test: Refactor mock CSI manager (#18554)

and MockCSIManager to support the call counting
that csi_hook_test expects

instead of implementing csimanager
interfaces in two separate places:
* client/allocrunner/csi_hook_test
* client/csi_endpoint_test

they can both use the same mocks defined in
client/pluginmanager/csimanager/
alongside the actual implementations of them.

also refactor TestCSINode_DetachVolume
to use use it like Node_ExpandVolume
so we can also test the happy path there

client/pluginmanager/csimanager/testing.go

@@ -5,10 +5,12 @@ package csimanager
 
 import (
 	"context"
+	"path/filepath"
 
 	"github.com/hashicorp/nomad/client/pluginmanager"
 	nstructs "github.com/hashicorp/nomad/nomad/structs"
 	"github.com/hashicorp/nomad/plugins/csi"
+	"github.com/hashicorp/nomad/testutil"
 )
 
 var _ Manager = &MockCSIManager{}
@@ -29,6 +31,9 @@ func (m *MockCSIManager) WaitForPlugin(_ context.Context, pluginType, pluginID s
 }
 
 func (m *MockCSIManager) ManagerForPlugin(_ context.Context, pluginID string) (VolumeManager, error) {
+	if m.VM == nil {
+		m.VM = &MockVolumeManager{}
+	}
 	return m.VM, m.NextManagerForPluginErr
 }
 
@@ -39,20 +44,68 @@ func (m *MockCSIManager) Shutdown() {
 var _ VolumeManager = &MockVolumeManager{}
 
 type MockVolumeManager struct {
+	CallCounter *testutil.CallCounter
+
+	Mounts map[string]bool // lazy set
+
+	NextMountVolumeErr   error
+	NextUnmountVolumeErr error
+
 	NextExpandVolumeErr  error
 	LastExpandVolumeCall *MockExpandVolumeCall
 }
 
+func (m *MockVolumeManager) mountName(volID, allocID string, usageOpts *UsageOptions) string {
+	return filepath.Join("test-alloc-dir", allocID, volID, usageOpts.ToFS())
+}
+
 func (m *MockVolumeManager) MountVolume(_ context.Context, vol *nstructs.CSIVolume, alloc *nstructs.Allocation, usageOpts *UsageOptions, publishContext map[string]string) (*MountInfo, error) {
-	panic("implement me")
+	if m.CallCounter != nil {
+		m.CallCounter.Inc("MountVolume")
+	}
+
+	if m.NextMountVolumeErr != nil {
+		err := m.NextMountVolumeErr
+		m.NextMountVolumeErr = nil // reset it
+		return nil, err
+	}
+
+	// "mount" it
+	if m.Mounts == nil {
+		m.Mounts = make(map[string]bool)
+	}
+	source := m.mountName(vol.ID, alloc.ID, usageOpts)
+	m.Mounts[source] = true
+
+	return &MountInfo{
+		Source: source,
+	}, nil
 }
 
 func (m *MockVolumeManager) UnmountVolume(_ context.Context, volID, remoteID, allocID string, usageOpts *UsageOptions) error {
-	panic("implement me")
+	if m.CallCounter != nil {
+		m.CallCounter.Inc("UnmountVolume")
+	}
+
+	if m.NextUnmountVolumeErr != nil {
+		err := m.NextUnmountVolumeErr
+		m.NextUnmountVolumeErr = nil // reset it
+		return err
+	}
+
+	// "unmount" it
+	delete(m.Mounts, m.mountName(volID, allocID, usageOpts))
+	return nil
 }
 
 func (m *MockVolumeManager) HasMount(_ context.Context, mountInfo *MountInfo) (bool, error) {
-	panic("implement me")
+	if m.CallCounter != nil {
+		m.CallCounter.Inc("HasMount")
+	}
+	if m.Mounts == nil {
+		return false, nil
+	}
+	return m.Mounts[mountInfo.Source], nil
 }
 
 func (m *MockVolumeManager) ExpandVolume(_ context.Context, volID, remoteID, allocID string, usageOpts *UsageOptions, capacity *csi.CapacityRange) (int64, error) {