[wpilib] Add AlertSim function to get only active alerts (#8732)

wpilibc/src/test/python/test_alert.py

@@ -143,3 +143,30 @@ def test_set_text_while_set(group_name):
         assert alert.getText() == "AFTER"
         assert not is_alert_active("BEFORE", Alert.Level.LOW)
         assert is_alert_active("AFTER", Alert.Level.LOW)
+
+def test_get_active(group_name):
+    with (
+        Alert(group_name, "A", Alert.Level.HIGH) as a,
+        Alert(group_name, "B", Alert.Level.HIGH) as b,
+        Alert(group_name, "C", Alert.Level.HIGH) as c,
+    ):
+
+        a.set(True)
+        b.set(True)
+        c.set(False)
+        
+        active = AlertSim.getActive()
+        allAlerts = AlertSim.getAll()
+        
+        assert len(active) == 2
+        assert len(allAlerts) == 3
+
+        activeTexts = [a.text for a in active]
+        assert set(activeTexts) == {"A", "B"}
+
+        a.set(False)
+        active = AlertSim.getActive()
+        allAlerts = AlertSim.getAll()
+        assert len(active) == 1
+        assert len(allAlerts) == 3
+        assert active[0].text == "B"