I’m writing unit tests in go. In a function I’m using an ApplyString to extract the string out of the StringOutput, When testing I’m seeing and I’m not sure what it means, or how to fix it

panic: applier must have 1 input parameter assignable from interface {} [recovered]
	panic: applier must have 1 input parameter assignable from interface {}

Can you share the code/repro?

yup. i think this should capture the intent:

// create a new network
func (resource *Network) create(ctx *pulumi.Context, name string, args *NetworkArgs) error {

	var err error

	resource.Vpc, err = args.VpcCreator(ctx, name+"-vpc", &ec2.VpcArgs{
		CidrBlock:                   pulumi.String("10.99.0.0/16"),
		EnableDnsHostnames:          pulumi.Bool(true),
		EnableClassiclinkDnsSupport: pulumi.Bool(true),
	}, pulumi.Parent(resource))
	if err != nil {
		return errors.Wrap(err, "Cannot create VPC")
	}

	_ = resource.Vpc.DefaultSecurityGroupId.ApplyString(func(s string) string {
		resource.SecurityGroupIds = append(resource.SecurityGroupIds, s)
		return s
	})

  // ...
}

// test code

t.Run("create adds default security group to network", func(t *testing.T) {

  mock := mock{}

  n := Network{}
  fakeVpc := &ec2.Vpc{}

  expects := []string{fakeVpc.DefaultSecurityGroupId}

  args := &NetworkArgs{
    NumAvailabilityZones:   2,
    VpcCreator:             mock.FakeVpcCreator(fakeVpc, nil),
  }

  err := n.create(ctx, name, args)
  assert.Equal(t, expects, n.SecurityGroupIds)

  ...
})

Have you taken a look at the example? You'll need to implement

NewResource

and other mocks https://github.com/pulumi/examples/blob/master/testing-unit-go/main_test.go#L16-L22

Yup. I have mocks in place already. The

t.Run

’s live inside a

err := pulumi.RunErr

that’s passing in mocks