add UT for createDisk func about azurefile-csi-driver

[andyzhangx]

/assign @ZeroMagic

[ZeroMagic]

Need to add a mock file Client in the fake cloud firstly.
https://github.com/kubernetes/kubernetes/blob/b461633ff0534089f6bd98aea1cd4df596091b75/staging/src/k8s.io/legacy-cloud-providers/azure/azure_fakes.go#L47

[kushthedude]

Hi @andyzhangx, I would like to solve this issue. Can you provide additional details on Unit Tests that need to be added for the following functions?

[andyzhangx]

@animeshk08 could you also take a look at this? thanks.

[animeshk08]

The unit tests already exist here:

azurefile-csi-driver/pkg/azurefile/azurefile_test.go

Line 605 in f0a7d58

func TestCreateDisk(t *testing.T) {

Line coverage can be found here: https://coveralls.io/builds/32107068/source?filename=pkg/azurefile/azurefile.go#L364

Only lines 384-387 are prominently remaining, which cannot yet be covered due to the absence of the mock interface(see here).

[andyzhangx]

thanks