diff --git a/les/balance_test.go b/les/balance_test.go
new file mode 100644
index 000000000..b571c2cc5
--- /dev/null
+++ b/les/balance_test.go
@@ -0,0 +1,260 @@
+// Copyright 2019 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library 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 Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package les
+
+import (
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+)
+
+func TestSetBalance(t *testing.T) {
+	var clock = &mclock.Simulated{}
+	var inputs = []struct {
+		pos uint64
+		neg uint64
+	}{
+		{1000, 0},
+		{0, 1000},
+		{1000, 1000},
+	}
+
+	tracker := balanceTracker{}
+	tracker.init(clock, 1000)
+	defer tracker.stop(clock.Now())
+
+	for _, i := range inputs {
+		tracker.setBalance(i.pos, i.neg)
+		pos, neg := tracker.getBalance(clock.Now())
+		if pos != i.pos {
+			t.Fatalf("Positive balance mismatch, want %v, got %v", i.pos, pos)
+		}
+		if neg != i.neg {
+			t.Fatalf("Negative balance mismatch, want %v, got %v", i.neg, neg)
+		}
+	}
+}
+
+func TestBalanceTimeCost(t *testing.T) {
+	var (
+		clock   = &mclock.Simulated{}
+		tracker = balanceTracker{}
+	)
+	tracker.init(clock, 1000)
+	defer tracker.stop(clock.Now())
+	tracker.setFactors(false, 1, 1)
+	tracker.setFactors(true, 1, 1)
+
+	tracker.setBalance(uint64(time.Minute), 0) // 1 minute time allowance
+
+	var inputs = []struct {
+		runTime time.Duration
+		expPos  uint64
+		expNeg  uint64
+	}{
+		{time.Second, uint64(time.Second * 59), 0},
+		{0, uint64(time.Second * 59), 0},
+		{time.Second * 59, 0, 0},
+		{time.Second, 0, uint64(time.Second)},
+	}
+	for _, i := range inputs {
+		clock.Run(i.runTime)
+		if pos, _ := tracker.getBalance(clock.Now()); pos != i.expPos {
+			t.Fatalf("Positive balance mismatch, want %v, got %v", i.expPos, pos)
+		}
+		if _, neg := tracker.getBalance(clock.Now()); neg != i.expNeg {
+			t.Fatalf("Negative balance mismatch, want %v, got %v", i.expNeg, neg)
+		}
+	}
+
+	tracker.setBalance(uint64(time.Minute), 0) // Refill 1 minute time allowance
+	for _, i := range inputs {
+		clock.Run(i.runTime)
+		if pos, _ := tracker.getBalance(clock.Now()); pos != i.expPos {
+			t.Fatalf("Positive balance mismatch, want %v, got %v", i.expPos, pos)
+		}
+		if _, neg := tracker.getBalance(clock.Now()); neg != i.expNeg {
+			t.Fatalf("Negative balance mismatch, want %v, got %v", i.expNeg, neg)
+		}
+	}
+}
+
+func TestBalanceReqCost(t *testing.T) {
+	var (
+		clock   = &mclock.Simulated{}
+		tracker = balanceTracker{}
+	)
+	tracker.init(clock, 1000)
+	defer tracker.stop(clock.Now())
+	tracker.setFactors(false, 1, 1)
+	tracker.setFactors(true, 1, 1)
+
+	tracker.setBalance(uint64(time.Minute), 0) // 1 minute time serving time allowance
+	var inputs = []struct {
+		reqCost uint64
+		expPos  uint64
+		expNeg  uint64
+	}{
+		{uint64(time.Second), uint64(time.Second * 59), 0},
+		{0, uint64(time.Second * 59), 0},
+		{uint64(time.Second * 59), 0, 0},
+		{uint64(time.Second), 0, uint64(time.Second)},
+	}
+	for _, i := range inputs {
+		tracker.requestCost(i.reqCost)
+		if pos, _ := tracker.getBalance(clock.Now()); pos != i.expPos {
+			t.Fatalf("Positive balance mismatch, want %v, got %v", i.expPos, pos)
+		}
+		if _, neg := tracker.getBalance(clock.Now()); neg != i.expNeg {
+			t.Fatalf("Negative balance mismatch, want %v, got %v", i.expNeg, neg)
+		}
+	}
+}
+
+func TestBalanceToPriority(t *testing.T) {
+	var (
+		clock   = &mclock.Simulated{}
+		tracker = balanceTracker{}
+	)
+	tracker.init(clock, 1000) // cap = 1000
+	defer tracker.stop(clock.Now())
+	tracker.setFactors(false, 1, 1)
+	tracker.setFactors(true, 1, 1)
+
+	var inputs = []struct {
+		pos      uint64
+		neg      uint64
+		priority int64
+	}{
+		{1000, 0, ^int64(1)},
+		{2000, 0, ^int64(2)}, // Higher balance, lower priority value
+		{0, 0, 0},
+		{0, 1000, 1000},
+	}
+	for _, i := range inputs {
+		tracker.setBalance(i.pos, i.neg)
+		priority := tracker.getPriority(clock.Now())
+		if priority != i.priority {
+			t.Fatalf("Priority mismatch, want %v, got %v", i.priority, priority)
+		}
+	}
+}
+
+func TestEstimatedPriority(t *testing.T) {
+	var (
+		clock   = &mclock.Simulated{}
+		tracker = balanceTracker{}
+	)
+	tracker.init(clock, 1000000000) // cap = 1000,000,000
+	defer tracker.stop(clock.Now())
+	tracker.setFactors(false, 1, 1)
+	tracker.setFactors(true, 1, 1)
+
+	tracker.setBalance(uint64(time.Minute), 0)
+	var inputs = []struct {
+		runTime    time.Duration // time cost
+		futureTime time.Duration // diff of future time
+		reqCost    uint64        // single request cost
+		priority   int64         // expected estimated priority
+	}{
+		{time.Second, time.Second, 0, ^int64(58)},
+		{0, time.Second, 0, ^int64(58)},
+
+		// 2 seconds time cost, 1 second estimated time cost, 10^9 request cost,
+		// 10^9 estimated request cost per second.
+		{time.Second, time.Second, 1000000000, ^int64(55)},
+
+		// 3 seconds time cost, 3 second estimated time cost, 10^9*2 request cost,
+		// 4*10^9 estimated request cost.
+		{time.Second, 3 * time.Second, 1000000000, ^int64(48)},
+
+		// All positive balance is used up
+		{time.Second * 55, 0, 0, 0},
+
+		// 1 minute estimated time cost, 4/58 * 10^9 estimated request cost per sec.
+		{0, time.Minute, 0, int64(time.Minute) + int64(time.Second)*120/29},
+	}
+	for _, i := range inputs {
+		clock.Run(i.runTime)
+		tracker.requestCost(i.reqCost)
+		priority := tracker.estimatedPriority(clock.Now()+mclock.AbsTime(i.futureTime), true)
+		if priority != i.priority {
+			t.Fatalf("Estimated priority mismatch, want %v, got %v", i.priority, priority)
+		}
+	}
+}
+
+func TestCallbackChecking(t *testing.T) {
+	var (
+		clock   = &mclock.Simulated{}
+		tracker = balanceTracker{}
+	)
+	tracker.init(clock, 1000000) // cap = 1000,000
+	defer tracker.stop(clock.Now())
+	tracker.setFactors(false, 1, 1)
+	tracker.setFactors(true, 1, 1)
+
+	var inputs = []struct {
+		priority int64
+		expDiff  time.Duration
+	}{
+		{^int64(500), time.Millisecond * 500},
+		{0, time.Second},
+		{int64(time.Second), 2 * time.Second},
+	}
+	tracker.setBalance(uint64(time.Second), 0)
+	for _, i := range inputs {
+		diff, _ := tracker.timeUntil(i.priority)
+		if diff != i.expDiff {
+			t.Fatalf("Time difference mismatch, want %v, got %v", i.expDiff, diff)
+		}
+	}
+}
+
+func TestCallback(t *testing.T) {
+	var (
+		clock   = &mclock.Simulated{}
+		tracker = balanceTracker{}
+	)
+	tracker.init(clock, 1000) // cap = 1000
+	defer tracker.stop(clock.Now())
+	tracker.setFactors(false, 1, 1)
+	tracker.setFactors(true, 1, 1)
+
+	callCh := make(chan struct{}, 1)
+	tracker.setBalance(uint64(time.Minute), 0)
+	tracker.addCallback(balanceCallbackZero, 0, func() { callCh <- struct{}{} })
+
+	clock.Run(time.Minute)
+	select {
+	case <-callCh:
+	case <-time.NewTimer(time.Second).C:
+		t.Fatalf("Callback hasn't been called yet")
+	}
+
+	tracker.setBalance(uint64(time.Minute), 0)
+	tracker.addCallback(balanceCallbackZero, 0, func() { callCh <- struct{}{} })
+	tracker.removeCallback(balanceCallbackZero)
+
+	clock.Run(time.Minute)
+	select {
+	case <-callCh:
+		t.Fatalf("Callback shouldn't be called")
+	case <-time.NewTimer(time.Millisecond * 100).C:
+	}
+}