How to use go's TestMain with terratest?

[michalschott]

I have very similar problem described here.

My use case is I'd like to pre-create few resources (VPC, Route53 zone) so other tests can use these.

So far I have managed to do this:

func TestMain(m *testing.M) {
	t := &testing.T{}

	// create vpc
	vpcTestSource := test_structure.CopyTerraformFolderToTemp(t, "../../", "modules/aws/vpc")
	vpcTerraformOptions := terraform.WithDefaultRetryableErrors(t, &terraform.Options{
		TerraformDir: vpcTestSource,
		Vars: map[string]interface{}{
                  ...
		},
		EnvVars: map[string]string{
			"AWS_DEFAULT_REGION": awsRegion,
		},
	})
	defer terraform.Destroy(t, vpcTerraformOptions)
	terraform.InitAndApplyAndIdempotent(t, vpcTerraformOptions)
}

Altho if terraform apply in above snippet fails, looks like test is waiting for timeout actually to happen. Suspect it happens due to "custom" testing.T object.

[yorinasub17]

Unfortunately this is currently not a supported mode of operation in terratest, primarily because we rely on the t struct to do various things like logging and test failing on errors. We will need a version of each function that is optimized for testing.M instead of testing.T to make this work.

We are a bit buried to take this on, so I suspect this won't get implemented in the short term, unless someone from the community is willing to take it.

[michalschott]

@yorinasub17 I have been using below snippet (slightly modified from what I have originally pasted above) and it runs flawlessly so far:

func TestMain(m *testing.M) {
	t := &testing.T{}

	// create vpc
	fmt.Printf("Preparing VPC %s\n", testSuite.stage)
	vpcTestSource := test_structure.CopyTerraformFolderToTemp(t, "../../", "modules/aws/networking")
	vpcTerraformOptions := terraform.WithDefaultRetryableErrors(t, &terraform.Options{
		TerraformDir: vpcTestSource,
		Vars: map[string]interface{}{
			...
		},
		EnvVars: map[string]string{
			...
		},
	})
	defer terraform.Destroy(t, vpcTerraformOptions)
	if _, err := terraform.InitAndApplyAndIdempotentE(t, vpcTerraformOptions); err != nil {
		terraform.Destroy(t, vpcTerraformOptions)
		os.Exit(1)
	}

	// assertions for VPC module
      
	// run all the tests
	m.Run()
}

I was also looking at beforeEach approach to create VPCs, but this does not scale well in my use case since VPC creation with all dependencies takes approx 5-8 minutes.

[yorinasub17]

I have been using below snippet (slightly modified from what I have originally pasted above) and it runs flawlessly so far:

If you have a working solution, then that's great! Does that solve your original problem of apply hanging when there is an error?

I was also looking at beforeEach approach to create VPCs, but this does not scale well in my use case since VPC creation with all dependencies takes approx 5-8 minutes.

Ah, FWIW, the main way the Gruntwork team addresses this is by using subtests. It's not ideal due to the various gotchas around t.Parallel, but it works for the most part:

func TestAllThatNeedVPC(t *testing.T) {
    t.Parallel()

    vpcOpts := createVPCTerraforOptions(t)
    defer terraform.Destroy(t, vpcOpts)
    terraform.InitAndApply(t, vpcOpts)

    // We wrap all the subtests in a synchronous grouped test (not calling t.Parallel)
    // so that all the subtests in the group finish before returning control to the main thread.
    t.Run("group", func(t *testing.T) {
        t.Run("TestOneThatNeedsVPC", func(t *testing.T) {
            t.Parallel()
            testOneThatNeedsVPC(t, vpcOpts)
        })
        t.Run("TestTwoThatNeedsVPC", func(t *testing.T) {
            t.Parallel()
            testTwoThatNeedsVPC(t, vpcOpts)
        })
        // ... and so on ...
    })
}