Add additional test cases for download_data.py.

Author: niklasniedermeier

src/backtest_bay/data/download_data.py

@@ -22,11 +22,14 @@ def _validate_symbol(symbol):
     is_symbol_string = isinstance(symbol, str)
     if not is_symbol_string:
         error_msg = "Symbol must be a non-empty string."
-        raise ValueError(error_msg)
+        raise TypeError(error_msg)
 
     is_symbol_existent = not yf.Ticker(symbol).history(period="1d").empty
     if not is_symbol_existent:
-        error_msg = f"Invalid symbol: '{symbol}'. Please provide a valid ticker symbol."
+        error_msg = (
+            f"Invalid symbol: '{symbol}'. Please provide a valid ticker symbol "
+            "from https://finance.yahoo.com/"
+        )
         raise ValueError(error_msg)
 
 
@@ -52,6 +55,9 @@ def _validate_interval(interval):
 
 
 def _validate_date_format(date_str):
+    if not isinstance(date_str, str):
+        error_msg = "Date must be a string in 'YYYY-MM-DD' format."
+        raise TypeError(error_msg)
     try:
         datetime.fromisoformat(date_str)
     except ValueError as e:

src/backtest_bay/test_download_data.py

@@ -0,0 +1,94 @@
+import pytest
+
+from backtest_bay.data.download_data import (
+    _validate_date_format,
+    _validate_interval,
+    _validate_symbol,
+)
+
+
+# Tests for _validate_symbol
+def test_validate_symbol_valid_cases():
+    _validate_symbol("AAPL")
+    _validate_symbol("MSFT")
+
+
+def test_validate_symbol_invalid_invalid_symbol():
+    with pytest.raises(ValueError, match="Invalid symbol: 'INVALID'"):
+        _validate_symbol("INVALID")
+
+
+def test_validate_symbol_invalid_empty_string():
+    with pytest.raises(ValueError, match="Invalid symbol: ''"):
+        _validate_symbol("")
+
+
+def test_validate_symbol_invalid_non_string():
+    with pytest.raises(TypeError, match="Symbol must be a non-empty string."):
+        _validate_symbol(123)
+
+
+# Tests for _validate_date_format
+@pytest.mark.parametrize(
+    "interval",
+    [
+        "1m",
+        "2m",
+        "5m",
+        "15m",
+        "30m",
+        "60m",
+        "90m",
+        "1h",
+        "1d",
+        "5d",
+        "1wk",
+        "1mo",
+        "3mo",
+    ],
+)
+def test_validate_interval_valid(interval):
+    _validate_interval(interval)
+
+
+def test_validate_interval_invalid():
+    with pytest.raises(ValueError, match="Invalid interval.*"):
+        _validate_interval("10m")
+
+
+@pytest.mark.parametrize("invalid_interval", [None, "", " "])
+def test_validate_interval_edge_cases(invalid_interval):
+    with pytest.raises(ValueError, match="Invalid interval.*"):
+        _validate_interval(invalid_interval)
+
+
+# tests for _validate_date_format
+@pytest.mark.parametrize(
+    "valid_date",
+    [
+        "2023-01-01",
+        "1999-12-31",
+        "2024-02-29",  # Leap year
+    ],
+)
+def test_validate_date_format_valid(valid_date):
+    _validate_date_format(valid_date)
+
+
+@pytest.mark.parametrize(
+    "invalid_date",
+    [
+        "01-01-2023",  # Incorrect format
+        "2023-13-01",  # Invalid month
+        "2023-02-30",  # Invalid day
+    ],
+)
+def test_validate_date_format_invalid(invalid_date):
+    with pytest.raises(ValueError, match="Date must be in 'YYYY-MM-DD' format."):
+        _validate_date_format(invalid_date)
+
+
+def test_validate_date_format_non_string():
+    match = "Date must be a string in 'YYYY-MM-DD' format."
+    with pytest.raises(TypeError, match=match):
+        _validate_date_format(12345)