diff --git a/src/first_filings/cli.py b/src/first_filings/cli.py
index e238988..666d2aa 100644
--- a/src/first_filings/cli.py
+++ b/src/first_filings/cli.py
@@ -36,8 +36,7 @@ def get_date_range(date_obj, period):
         month = ((to_date.month - 1) // 3) * 3 + 1
         from_date = to_date.replace(month=month, day=1)
     else:
-        # Fallback to day
-        from_date = to_date
+        raise ValueError(f"Invalid period: {period}")
 
     return from_date, to_date
 
diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..91d4a51
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,77 @@
+from datetime import datetime
+import pytest
+
+from first_filings.cli import get_date_range
+
+
+def test_get_date_range_day():
+    date_obj = datetime(2023, 10, 25)
+    from_date, to_date = get_date_range(date_obj, "day")
+    assert from_date == date_obj
+    assert to_date == date_obj
+
+
+def test_get_date_range_wtd():
+    # Wednesday
+    date_obj = datetime(2023, 10, 25)
+    from_date, to_date = get_date_range(date_obj, "wtd")
+    # Monday of that week
+    assert from_date == datetime(2023, 10, 23)
+    assert to_date == date_obj
+
+    # Monday
+    date_obj_mon = datetime(2023, 10, 23)
+    from_date_mon, to_date_mon = get_date_range(date_obj_mon, "wtd")
+    assert from_date_mon == datetime(2023, 10, 23)
+    assert to_date_mon == date_obj_mon
+
+    # Sunday
+    date_obj_sun = datetime(2023, 10, 29)
+    from_date_sun, to_date_sun = get_date_range(date_obj_sun, "wtd")
+    assert from_date_sun == datetime(2023, 10, 23)
+    assert to_date_sun == date_obj_sun
+
+
+def test_get_date_range_mtd():
+    date_obj = datetime(2023, 10, 25)
+    from_date, to_date = get_date_range(date_obj, "mtd")
+    assert from_date == datetime(2023, 10, 1)
+    assert to_date == date_obj
+
+    # 1st of the month
+    date_obj_1st = datetime(2023, 10, 1)
+    from_date_1st, to_date_1st = get_date_range(date_obj_1st, "mtd")
+    assert from_date_1st == datetime(2023, 10, 1)
+    assert to_date_1st == date_obj_1st
+
+
+def test_get_date_range_qtd():
+    # Q1: January - March
+    date_obj_q1 = datetime(2023, 2, 15)
+    from_date, to_date = get_date_range(date_obj_q1, "qtd")
+    assert from_date == datetime(2023, 1, 1)
+    assert to_date == date_obj_q1
+
+    # Q2: April - June
+    date_obj_q2 = datetime(2023, 5, 10)
+    from_date, to_date = get_date_range(date_obj_q2, "qtd")
+    assert from_date == datetime(2023, 4, 1)
+    assert to_date == date_obj_q2
+
+    # Q3: July - September
+    date_obj_q3 = datetime(2023, 9, 30)
+    from_date, to_date = get_date_range(date_obj_q3, "qtd")
+    assert from_date == datetime(2023, 7, 1)
+    assert to_date == date_obj_q3
+
+    # Q4: October - December
+    date_obj_q4 = datetime(2023, 12, 31)
+    from_date, to_date = get_date_range(date_obj_q4, "qtd")
+    assert from_date == datetime(2023, 10, 1)
+    assert to_date == date_obj_q4
+
+
+def test_get_date_range_invalid_period():
+    date_obj = datetime(2023, 10, 25)
+    with pytest.raises(ValueError, match="Invalid period: ytd"):
+        get_date_range(date_obj, "ytd")