chore: optimize coding style and add unit tests (#3917)

core/mathx/entropy_test.go

@@ -15,3 +15,17 @@ func TestCalcEntropy(t *testing.T) {
 	}
 	assert.True(t, CalcEntropy(m) > .99)
 }
+
+func TestCalcEmptyEntropy(t *testing.T) {
+	m := make(map[any]int)
+	assert.Equal(t, float64(1), CalcEntropy(m))
+}
+
+func TestCalcDiffEntropy(t *testing.T) {
+	const total = 1000
+	m := make(map[any]int, total)
+	for i := 0; i < total; i++ {
+		m[i] = i
+	}
+	assert.True(t, CalcEntropy(m) < .99)
+}