test: add test for addDeviceToBridge

add test for addDeviceToBridge in three case
1. addDeviceToBridge successful
2. fail cause no more available bridge slot
3. fail cause state.bridge == 0

Signed-off-by: Ace-Tang <aceapril@126.com>

virtcontainers/qemu.go

@@ -768,7 +768,7 @@ func (q *qemu) addDeviceToBridge(ID string) (string, types.PCIBridge, error) {
 		}
 	}
 
-	return "", types.PCIBridge{}, err
+	return "", types.PCIBridge{}, fmt.Errorf("no more bridge slots available")
 }
 
 func (q *qemu) removeDeviceFromBridge(ID string) error {

virtcontainers/qemu_test.go

@@ -7,6 +7,7 @@ package virtcontainers
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -443,3 +444,41 @@ func TestQemuGrpc(t *testing.T) {
 
 	assert.True(q.id == q2.id)
 }
+
+func TestQemuAddDeviceToBridge(t *testing.T) {
+	assert := assert.New(t)
+
+	config := newQemuConfig()
+	config.DefaultBridges = defaultBridges
+
+	// addDeviceToBridge successfully
+	config.HypervisorMachineType = QemuPC
+	q := &qemu{
+		config: config,
+		arch:   newQemuArch(config),
+	}
+
+	q.state.Bridges = q.arch.bridges(q.config.DefaultBridges)
+	// get pciBridgeMaxCapacity value from virtcontainers/types/pci.go
+	const pciBridgeMaxCapacity = 30
+	for i := uint32(1); i <= pciBridgeMaxCapacity; i++ {
+		_, _, err := q.addDeviceToBridge(fmt.Sprintf("qemu-bridge-%d", i))
+		assert.Nil(err)
+	}
+
+	// fail to add device to bridge cause no more available bridge slot
+	_, _, err := q.addDeviceToBridge("qemu-bridge-31")
+	exceptErr := errors.New("no more bridge slots available")
+	assert.Equal(exceptErr, err)
+
+	// addDeviceToBridge fails cause q.state.Bridges == 0
+	config.HypervisorMachineType = QemuPCLite
+	q = &qemu{
+		config: config,
+		arch:   newQemuArch(config),
+	}
+	q.state.Bridges = q.arch.bridges(q.config.DefaultBridges)
+	_, _, err = q.addDeviceToBridge("qemu-bridge")
+	exceptErr = errors.New("failed to get available address from bridges")
+	assert.Equal(exceptErr, err)
+}