golang testing method after each test: undefined: testing.M

Question

I am trying to repeat example from golang testing

package main

import (
    "testing"
)

func TestSomeTest(t *testing.T) {}

func TestMain(m *testing.M) { // cleaning after each test}

I want TestMain function to run after every test.

Running command go test

And the compiler says

./testingM_test.go:9: undefined: testing.M

So how to clean after executing every test?

Answer 1

Check you go version output: this is for go 1.4+ only.

The testing package has a new facility to provide more control over running a set of tests. If the test code contains a function

func TestMain(m *testing.M) 

that function will be called instead of running the tests directly.
The M struct contains methods to access and run the tests.

---

You can see that feature used here:

The introduction of TestMain() made it possible to run these migrations only once. The code now looks like this:

func TestSomeFeature(t *testing.T) {
    defer models.TestDBManager.Reset()

    // Do the tests
}

func TestMain(m *testing.M) {
    models.TestDBManager.Enter()
    // os.Exit() does not respect defer statements
    ret := m.Run()
    models.TestDBManager.Exit()
    os.Exit(ret)
}

While each test must still clean up after itself, that only involves restoring the initial data, which is way faster than doing the schema migrations.