Just list some testing way in Go.
Basically, we use testing
this built-in lib to testing
To start your first test with Go is an easy task.
Example(we would test the following function under directory add
)
package add
func Add(x, y int) int { return x + y }
- create a file contains suffix
_test
, it would be a test file, e.g.add_test.go
- create a function in test file has prefix
Test
, uset *testing.T
as it’s parameter
package add
import "testing"
func TestAdd(t *testing.T) {
if Add(1, 2) != 3 {
t.Errorf("Add(1, 2) should be 3 but: %d", Add(1, 2))
}
}
- type
go test
& execute it in terminal
Ok, now we got a test, if you see the error message then must something wrong about your implementation of Add
p.s. Usually, we won’t use
go test
butgo test ./...
because we would have a lot of package under a project,./...
would find out every sub directory(those can be a go package) & run test
We have func (*testing.T) Run(subTestName string, subTest func(t *testing.T))
this function, we can use it to create a new sub test.
func TestCarFactory(t *testing.T) {
factory := car.NewFactory()
t.Run("Toyota", func(t *testing.T) {
toyota := factory.Build(car.Toyota)
// test toyota
})
t.Run("Mazda", func(t *testing.T) {
mazda := factory.Build(car.Mazda)
// test mazda
})
}
Basically, you can see sub test means we want to reuse the same context for different tests, or like me, just use it represents the test structure.
A practical problem is sometimes we extract a test helper out of the test function.
For example:
func assertNoError(t *testing.T, err error) {
if err != nil {
t.Errorf("assert no error but: %s", err)
}
}
You will find all error say it happened at t.Errorf
that line, but not the error actually happened place!
To solve this problem, you have to add t.Helper()
this function call, according document:
Helper marks the calling function as a test helper function. When printing file and line information, that function will be skipped.
Helper
may be called simultaneously from multiple goroutines.
I recommend https://github.com/stretchr/testify for the assertion, Don’t Reinvent The Wheel! (Something I always violate it)
And https://github.com/gavv/httpexpect is an awesome lib for web API testing.
A nice fact is, Go also help you create benchmark easy.
Still in the test file, but use Benchmark
as a prefix of a test.
package add
func BenchmarkAdd(b *testing.B) {
for i := 0; i < b.N; i++ {
Add(1, 2)
}
}
To run the benchmark needs argument -bench
, it would like go test -bench .
Output:
goos: darwin
goarch: amd64
pkg: test
BenchmarkAdd-4 2000000000 0.61 ns/op
PASS
ok test 1.285s
As t.Run
, you can have b.Run
in the benchmark.
To get a nice analysis of the program, you can use go test -bench . -cpuprofile cpu.out -memprofile mem.out
to generate some profiles
Then use go tool pprof -http=127.0.0.1:5000 cpu.out
to see the result on the browser(if you are familiar with CLI mode, you can remove -http
flag)
You can see something like:
----------------------------------------------------------+-------------
1130ms 100% | testing.(*B).launch /usr/local/Cellar/go/1.11.2/libexec/src/testing/benchmark.go:290
0 0% 100% 1130ms 98.26% | testing.(*B).runN /usr/local/Cellar/go/1.11.2/libexec/src/testing/benchmark.go:141
1130ms 100% | test.BenchmarkAdd /Users/dannypsnl/code/go/src/test/add_test.go:8
----------------------------------------------------------+-------------
At here example is too easy so nothing to show, in a real-world code it would be pretty useful to know the hot point of the program.
p.s. At profile example,
-bench
can’t be omitted, because we want something to run lots of time to detect it’s real performance.
If you want to get the performance under real usage, you can import pprof into the program:
import (
_ "net/http/pprof"
)
If your program is not an HTTP server, then you have to start one like:
go func() {
log.Println(http.ListenAndServe("0.0.0.0:6060", nil))
}()
The reason of 0.0.0.0
can reference to https://stackoverflow.com/questions/20778771/what-is-the-difference-between-0-0-0-0-127-0-0-1-and-localhost
After these, you can run your program up then see your profile like go tool pprof http://127.0.0.1:6060/debug/pprof/profile
To get more info, you can reference:
Thanks for reading
Top comments (4)
Seems need to write package name and put under src dir.
My fault, should write more complete info XD
Thanks for share, hope to see more awesome posts in Go from you.
Thank you for this. I love testing and Golang; your examples are nice and simple to get started with.