269 lines
7.1 KiB
Markdown
269 lines
7.1 KiB
Markdown
# Speed up writing Go test ASAP
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Imagine your project currently have 0% unit test code coverage.
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And your boss keep pushing it to 80% or even 90%?
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What do you do?
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Give up?
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What if I tell you there is a way?
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Not entirely cheating but ... you know, there is always trade off.
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If your purpose is to test carefully all path, check if all return is correctly.
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Sadly this post is not for you, I guess.
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If you only want good number on test coverage, with minimum effort as possible, I hope this will show you some idea you can use :)
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In my opinion, unit test is not that important (like must must have).
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It's just make sure your code is running excatly as you intent it to be.
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If you don't think about edge case before, unit test won't help you.
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## First, rewrite the impossible (to test) out
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When I learn programming, I encounter very interesting idea, which become mainly my mindset when I dev later.
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I don't recall it clearly, kinda like: "Don't just fix bugs, rewrite it so that kind of bugs will not appear again".
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So in our context, there is some thing we hardly or can not write test in Go.
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My suggestion is don't use that thing.
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In my experience, I can list a few here:
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- Read config each time call func (`viper.Get...`). You can and you should init all config when project starts.
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- Not use Dependency Injection (DI). There are too many posts in Internet tell you how to do DI properly.
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- Use global var (Except global var `Err...`). You should move all global var to fields inside some struct.
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## Let the fun (writing test) begin
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If you code Go long enough, you know table driven tests and how is that so useful.
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You set up test data, then you test.
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Somewhere in the future, you change the func, then you need to update test data, then you good!
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In simple case, your func only have 2 or 3 inputs so table drive tests is still looking good.
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But real world is ugly (maybe not, idk I'm just too young in this industry). Your func can have 5 or 10 inputs, also your func call many third party services.
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Imagine having below func to upload image:
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```go
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type service struct {
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db DB
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redis Redis
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minio MinIO
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logService LogService
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verifyService VerifyService
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}
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func (s *service) Upload(ctx context.Context, req Request) error {
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// I simplify by omitting the response, only care error for now
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if err := s.verifyService.Verify(req); err != nil {
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return err
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}
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if err := s.minio.Put(req); err != nil {
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return err
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}
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if err := s.redis.Set(req); err != nil {
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return err
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}
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if err := s.db.Save(req); err != nil {
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return err
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}
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if err := s.logService.Save(req); err != nil {
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return err
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}
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return nil
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}
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```
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With table driven test and thanks to [stretchr/testify](https://github.com/stretchr/testify), I usually write like this:
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```go
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type ServiceSuite struct {
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suite.Suite
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db DBMock
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redis RedisMock
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minio MinIOMock
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logService LogServiceMock
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verifyService VerifyServiceMock
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s service
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}
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func (s *ServiceSuite) SetupTest() {
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// Init mock
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// Init service
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}
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func (s *ServiceSuite) TestUpload() {
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tests := []struct{
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name string
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req Request
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verifyErr error
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minioErr error
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redisErr error
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dbErr error
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logErr error
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wantErr error
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}{
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{
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// Init test case
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}
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}
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for _, tc := range tests {
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s.Run(tc.name, func(){
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// Mock all error depends on test case
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if tc.verifyErr != nil {
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s.verifyService.MockVerify().Return(tc.verifyErr)
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}
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// ...
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gotErr := s.service.Upload(tc.req)
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s.Equal(wantErr, gotErr)
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})
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}
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}
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```
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Looks good right?
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Be careful with this.
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It can go from 0 to 100 ugly real quick.
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What if req is a struct with many fields?
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So in each test case you need to set up req.
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They are almost the same, but with some error case you must alter req.
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It's easy to be init with wrong value here (typing maybe ?).
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Also all req looks similiar, kinda duplicated.
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```go
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tests := []struct{
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name string
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req Request
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verifyErr error
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minioErr error
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redisErr error
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dbErr error
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logErr error
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wantErr error
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}{
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{
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req: Request {
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a: "a",
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b: {
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c: "c",
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d: {
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"e": e
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}
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}
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}
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// Other fieles
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},
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{
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req: Request {
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a: "a",
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b: {
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c: "c",
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d: {
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"e": e
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}
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}
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}
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// Other fieles
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},
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{
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req: Request {
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a: "a",
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b: {
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c: "c",
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d: {
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"e": e
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}
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}
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}
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// Other fieles
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}
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}
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```
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What if dependencies of service keep growing?
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More mock error to test data of course.
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```go
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tests := []struct{
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name string
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req Request
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verifyErr error
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minioErr error
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redisErr error
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dbErr error
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logErr error
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wantErr error
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// Murr error
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aErr error
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bErr error
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cErr error
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// ...
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}{
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{
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// Init test case
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}
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}
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```
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The test file keep growing longer and longer until I feel sick about it.
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See [tektoncd/pipeline unit test](https://github.com/tektoncd/pipeline/blob/main/pkg/pod/pod_test.go) to get a feeling about this.
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When I see it, `TestPodBuild` has almost 2000 lines.
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The solution I propose here is simple (absolutely not perfect, but good with my usecase) thanks to **stretchr/testify**.
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I init all **default** action on **success** case.
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Then I **alter** request or mock error for unit test to hit on other case.
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Remember if unit test is hit, code coverate is surely increaesed, and that my **goal**.
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```go
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// Init ServiceSuite as above
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func (s *ServiceSuite) TestUpload() {
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// Init success request
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req := Request{
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// ...
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}
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// Init success action
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s.verifyService.MockVerify().Return(nil)
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// ...
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gotErr := s.service.Upload(tc.req)
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s.NoError(gotErr)
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s.Run("failed", func(){
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// Alter failed request from default
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req := Request{
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// ...
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}
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gotErr := s.service.Upload(tc.req)
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s.Error(gotErr)
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})
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s.Run("another failed", func(){
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// Alter verify return
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s.verifyService.MockVerify().Return(someErr)
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gotErr := s.service.Upload(tc.req)
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s.Error(gotErr)
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})
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// ...
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}
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```
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If you think this is not quick enough, just **ignore** the response.
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You only need to check error or not if you want code coverage only.
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So if request change fields or more dependencies, I need to update success case, and maybe add corresponding error case if need.
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Same idea but still with table, you can find here [Functional table-driven tests in Go - Fatih Arslan](https://arslan.io/2022/12/04/functional-table-driven-tests-in-go/).
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