I am having a hard time getting my test for my emitter function which passes results through a channel for a data pipeline. This function will be triggered periodically and will pull records from the database. I compiled an stripped done version for this question the real code would more complex but would follow the same pattern. For testing I mocked the access to the database because I want to test the behavoir of the Emitter function.
I guess code is more than words:
This is the method I want to test:
//EmittRecord pull record from database
func EmittRecord(svc Service, count int) <-chan *Result {
out := make(chan *Result)
go func() {
defer close(out)
for i := 0; i < count; i++ {
r, err := svc.Next()
if err != nil {
out <- &Result{Error: err}
continue
}
out <- &Result{Payload: &Payload{
Field1: r.Field1,
Field2: r.Field2,
}, Error: nil}
}
}()
return out
}
I have a couple of types with an interface:
//Record is a Record from db
type Record struct {
Field1 string
Field2 string
}
//Payload is a record for the data pipeline
type Payload struct {
Field1 string
Field2 string
}
//Result is a type for the data pipeline
type Result struct {
Payload *Payload
Error error
}
//Service is an abstraction to access the database
type Service interface {
Next() (*Record, error)
}
This is my service Mock for testing:
//MockService is a struct to support testing for mocking the database
type MockService struct {
NextMock func() (*Record, error)
}
//Next is an Implementation of the Service interface for the mock
func (m *MockService) Next() (*Record, error) {
if m.NextMock != nil {
return m.NextMock()
}
panic("Please set NextMock!")
}
And finally this is my test method which does not work. It does not hit the done case and das not hit the 1*time.Second
timeout case either ... the test just times out. I guess I am missing something here.
func TestEmitter(t *testing.T) {
tt := []struct {
name string
svc runner.Service
expectedResult runner.Result
}{
{name: "Database returns error",
svc: &runner.MockService{
NextMock: func() (*runner.Record, error) {
return nil, fmt.Errorf("YIKES")
},
},
expectedResult: runner.Result{Payload: nil, Error: fmt.Errorf("RRRR")},
},
{name: "Database returns record",
svc: &runner.MockService{
NextMock: func() (*runner.Record, error) {
return &runner.Record{
Field1: "hello",
Field2: "world",
}, nil
},
},
},
}
for _, tc := range tt {
t.Run(tc.name, func(t *testing.T) {
done := make(chan bool)
defer close(done)
var output <-chan *runner.Result
go func() {
output = runner.EmittRecord(tc.svc, 1)
done <- true
}()
found := <-output
<-done
select {
case <-done:
case <-time.After(1 * time.Second):
panic("timeout")
}
if found.Error.Error() != "Hello" {
t.Errorf("FAIL: %s, expected: %s; but got %s", tc.name, tc.expectedResult.Error.Error(), found.Error.Error())
} else if reflect.DeepEqual(found.Payload, tc.expectedResult.Payload) {
t.Errorf("FAIL: %s, expected: %+v; got %+v", tc.name, tc.expectedResult.Payload, found.Payload)
}
})
}
}
It would be great, if someone could give me an advice what I missing here and maybe some input how to verify the count of the EmittRecord
function right now it is only set to 1
Thanks in advance
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