NewNormal and tests

dist/uv/normal.go

@@ -1,6 +1,7 @@
 package uv
 
 import (
+	"errors"
 	"math"
 
 	"gonum.org/v1/gonum/mathext"
@@ -12,6 +13,20 @@ type Normal struct {
 	Scale    float64
 }
 
+// NewNormal checks the input parameters and returns a Normal constructed
+// using them, if they are valid.
+func NewNormal(location, scale float64) (n *Normal, err error) {
+	if scale <= 0 {
+		err := errors.New("scale must be strictly greater than zero")
+		return nil, err
+	}
+	n = &Normal{
+		Location: location,
+		Scale:    scale,
+	}
+	return n, nil
+}
+
 // Mean returns the first moment of the distribution.
 func (n *Normal) Mean() float64 {
 	return n.Location

dist/uv/normal_test.go

@@ -0,0 +1,55 @@
+package uv_test
+
+import (
+	"testing"
+
+	"github.com/chulabs/seer/dist/uv"
+)
+
+func TestNewNormal(t *testing.T) {
+	tt := []struct {
+		name  string
+		loc   float64
+		scale float64
+	}{
+		{"standard", 0, 1},
+		{"negative loc", -10, 2},
+	}
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			n, err := uv.NewNormal(tc.loc, tc.scale)
+			if err != nil {
+				t.Error("unexpected error in NewNormal,", err)
+			}
+			if n.Location != tc.loc {
+				t.Errorf("expected location %v, but got %v", n.Location, tc.loc)
+			}
+			if n.Scale != tc.scale {
+				t.Errorf("expected Scale %v, but got %v", n.Scale, tc.scale)
+			}
+
+		})
+	}
+}
+
+func TestNewNormalErrs(t *testing.T) {
+	tt := []struct {
+		name  string
+		loc   float64
+		scale float64
+	}{
+		{"zero scale", 10, 0},
+		{"negative scale", 10, -2},
+	}
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			n, err := uv.NewNormal(tc.loc, tc.scale)
+			if err == nil {
+				t.Error("expected error, but it was nil")
+			}
+			if n != nil {
+				t.Error("expected nil dist but it was", n)
+			}
+		})
+	}
+}