Unit testing for pcp module.

Added unit tests to test code in def/ module.
Currently, AverageNodePowerHistory(...) assumes that the DRAM power
readings are being monitored. In addition, it also assumes that the
host servers are dual socket machines. However, this assumption might
not always hold true. Thus, added a TODO to fix this.

pcp/victim_test.go

@@ -0,0 +1,50 @@
+// Copyright (C) 2018 spdf
+//
+// This file is part of Elektron.
+//
+// Elektron is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Elektron is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Elektron.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+package pcp
+
+import (
+	"github.com/stretchr/testify/assert"
+	"sort"
+	"testing"
+)
+
+// TestVictimSorter tests whether victim nodes are sorted in the non-increasing
+// order of Watts consumption.
+func TestVictimSorter(t *testing.T) {
+	victims := []Victim{
+		{Watts: 10.0, Host: "host1"},
+		{Watts: 20.0, Host: "host2"},
+		{Watts: 30.0, Host: "host3"},
+		{Watts: 40.0, Host: "host4"},
+	}
+
+	sort.Sort(VictimSorter(victims))
+
+	expectedVictimsOrder := []Victim{
+		{Watts: 40.0, Host: "host4"},
+		{Watts: 30.0, Host: "host3"},
+		{Watts: 20.0, Host: "host2"},
+		{Watts: 10.0, Host: "host1"},
+	}
+
+	for i, v := range expectedVictimsOrder {
+		assert.Equal(t, v.Watts, victims[i].Watts, "failed to sorted victims")
+		assert.Equal(t, v.Host, victims[i].Host, "failed to sorted victims")
+	}
+}