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Update UT Examples #4

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59 changes: 43 additions & 16 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -494,25 +494,56 @@ Use function variable when you need to test a package level function:
func GetIPNetDeviceByName(ifaceName string) (v4IPNet *net.IPNet, v6IPNet *net.IPNet, link *net.Interface, err error) {
link, err = net.InterfaceByName(ifaceName) // External dependency makes it hard to test directly.
...
addrList, err := link.Addrs() // Calling original method of link makes it hard to test with custom output.
...
}

// Declare a package level function variable.
var interfaceByName = net.InterfaceByName
var(
interfaceByName = net.InterfaceByName
netInterfaceAddrs = (*net.Interface).Addrs
)

func GetIPNetDeviceByName(ifaceName string) (v4IPNet *net.IPNet, v6IPNet *net.IPNet, link *net.Interface, err error) {
link, err = interfaceByName(ifaceName) // Use the variable for actual call.
// Use the variables for actual call.
link, err = interfaceByName(ifaceName)
...
addrList, err := netInterfaceAddrs(link)
...
}

func mockNetInterfaceByName(testNetInterface *net.Interface, err error) func() {
// Mock the variable for test.
originalNetInterfaceByName := netInterfaceByName
netInterfaceByName = func(name string) (*net.Interface, error) {
return testNetInterface, err
}
return func() {
netInterfaceByName = originalNetInterfaceByName
}
}

func mockNetInterfaceAddrs(testNetInterfaceAddrs []net.Addr, err error) func() {
// Mock the method for test.
originalNetInterfaceAddrs := netInterfaceAddrs
netInterfaceAddrs = func(i *net.Interface) ([]net.Addr, error) {
return testNetInterfaceAddrs, err
}
return func() {
netInterfaceAddrs = originalNetInterfaceAddrs
}
}

func TestGetIPNetDeviceByName(t *testing.T) {
tests := []struct {
name string
interfaceName string
interface *net.Interface
wantV4IPNet *net.IPNet
wantV6IPNet *net.IPNet
wantLink *net.Interface
wantErr error
name string
interfaceName string
interface *net.Interface
interfaceAddrs []net.Addr
wantV4IPNet *net.IPNet
wantV6IPNet *net.IPNet
wantLink *net.Interface
wantErr error
}{
{name: "case 1", ...},
{name: "case 2", ...},
Expand All @@ -521,13 +552,9 @@ func TestGetIPNetDeviceByName(t *testing.T) {

for _, tc := range tests {
t.Run(tc.name, func(t *testing.T) {
// Mock the variable for test.
interfaceByName = func(name string) (*net.Interface, error) {
return tc.interface
}
defer func() {
interfaceByName = net.InterfaceByName
}()
// Set mocks, defer the returned functions for reset.
defer mockNetInterfaceByName(tc.interface, nil)()
defer mockNetInterfaceAddrs(tc.interfaceAddrs, nil)()
gotV4IPNet, gotV6IPNet, gotLink, gotErr := GetIPNetDeviceByName(tc.name)
assert.Equal(t, tc.wantV4IPNet, gotV4IPNet)
assert.Equal(t, tc.wantV6IPNet, gotV6IPNet)
Expand Down