controller/vm: add unit tests for VM Controller state machine

[shreyanshjain7174]

Depends on #2627 — must merge first.

Adds unit tests for the VM Controller state machine (internal/controller/vm/). To make the Manager testable, two field types are changed to their existing interfaces (vmmanager.LifetimeManager, combined GuestManager). Mocks are generated with mockgen following the internal/windows/mock/ pattern.

Tests are biased toward production failure paths — resource cleanup, state corruption, and half-started scenarios — rather than guard-check permutations.

30 test cases covering: TerminateVM transitions (idempotency, Created/Running→Terminated, Close fail→Invalid, Invalid recovery, Terminate() error swallowed with Close still called, CloseConnection() error swallowed with Close still called), CreateVM duplicate-call rejection, StartVM failure paths (uvm.Start fails→Invalid, listener/connection failure→Invalid, idempotency when already Running, wrong-state rejection), ExecIntoHost (terminal+stderr precondition, success, exec error), DumpStacks (supported, not supported, dump error), StartTime/ExitStatus for relevant states, representative guard checks (one per method for realistic wrong-state calls), and State.String() for all values. All tests run without admin or HCS.

[rawahars]

Please remove this comment. The idea identified here is implicit for V2 shims and therefore, this just adds noise.

[rawahars]

rename this to utilityVM

[rawahars]

You do not need to declare the interface for each variant.
You can use approach similar to how it's done here-

hcsshim/internal/controller/vm/vm.go

Line 69 in fa5c029

platformControllers //nolint:unused,nolintlint // embedded for cross-platform compatibility; empty on WCOW

Idea is keep the common APIs in types.go and then platform specific ones in vm_lcow and vm_wcow.
types.go

type utilityVM interface {
	ID() string
	RuntimeID() guid.GUID
	Start(ctx context.Context) error
	Wait(ctx context.Context) error
	Terminate(ctx context.Context) error
	Close(ctx context.Context) error
	SetCPUGroup(ctx context.Context, settings *hcsschema.CpuGroup) error
	UpdateCPULimits(ctx context.Context, settings *hcsschema.ProcessorLimits) error
	UpdateMemory(ctx context.Context, memory uint64) error
	PropertiesV2(ctx context.Context, types ...hcsschema.PropertyType) (*hcsschema.Properties, error)
	StartedTime() time.Time
	StoppedTime() time.Time
	ExitError() error

	AddDevice(ctx context.Context, vmbusGUID guid.GUID, settings hcsschema.VirtualPciDevice) error
	RemoveDevice(ctx context.Context, vmbusGUID guid.GUID) error
	AddNIC(ctx context.Context, nicID string, settings *hcsschema.NetworkAdapter) error
	RemoveNIC(ctx context.Context, nicID string, settings *hcsschema.NetworkAdapter) error
	AddSCSIDisk(ctx context.Context, disk hcsschema.Attachment, controller uint, lun uint) error
	RemoveSCSIDisk(ctx context.Context, controller uint, lun uint) error

    // Platform specific APIs
    platformUVM
}

type guestManager interface {
	CreateConnection(ctx context.Context, gcsServiceID guid.GUID, opts ...guestmanager.ConfigOption) error
	CloseConnection() error
	AddSecurityPolicy(ctx context.Context, opts guestresource.ConfidentialOptions) error
	InjectPolicyFragment(ctx context.Context, fragment guestresource.SecurityPolicyFragment) error
	Capabilities() gcs.GuestDefinedCapabilities
	DumpStacks(ctx context.Context) (string, error)
	ExecIntoUVM(ctx context.Context, request *cmd.CmdProcessRequest) (int, error)

    // Platform specific APIs
    platformGuestManager 
}

vm_lcow.go

type platformUVM interface {
    // LCOW-specific methods
	AddPlan9(ctx context.Context, settings hcsschema.Plan9Share) error
	RemovePlan9(ctx context.Context, settings hcsschema.Plan9Share) error
}

type platformGuestManager interface {
    // LCOW-specific methods
	AddVPCIDevice(ctx context.Context, settings guestresource.LCOWMappedVPCIDevice) error
	AddNetworkInterface(ctx context.Context, settings *guestresource.LCOWNetworkAdapter) error
	RemoveNetworkInterface(ctx context.Context, settings *guestresource.LCOWNetworkAdapter) error
	AddMappedDirectory(ctx context.Context, settings guestresource.LCOWMappedDirectory) error
	RemoveMappedDirectory(ctx context.Context, settings guestresource.LCOWMappedDirectory) error
	AddMappedVirtualDisk(ctx context.Context, settings guestresource.LCOWMappedVirtualDisk) error
	RemoveMappedVirtualDisk(ctx context.Context, settings guestresource.LCOWMappedVirtualDisk) error
	RemoveSCSIDevice(ctx context.Context, settings guestresource.SCSIDevice) error
}

vm_wcow.go

type platformUVM interface {
}

type platformGuestManager interface {
	// WCOW-specific methods
	UpdateHvSocketAddress(ctx context.Context, address *hcsschema.HvSocketAddress) error
	AddNetworkInterface(ctx context.Context, adapterID string, requestType guestrequest.RequestType, settings *hcn.HostComputeEndpoint) error
	RemoveNetworkInterface(ctx context.Context, adapterID string, requestType guestrequest.RequestType, settings *hcn.HostComputeEndpoint) error
	AddNetworkNamespace(ctx context.Context, settings *hcn.HostComputeNamespace) error
	RemoveNetworkNamespace(ctx context.Context, settings *hcn.HostComputeNamespace) error
	AddMappedVirtualDisk(ctx context.Context, settings guestresource.WCOWMappedVirtualDisk) error
	AddMappedVirtualDiskForContainerScratch(ctx context.Context, settings guestresource.WCOWMappedVirtualDisk) error
	RemoveMappedVirtualDisk(ctx context.Context, settings guestresource.WCOWMappedVirtualDisk) error
}

[rawahars]

Second thoughts- Please see the uber review comment.

[rawahars]

Please rebase on current main. There is one more Guest API- PrepareConnection.

[rawahars]

The interface segregation can be simplified. You can possibly cherry-pick rawahars@1ca1a08

This refactors the VM controller to use interfaces.