Adding some more coverage for unhappy paths and fixing some values to reflect they are no longer floats.

rapl-daemon/util.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"math"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -65,12 +66,12 @@ func capNode(base string, percentage int) error {
 func maxPower(maxFile string) (uint64, error) {
 	maxPower, err := ioutil.ReadFile(maxFile)
 	if err != nil {
-		return 0.0, err
+		return 0, err
 	}
 
 	maxPoweruW, err := strconv.ParseUint(strings.TrimSpace(string(maxPower)), 10, 64)
 	if err != nil {
-		return 0.0, err
+		return 0, err
 	}
 
 	return maxPoweruW, nil
@@ -78,6 +79,10 @@ func maxPower(maxFile string) (uint64, error) {
 
 // capZone caps a power zone to a specific amount of watts specified by value
 func capZone(limitFile string, value uint64) error {
+	if _, err := os.Stat(limitFile); os.IsNotExist(err) {
+		return err
+	}
+
 	err := ioutil.WriteFile(limitFile, []byte(strconv.FormatUint(value, 10)), 0644)
 	if err != nil {
 		return err

rapl-daemon/util_test.go

@@ -52,6 +52,16 @@ func TestMain(m *testing.M) {
 func TestCapNode(t *testing.T) {
 	err := capNode(raplDir, 95)
 	assert.NoError(t, err)
+
+	t.Run("badPercentage", func(t *testing.T) {
+		err := capNode(raplDir, 1000)
+		assert.Error(t, err)
+	})
+
+	t.Run("zeroPercent", func(t *testing.T) {
+		err := capNode(raplDir, 0)
+		assert.Error(t, err)
+	})
 }
 
 func TestMaxPower(t *testing.T) {
@@ -60,6 +70,11 @@ func TestMaxPower(t *testing.T) {
 	maxWatts, err := maxPower(maxFile)
 	assert.NoError(t, err)
 	assert.Equal(t, maxWattage, maxWatts)
+
+	t.Run("nameDoesNotExist", func(t *testing.T) {
+		_, err := maxPower("madeupname")
+		assert.Error(t, err)
+	})
 }
 
 func TestCapZone(t *testing.T) {
@@ -76,4 +91,9 @@ func TestCapZone(t *testing.T) {
 	newCap, err := strconv.ParseUint(strings.TrimSpace(string(newCapBytes)), 10, 64)
 	assert.NoError(t, err)
 	assert.Equal(t, powercap, newCap)
+
+	t.Run("nameDoesNotExist", func(t *testing.T) {
+		err := capZone("madeupname", powercap)
+		assert.Error(t, err)
+	})
 }