Adding test for happy path retrieving max power.

go.sum

@@ -1,5 +1,6 @@
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fatih/color v1.7.0 h1:DkWD4oS2D8LGGgTQ6IvwJJXSL5Vp2ffcQg58nFV38Ys=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=

rapl-daemon/util_test.go

@@ -1,10 +1,18 @@
 package main
 
-import "testing"
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
 
 // TODO(rdelvalle): Add more thourough testing. Generate mock files
 // that mimic the powercap subsystem and create test to operate on it.
-func TestCap(t *testing.T) {
+func TestCapNode(t *testing.T) {
 
 	err := capNode("/sys/devices/virtual/powercap/intel-rapl", 95)
 
@@ -12,3 +20,23 @@ func TestCap(t *testing.T) {
 		t.Fail()
 	}
 }
+
+func TestMaxPower(t *testing.T) {
+	const maxWattage uint64 = 1500000
+
+	tmpfile, err := ioutil.TempFile("", maxPowerFileShortWindow)
+	assert.NoError(t, err)
+
+	defer os.Remove(tmpfile.Name())
+
+	fmt.Println(tmpfile.Name())
+	_, err = tmpfile.Write([]byte(strconv.FormatUint(maxWattage, 10)))
+	assert.NoError(t, err)
+
+	maxWatts, err := maxPower(tmpfile.Name())
+	assert.NoError(t, err)
+	assert.Equal(t, maxWattage, maxWatts)
+
+	err = tmpfile.Close()
+	assert.NoError(t, err)
+}