Add working tests. Fix issue with min/max.

3 files changed, 76 insertions, 7 deletions

diff --git a/print.go b/print.go
index 8bdeea3..fea1d7d 100644
--- a/print.go
+++ b/print.go
@@ -14,7 +14,7 @@ func (s *Stats) PrettyStats() string {
 	Standard Deviation: %.2f
 	Skewness: %.2f
 	Kurtosis: %.2f
-`, s.Min, s.Max, s.Mean(), s.Variance(), s.StandardDeviation(), s.Skewness(), s.Kurtosis())
+`, s.Min(), s.Max(), s.Mean(), s.Variance(), s.StandardDeviation(), s.Skewness(), s.Kurtosis())
 }
 
 // Returns a string containing all of the data within the struct
diff --git a/stats.go b/stats.go
index 46ddc99..534d24e 100644
--- a/stats.go
+++ b/stats.go
@@ -40,8 +40,7 @@ import (
 // several methods are exposed in order to make your life easy
 type Stats struct {
 	n, m1, m2, m3, m4 float64
-	Max               float64
-	Min               float64
+	max, min          *float64
 }
 
 // Zeros out the  struct for re-use
@@ -55,11 +54,11 @@ func (s *Stats) Clear() {
 func (s *Stats) Push(x float64) {
 	var delta, delta_n, delta_n2, term1, n1 float64
 
-	if x >= s.Max {
-		s.Max = x
+	if s.max == nil || x >= *s.max {
+		s.max = &x
 	}
-	if x <= s.Min {
-		s.Min = x
+	if s.min == nil || x <= *s.min {
+		s.min = &x
 	}
 
 	n1 = s.n
@@ -97,3 +96,11 @@ func (s *Stats) Skewness() float64 {
 func (s *Stats) Kurtosis() float64 {
 	return s.n*s.m4/(s.m2*s.m2) - 3
 }
+
+func (s *Stats) Min() float64 {
+	return *s.min
+}
+
+func (s *Stats) Max() float64 {
+	return *s.max
+}
diff --git a/stats_test.go b/stats_test.go
new file mode 100644
index 0000000..a101270
--- /dev/null
+++ b/stats_test.go
@@ -0,0 +1,62 @@
+package stats
+
+import (
+	"fmt"
+	"math"
+	"reflect"
+	"testing"
+)
+
+var (
+	datasets [][]float64 = [][]float64{
+		// set 0
+		{
+			22.90, 28.55, 36.33, 33.71, 26.29, 34.64, 30.14, 34.31,
+			25.69, 30.09, 28.69, 11.61, 10.68, 24.70, 22.83, 38.08,
+			24.22, 41.08, 29.70, 26.01, 38.47, 40.25,
+		},
+		// set 1
+		{
+			15.054, 19.106, 16.926, 16.243, 20.345, 18.615, 15.050,
+			18.716, 13.691, 18.296, 16.816, 21.415, 20.756, 13.696,
+			22.679, 16.277, 18.738, 20.271, 20.967, 19.157, 20.338,
+		},
+	}
+	expectedMethodResults map[string][]float64 = map[string][]float64{
+		"Mean":              {29.044091, 18.2453333333333},
+		"StandardDeviation": {8.06420820019572, 2.56887224932135},
+		// Population kurtosis
+		"Kurtosis": {0.14431032604193028, -0.8979764294956452},
+		"Variance": {65.0314538961039, 6.59910463333333},
+		// Population skewness
+		"Skewness":  {-0.6233147473136348, -0.2757248239748126},
+		"NumValues": {22, 21},
+		"Min":       {10.68, 13.691},
+		"Max":       {41.08, 22.679},
+	}
+)
+
+func TestStats(t *testing.T) {
+	for i, set := range datasets {
+		s := &Stats{}
+		for _, n := range set {
+			s.Push(n)
+		}
+		for method, values := range expectedMethodResults {
+			t.Run(fmt.Sprintf("%s for set %d", method, i), func(t *testing.T) {
+				m := reflect.ValueOf(s).MethodByName(method).Call([]reflect.Value{})
+				// Round to three decimal places
+				got := math.Round(m[0].Float()*1000) / 1000
+				expected := math.Round(values[i]*1000) / 1000
+				if got != expected {
+					t.Errorf("Method %s failure: \n"+
+						"\tOn set: %d\n"+
+						"\tExpected: %f\n"+
+						"\tGot: %f\n",
+						method, i, expected, got)
+				}
+			})
+		}
+	}
+
+}