Testing in Go. Why and what is testing. Test pyramid, test types. Specifics on testing with Go.

1. TestinginGo
JaapGroeneveld-jGroeneveld.de

2. Agenda
Whydowetest
Typesoftests
Testdrivendevelopment
TestinginGo
2

3. Whydowetest
Savetime
Confidentinyourchanges
Fasterfeedback
Increasequality
Preventregressions
Communicateanddocument
=>makeyourselfhappier
3

4. Typesoftests
UnitTests(fast)
IntegrationTests
End-to-EndTests(comprehensive)
SmokeTests
ConsumerDrivenContractTests
...
4

5. UnitTests
Focusonsmallparts
Reallyfast
Extensivetestcases
Runbydeveloper
Example:Sum(a,b)
https://martinfowler.com/bliki/UnitTest.html 5

6. Integrationtests
Dounitsworkcorrectlytogether?
Lessextensivetestcases
Runbydeveloper
Example:Webhandler->logic->DB.
6

7. UnitTestvsintegrationtests
https://martinfowler.com/bliki/UnitTest.html 7

8. End-To-Endtests
Fullstacktestagainstrealsystem
Externalboundariesmightbemocked(e.g.
WireMock)
Slow
RunbyCIsystem
Dependingonthesystem,youmightnot
needthem.
https://www.guru99.com/end-to-end-testing.html 8

9. TestPyramid
9

10. Testdrivendevelopment
Red,Green,Refactor
Onlyrefactorwhengreen
Benefits
Nountestedcode
Confidentrefactoring
Betterdesign(...othertalk)
Learngowithtests
10

11. 11

12. GoTestBasics

13. Agenda
GeneralTesting
Whattotest
Subtests
Tabletests
Mocks
13

14. Go'stestfunctionalities
go test ./... picksuptestsdefinedin X_test.go files
Xisusuallythenameofthecodefile sum.go => sum_test.go
Testshavethesignature func TestX(t *testing.T)
Xisusuallythenameoftheunit(functionorstruct)
Testfailuresarereportedwith t.Error and t.Fatal
Youcanalsorunbenchmarkswith func Benchmark*(b *testing.B) appendix
YoucanalsorundefineExamplesfordocumentation func Example*() appendix
14

15. Asimpletest
func Sum(elements []int) int
func TestSum(t *testing.T) {
input := []int{1, 2, 3}
expected := 6
actual := Sum(input)
if actual != expected {
t.Errorf("expected %v but was %v", expected, actual)
}
}
15

16. CleanCode-Tests
Oneassertpertest.
Readable.
Fast.
Independent.
Repeatable.
(...othertalk)
16

17. 1.Arrange
2.Act
3.Assert
17

18. Acleanersimpletest
func TestSum(t *testing.T) {
// Arrange
input := []int{1, 2, 3}
expected := 6
// Act
actual := Sum(input)
// Assert
if actual != expected {
t.Errorf("expected %v but was %v", expected, actual)
}
}
18

19. Yourturn!
Startanewproject,writesimpletestandletthetestguideyoutoimplementthe
method.
19

20. TestFrameworks
gotest
expected := "bar"
actual, err := Foo()
if err != nil {
t.Fatalf("got error %v", err)
}
if expected != actual {
t.Errorf("expected %v but got %v", expected, actual)
}
testify
actual, err := Foo()
require.Nil(t, err)
assert.Equal(t, "bar", actual)
20

21. TestFrameworks
Comparisonofgotestingframeworks(Testify,gocheck,gopwt,Ginkgo...)
https://github.com/bmuschko/go-testing-frameworks
21

22. Whattotest
Commoncase(Happypath)
Edgecases
Errorcases
22

23. Subtests
Letyouorganizeyourteststocommunicatetheintentionmoreclearly
func TestSum(t *testing.T) {
t.Run("returns the summed up elements", func(t *testing.T) {
// []...]
})
t.Run("returns zero for empty array", func(t *testing.T) {
// []...]
})
}
23

24. Tablebasedtests
Inaperfectworld,functionsjustrelyoninputandoutput.Thisiseasytotest.
func TestSum(t *testing.T) {
testCases := []struct {
Name string
Input []int
Expected int
}{
{
Name: "returns the summed up elements",
Input: []int{1, 2, 3},
Expected: 6,
},
{
Name: "returns zero for empty array",
Input: []int{}.
Expected: 0,
},
}
for _, tc := range testCases {
t.Run(tc.Name, func(t *testing.T) {
assert.Equal(t, tc.Expected, Sum(tc.input))
})
}
} 24

25. generateNodeName
CodeReview
25

26. TestDoubles
26

27. Testdoubles
Fakes:Workingimplementation
Stubs:Holdpredefineddata
Mocks:Registercallstheyreceiveanddonothing
Spies:Registercallstorealobjects
27

28. Whyusedoubles
Toreallytest"units"andnotthedependencies
Performance-Databases,Network...
Collaboration-Implementcodeagainstdependenciesthatdonotexist,yet.
28

29. SimpleMocks:Code
Wehaveafunction SendMail thatformatsamessageandusesthe MailSender to
senditout.
Sendingmailsisslowandwejustwanttoknowthatitwouldhappenwiththecorrect
message.
func SendMail(sender MailSender, recipient string) {
sender.Send("Good morning, " + recipient)
}
type MailSender interface {
Send(message string)
}
29

30. SimpleMocks:Test
func TestSendMail(t *testing.T) {
calledWith := ""
sender := MockMailSender{
SendFunc: func(message string) {
calledWith = message
},
}
SendMail(sender, "Tyrion")
if calledWith != "Good morning, Tyrion" {
t.Errorf("Was called with %q", calledWith)
}
}
30

31. SimpleMocks:Mock
type MockMailSender struct {
SendFunc func(message string)
}
func (s MockMailSender) Send(message string) {
s.SendFunc(message)
}
31

32. MockingFrameworks
gomockusescodegenerationtoprovidemocks
mockgen -source=mail_sender.go
func TestFoo(t *testing.T) {
ctrl := gomock.NewController(t)
defer ctrl.Finish()
sender := NewMockMailSender(ctrl)
sender.
EXPECT().
Send("Good morning, Tyrion")
SendMail(sender, "Tyrion")
}
32

33. 33

34. Randomthings
34

35. Writinghelpers
func equals(t *testing.T, a string, b string) {
t.Helper()
if a != b {
t.Errorf("%q is not %q", a, b)
}
}
35

36. httptest.NewRecorder
func TestGetPlayers(t *testing.T) {
playerStore := &StubPlayerStore{map[string]int{
"Pepper": 20,
}}
server := PlayerServer{playerStore}
request, _ := http.NewRequest(http.MethodGet, "/scores/pepper", nil)
response := httptest.NewRecorder()
server.ServeHTTP(response, request)
assert.Equal(t, http.StatusOK, response.Code)
assert.Equal(t, "20", response.Body.String())
}
Useashttp.ResponseWritertotestyourownhandlers
36

37. httptest.NewServer
server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(http.StatusOK)
}))
defer server.Close()
// pass server.URL somewhere
Greattofakerealapisforintegrationtesting.
AlsoseeWireMockmockservertoconfigurearealserverifyouwanttotestthe
infrastructure.
37

38. TestingJSONresponses(schema)
func TestJSON(t *testing.T) {
reader := getJSONResponse()
err := schema.MatchJSON(
schema.Map{
"id": schema.IsInteger,
"name": "Max Mustermann",
"age": 42,
"height": schema.IsFloat,
"footsize": schema.IsPresent,
"address": schema.Map{
"street": schema.IsString,
"zip": schema.IsString,
},
"tags": schema.ArrayIncluding("red"),
},
reader,
)
}
https://github.com/jgroeneveld/schema 38

39. Examples
package stringutil_test
import (
"fmt"
"github.com/golang/example/stringutil"
)
func ExampleReverse() {
fmt.Println(stringutil.Reverse("hello"))
// Output: olleh
}
Examplesrunliketests,soweknow
theyarecorrect,andgenerate
documentation.
39

40. Benchmarks
func BenchmarkFib10(b *testing.B) {
// run the Fib function b.N times
for n := 0; n < b.N; n++ {
Fib(10)
}
}
% go test -bench=.
PASS
BenchmarkFib10 5000000 509 ns/op
ok github.com/davecheney/fib 3.084s
40

41. Setup/Teardown
func TestFoo() {
var teardown = setup()
defer teardown()
// ...
}
func setup() func() {
fmt.Println("this runs before test")
return func() {
fmt.Println("this runs after test")
}
}
Greatifyouneedtodosomethingbeforetestsrunandalsocleanupafterwards
e.g.disablelogging,prepare&cleandatabase,set/resetENV.
41

42. Globalhooks
Youcanplacea func init() inthepackage_testtorunbeforethetestsrun.
Better:InGo1.14wehavetheTestMain
func TestMain(m *testing.M) {
// call flag.Parse() here if TestMain uses flags
fmt.Println("this runs before test")
exitCode := m.Run()
fmt.Println("this runs after test")
os.Exit(exitCode)
}
42

43. quick.Checkforpropertytesting
Usethequickpackagetotestpropertieswithrandominputs
func TestPropertiesOfConversion(t *testing.T) {
t.Run("Conversion to roman and back to arabic yields initial input", func(t *testing.T) {
assertion := func(arabic int) bool {
roman := ConvertToRoman(arabic)
fromRoman := ConvertToArabic(roman)
return fromRoman == arabic
}
if err := quick.Check(assertion, nil); err != nil {
t.Error("failed checks", err)
}
})
}
43