strategy/pivotshort: add trendema test case

pkg/bbgo/trend_ema_test.go

@@ -0,0 +1,21 @@
+package bbgo
+
+import (
+	"testing"
+
+	"github.com/c9s/bbgo/pkg/types"
+)
+
+func Test_TrendEMA(t *testing.T) {
+	t.Run("Test Trend EMA", func(t *testing.T) {
+		trendEMA_test := TrendEMA{
+			IntervalWindow: types.IntervalWindow{Window: 1},
+		}
+		trendEMA_test.last = 1000.0
+		trendEMA_test.current = 1200.0
+
+		if trendEMA_test.Gradient() != 1.2 {
+			t.Errorf("Gradient() = %v, want %v", trendEMA_test.Gradient(), 1.2)
+		}
+	})
+}