✅ add unit tests for format_dt

Author: Paillat-dev

tests/test_format_dt.py

@@ -0,0 +1,54 @@
+import datetime
+import random
+import pytest
+from discord.utils import format_dt
+
+# Fix seed so that time tests are reproducible
+random.seed(42)
+
+ALL_STYLES = ["t", "T", "d", "D", "f", "F", "R", None]
+
+DATETIME_CASES = [
+    (datetime.datetime(1970, 1, 1, 0, 0, 0, tzinfo=datetime.timezone.utc), 0),
+    (datetime.datetime(2000, 2, 29, 12, 0, 0, tzinfo=datetime.timezone.utc), 951825600),
+    (datetime.datetime(1999, 12, 31, 23, 59, 59, tzinfo=datetime.timezone.utc), 946684799),
+    (datetime.datetime(2023, 1, 2, 3, 4, 5, tzinfo=datetime.timezone.utc), 1672628645),
+    (datetime.datetime(2050, 6, 15, 7, 30, 0, tzinfo=datetime.timezone.utc), 2538891000),
+]
+
+
+def random_time():
+    return datetime.time(
+        random.randint(0, 23),
+        random.randint(0, 59),
+        random.randint(0, 59),
+    )
+
+
+@pytest.mark.parametrize(("dt", "expected_ts"), DATETIME_CASES)
+@pytest.mark.parametrize("style", ALL_STYLES)
+def test_format_dt_formats_datetime(dt, expected_ts, style):
+    """
+    For each (dt, expected_ts) pair and each style,
+    format_dt should produce the correct Discord timestamp.
+    """
+    if style is None:
+        expected = f"<t:{expected_ts}>"
+    else:
+        expected = f"<t:{expected_ts}:{style}>"
+    result = format_dt(dt, style=style)
+    assert result == expected
+
+
+@pytest.mark.parametrize("style", ALL_STYLES)
+def test_format_dt_formats_time_equivalence(style):
+    """
+    For a time-only input, format_dt(time, style) should equal
+    format_dt(datetime.combine(today, time), style).
+    """
+    tm = random_time()
+    today = datetime.datetime.now().date()
+    result_time = format_dt(tm, style=style)
+    dt = datetime.datetime.combine(today, tm)
+    result_dt = format_dt(dt, style=style)
+    assert result_time == result_dt