2 files changed, 118 insertions, 2 deletions
diff --git a/internal/failover/monitor.go b/internal/failover/monitor.go
index 5b44ee6..6f3e551 100644
--- a/internal/failover/monitor.go
+++ b/internal/failover/monitor.go
@@ -8,6 +8,11 @@ import (
 	"github.com/eduvpn/eduvpn-common/internal/log"
 )
 
+type sender interface {
+	Read(deadline time.Time) error
+	Send(seq int) error
+}
+
 // The DroppedConMon is a connection monitor that checks for an increase in rx bytes in certain intervals
 type DroppedConMon struct {
 	// pInterval means how the interval in which to send pings
@@ -17,6 +22,9 @@ type DroppedConMon struct {
 	// The function that reads Rx bytes
 	// If this function returns an error, the monitor exits
 	readRxBytes func() (int64, error)
+	// newPinger creates a new pinger
+	// This gets used in the tests to mock the Ping sender interface
+	newPinger func(gateway string, mtu int) (sender, error)
 }
 
 // NewDroppedMonitor creates a new failover monitor
@@ -24,7 +32,9 @@ type DroppedConMon struct {
 // `pDropped` is how many pings we need to send before we deem it is dropped
 // `readRxBytes` is a function that gets the rx bytes from the client
 func NewDroppedMonitor(pingInterval time.Duration, pDropped int, readRxBytes func() (int64, error)) *DroppedConMon {
-	return &DroppedConMon{pInterval: pingInterval, pDropped: pDropped, readRxBytes: readRxBytes}
+	return &DroppedConMon{pInterval: pingInterval, pDropped: pDropped, readRxBytes: readRxBytes, newPinger: func(gateway string, mtu int) (sender, error) {
+		return NewPinger(gateway, mtu)
+	}}
 }
 
 // Dropped checks whether or not the connection is 'dropped'
@@ -47,7 +57,7 @@ func (m *DroppedConMon) Start(ctx context.Context, gateway string, mtuSize int)
 	}
 
 	// Create a ping struct with our mtu size
-	p, err := NewPinger(gateway, mtuSize)
+	p, err := m.newPinger(gateway, mtuSize)
 	if err != nil {
 		return false, err
 	}
diff --git a/internal/failover/monitor_test.go b/internal/failover/monitor_test.go
new file mode 100644
index 0000000..87fb3cd
--- /dev/null
+++ b/internal/failover/monitor_test.go
@@ -0,0 +1,106 @@
+package failover
+
+import (
+	"context"
+	"errors"
+	"io"
+	"testing"
+	"time"
+
+	"github.com/eduvpn/eduvpn-common/internal/test"
+)
+
+// mockedPinger is a ping sender that always returns nil for sending
+// but returns EOF for reading
+type mockedPinger struct{}
+
+func (mp *mockedPinger) Read(_ time.Time) error {
+	return io.EOF
+}
+
+func (mp *mockedPinger) Send(_ int) error {
+	return nil
+}
+
+func TestMonitor(t *testing.T) {
+	cases := []struct {
+		interval        time.Duration
+		pDropped        int
+		readRxBytes     func() (int64, error)
+		gateway         string
+		mtuSize         int
+		disableDefaults bool
+		mockedPinger    func(gateway string, mtu int) (sender, error)
+		wantDropped     bool
+		wantErr         string
+	}{
+		{
+			mtuSize:     1,
+			wantDropped: false,
+			wantErr:     "invalid MTU size given, MTU has to be at least: 28 bytes",
+		},
+		{
+			readRxBytes: func() (int64, error) {
+				return 0, errors.New("error test")
+			},
+			wantDropped: false,
+			wantErr:     "error test",
+		},
+		// default case, not dropped
+		{},
+		// readRxBytes always returns 0
+		// still we do not want a drop because we get a pong from 127.0.0.1
+		{
+			readRxBytes: func() (int64, error) {
+				return 0, nil
+			},
+			wantDropped: false,
+		},
+		// readRxBytes always returns 0
+		// we want dropped as the mock pinger does nothing
+		{
+			readRxBytes: func() (int64, error) {
+				return 0, nil
+			},
+			gateway: "127.0.0.1",
+			mockedPinger: func(_ string, _ int) (sender, error) {
+				return &mockedPinger{}, nil
+			},
+			wantDropped: true,
+		},
+	}
+
+	for _, c := range cases {
+		var counter int64
+		// some defaults
+		if c.interval == 0 {
+			c.interval = 2 * time.Second
+		}
+		if c.pDropped == 0 {
+			c.pDropped = 5
+		}
+		if c.gateway == "" {
+			c.gateway = "127.0.0.1"
+		}
+		if c.mtuSize == 0 {
+			c.mtuSize = 28
+		}
+		if c.readRxBytes == nil {
+			c.readRxBytes = func() (int64, error) {
+				defer func() {
+					counter++
+				}()
+				return counter, nil
+			}
+		}
+		dcm := NewDroppedMonitor(c.interval, c.pDropped, c.readRxBytes)
+		if c.mockedPinger != nil {
+			dcm.newPinger = c.mockedPinger
+		}
+		dropped, err := dcm.Start(context.Background(), c.gateway, c.mtuSize)
+		if dropped != c.wantDropped {
+			t.Fatalf("dropped is not equal to want dropped, got: %v, want: %v", dropped, c.wantDropped)
+		}
+		test.AssertError(t, err, c.wantErr)
+	}
+}