mockpkg uses mockery to generate mocks
for a package as if the package were an interface.
Usage: mockpkg [options] <package> [<func1> <func2> ...]
-outfile string
file to write mocks to; if empty output to stdout
-overwrite
overwrite the destination file if it exists
-tags string
space-separated list of additional build tags to use
Suppose you number your hosts using suffixes in their short hostnames (e.g.,
node01.example.com), and have a package to return the node number:
package hostnum
var (
errNoNumber = errors.New("no number in hostname")
)
func FromHostname() (int, error) {
hn, err := os.Hostname()
if err != nil {
return 0, err
}
short := strings.Split(hn, ".")[0]
re := regexp.MustCompile(`.+(\d+)$`)
m := re.FindStringSubmatch(short)
if len(m) < 1 {
return 0, errNoNumber
}
return strconv.Atoi(m[1])
}You'd like to write unit tests for this package, but since it uses
os.Hostname, you'd have to run it on a bunch of hosts to effectively test all
the cases.
By making the hostname function a non-exported variable in the package, you can inject it from tests:
package hostnum
var (
errNoNumber = errors.New("no number in hostname")
hostnameFn = os.Hostname
)
func FromHostname() (int, error) {
hn, err := hostnameFn()
if err != nil {
return 0, err
}
short := strings.Split(hn, ".")[0]
re := regexp.MustCompile(`.+(\d+)$`)
m := re.FindStringSubmatch(short)
if len(m) < 1 {
return 0, errNoNumber
}
return strconv.Atoi(m[1])
}mockpkg can be used to generate a mock for the hostname function:
$ mockpkg -outfile mocks/hostname.go os HostnameAnd the resulting mock can be injected for tests:
package hostnum
import (
"testing"
"example.com/hostnum/mocks"
"github.com/stretchr/testify/assert"
)
func TestFromHostname(t *testing.T) {
mockOS := &mocks.Os{}
hostnameFn = mockOS.Hostname
t.Run("host 1", func(t *testing.T) {
mockOS.On("Hostname").Return("host01.example.com", nil).Once()
n, err := FromHostname()
assert.NoError(t, err)
assert.Equal(t, 1, n)
})
}mockpkgusesmockeryto perform the actual mock generation.- The generated mocks
use
testify/mock.