Bug fix in RoundFloat func in common/math package (#579)

* refactored RoundFloat func in common/math package

* cleanup

Co-authored-by: Vazha Bezhanishvili <vazha.bezhanishvili@elegro.eu>

common/math/math.go

@@ -31,21 +31,6 @@ func CalculateNetProfit(amount, priceThen, priceNow, costs float64) float64 {
 
 // RoundFloat rounds your floating point number to the desired decimal place
 func RoundFloat(x float64, prec int) float64 {
-	var rounder float64
 	pow := math.Pow(10, float64(prec))
-	intermed := x * pow
-	_, frac := math.Modf(intermed)
-	intermed += .5
-	x = .5
-	if frac < 0.0 {
-		x = -.5
-		intermed--
-	}
-	if frac >= x {
-		rounder = math.Ceil(intermed)
-	} else {
-		rounder = math.Floor(intermed)
-	}
-
-	return rounder / pow
+	return math.Round(x*pow) / pow
 }

common/math/math_test.go

@@ -66,16 +66,37 @@ func TestCalculateNetProfit(t *testing.T) {
 
 func TestRoundFloat(t *testing.T) {
 	t.Parallel()
-	// mapping of input vs expected result
-	testTable := map[float64]float64{
-		2.3232323:  2.32,
-		-2.3232323: -2.32,
+	// mapping of input vs expected result : map[precision]map[testedValue]expectedOutput
+	testTableValues := map[int]map[float64]float64{
+		0: {
+			2.23456789:  2,
+			-2.23456789: -2,
+		},
+		1: {
+			2.23456789:  2.2,
+			-2.23456789: -2.2,
+		},
+		2: {
+			2.23456789:  2.23,
+			-2.23456789: -2.23,
+		},
+		4: {
+			2.23456789:  2.2346,
+			-2.23456789: -2.2346,
+		},
+		8: {
+			2.23456781:  2.23456781,
+			-2.23456781: -2.23456781,
+		},
 	}
-	for testInput, expectedOutput := range testTable {
-		actualOutput := RoundFloat(testInput, 2)
-		if actualOutput != expectedOutput {
-			t.Errorf("RoundFloat Expected '%f'. Actual '%f'.",
-				expectedOutput, actualOutput)
+
+	for precision, values := range testTableValues {
+		for testInput, expectedOutput := range values {
+			actualOutput := RoundFloat(testInput, precision)
+			if actualOutput != expectedOutput {
+				t.Errorf("RoundFloat Expected '%v'. Actual '%v' on precission %d",
+					expectedOutput, actualOutput, precision)
+			}
 		}
 	}
 }