diff --git a/tests/conftest.py b/tests/conftest.py
index 6798f60..f0ff077 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -2,6 +2,30 @@
 from utils import vcr_kwargs, DEFAULT_OUTPUT_FOLDER
 
 
+# Pytest configurations. Modified from
+# https://docs.pytest.org/en/7.1.x/example/simple.html#control-skipping-of-tests-according-to-command-line-option
+
+# Add option for CLI invocation
+def pytest_addoption(parser):
+    parser.addoption(
+        "--skip-slow", action="store_true", default=False, help="skip slow tests"
+    )
+
+
+# Register pytest.mark.slow
+def pytest_configure(config):
+    config.addinivalue_line("markers", "slow: mark test as slow to run")
+
+
+# Skip slow tests unless --run_slow is given
+def pytest_collection_modifyitems(config, items):
+    if config.getoption("--skip-slow"):
+        skip_slow = pytest.mark.skip(reason="skipped due to --skip-slow")
+        for item in items:
+            if "slow" in item.keywords:
+                item.add_marker(skip_slow)
+
+
 # Configuration fixture for pytest-vcr
 @pytest.fixture(scope="session")
 def vcr_config():
diff --git a/tests/test_get_historical_data.py b/tests/test_get_historical_data.py
index f156243..d15dc88 100644
--- a/tests/test_get_historical_data.py
+++ b/tests/test_get_historical_data.py
@@ -9,16 +9,17 @@
 )
 
 
+# Filterwarnings from: https://stackoverflow.com/a/58645998/11316205
 @pytest.mark.vcr
-@pytest.mark.filterwarnings(
-    "ignore::UserWarning"
-)  # https://stackoverflow.com/a/58645998/11316205
+@pytest.mark.slow
+@pytest.mark.filterwarnings("ignore::UserWarning")
 def test_return_value_and_format():
     result = api.get_historical_data(city="london")
     assert isinstance(result, pandas.DataFrame)
 
 
 @pytest.mark.vcr
+@pytest.mark.slow
 def test_warnings_on_input_combo():
     with pytest.warns(UserWarning, match="city_id was not supplied"):
         api.get_historical_data(city="london")
@@ -37,6 +38,7 @@ def test_arguments_not_named():
 
 
 @pytest.mark.vcr
+@pytest.mark.slow
 @pytest.mark.parametrize("fmt", SUPPORTED_OUTPUT_FORMATS)
 @pytest.mark.filterwarnings("ignore::UserWarning")
 def test_output_data_formats(fmt):