),
+    ],
+)
+def test_match(script, output):
+    assert match(Command(script, output))
+
+
+@pytest.mark.parametrize(
+    "script, output",
+    [
+        ("ls", ""),
+        ("cd thefuck", ""),
+        ("cat README.md", ""),
+        ("mv tests testing", ""),
+        ("git add .", ""),
+    ],
+)
+def test_not_match(script, output):
+    assert not match(Command(script, output))
+
+
+@pytest.mark.parametrize(
+    "script, output, new_command",
+    [
+        ("LS", "", "ls"),
+        ("CD THEFUCK", "", "cd thefuck"),
+        ("CAT README.MD", "", "cat readme.md"),
+        ("MV TESTS TESTING", "", "mv tests testing"),
+        ("GIT ADD .", "", "git add ."),
+    ],
+)
+def test_get_new_command(script, output, new_command):
+    assert get_new_command(Command(script, output)) == new_command