test: add format_duration test

tests/util/test_formatters.py

@@ -1,5 +1,6 @@
-from freqtrade.util import decimals_per_coin, fmt_coin, round_value
-from freqtrade.util.formatters import fmt_coin2
+from datetime import timedelta
+
+from freqtrade.util import decimals_per_coin, fmt_coin, fmt_coin2, format_duration, round_value
 
 
 def test_decimals_per_coin():
@@ -45,3 +46,12 @@ def test_round_value():
     assert round_value(0.1274512123, 5) == "0.12745"
     assert round_value(222.2, 3, True) == "222.200"
     assert round_value(222.2, 0, True) == "222"
+
+
+def test_format_duration():
+    assert format_duration(timedelta(minutes=5)) == "0d 00:05"
+    assert format_duration(timedelta(minutes=75)) == "0d 01:15"
+    assert format_duration(timedelta(minutes=1440)) == "1d 00:00"
+    assert format_duration(timedelta(minutes=1445)) == "1d 00:05"
+    assert format_duration(timedelta(minutes=11445)) == "7d 22:45"
+    assert format_duration(timedelta(minutes=101445)) == "70d 10:45"