Add test coverage for vhd; make commands and filesystem abstractable

internal/vhd/vhd.go

@@ -8,45 +8,108 @@ import (
 	"strings"
 
 	"emperror.dev/errors"
+	"github.com/spf13/afero"
 )
 
 var (
+	ErrPathNotDirectory  = errors.Sentinel("vhd: filesystem path is not a directory")
 	ErrFilesystemMounted = errors.Sentinel("vhd: filesystem is already mounted")
 	ErrFilesystemExists  = errors.Sentinel("vhd: filesystem already exists on disk")
 )
 
+// hasExitCode allows this code to test the response error to see if there is
+// an exit code available from the command call that can be used to determine if
+// something went wrong.
+type hasExitCode interface {
+	ExitCode() int
+}
+
+// Commander defines an interface that must be met for executing commands on the
+// underlying OS. By default the vhd package will use Go's exec.Cmd type for
+// execution. This interface allows stubbing out on tests, or potentially custom
+// setups down the line.
+type Commander interface {
+	Run() error
+	Output() ([]byte, error)
+	String() string
+}
+
+// CommanderProvider is a function that provides a struct meeting the Commander
+// interface requirements.
+type CommanderProvider func(ctx context.Context, name string, args ...string) Commander
+
+// CfgOption is a configuration option callback for the Disk.
+type CfgOption func(d *Disk) *Disk
+
+// Disk represents the underlying virtual disk for the instance.
 type Disk struct {
 	size      int64
-
 	diskPath  string
 	mountAt   string
+	fs        afero.Fs
+	commander CommanderProvider
 }
 
 // New returns a new Disk instance. The "size" parameter should be provided in
-// megabytes of space allowed for the disk.
-func New(size int64, diskPath string, mountAt string) *Disk {
+// megabytes of space allowed for the disk. An additional slice of option
+// callbacks can be provided to programatically swap out the underlying filesystem
+// implementation or the underlying command exection engine.
+func New(size int64, diskPath string, mountAt string, opts ...func(*Disk)) *Disk {
 	if diskPath == "" || mountAt == "" {
 		panic("vhd: cannot specify an empty disk or mount path")
 	}
-	return &Disk{size, diskPath, mountAt}
+	d := Disk{
+		size:     size,
+		diskPath: diskPath,
+		mountAt:  mountAt,
+		fs:       afero.NewOsFs(),
+		commander: func(ctx context.Context, name string, args ...string) Commander {
+			return exec.CommandContext(ctx, name, args...)
+		},
+	}
+	for _, opt := range opts {
+		opt(&d)
+	}
+	return &d
+}
+
+// WithFs allows for a different underlying filesystem to be provided to the
+// virtual disk manager.
+func WithFs(fs afero.Fs) func(*Disk) {
+	return func(d *Disk) {
+		d.fs = fs
+	}
+}
+
+// WithCommander allows a different Commander provider to be provided.
+func WithCommander(c CommanderProvider) func(*Disk) {
+	return func(d *Disk) {
+		d.commander = c
+	}
 }
 
 // Exists reports if the disk exists on the system yet or not. This only verifies
-// the presence of the disk image, not the validity of it.
+// the presence of the disk image, not the validity of it. An error is returned
+// if the provided disk path exists but is not a directory.
 func (d *Disk) Exists() (bool, error) {
-	_, err := os.Lstat(d.diskPath)
-	if err == nil || os.IsNotExist(err) {
-		return err == nil, nil
-	}
+	st, err := d.fs.Stat(d.diskPath)
+	if err != nil && os.IsNotExist(err) {
+		return false, nil
+	} else if err != nil {
 		return false, errors.WithStack(err)
+	}
+	if st.IsDir() {
+		return true, nil
+	}
+	return false, errors.WithStack(ErrPathNotDirectory)
 }
 
 // IsMounted checks to see if the given disk is currently mounted.
 func (d *Disk) IsMounted(ctx context.Context) (bool, error) {
 	find := d.mountAt + " ext4"
-	cmd := exec.CommandContext(ctx, "grep", "-qs", find, "/proc/mounts")
+	cmd := d.commander(ctx, "grep", "-qs", find, "/proc/mounts")
 	if err := cmd.Run(); err != nil {
-		if v, ok := err.(*exec.ExitError); ok {
+		if v, ok := err.(hasExitCode); ok {
 			if v.ExitCode() == 1 {
 				return false, nil
 			}
@@ -64,19 +127,21 @@ func (d *Disk) IsMounted(ctx context.Context) (bool, error) {
 // returned to the caller. If the disk is already mounted an ErrFilesystemMounted
 // error is returned to the caller.
 func (d *Disk) Mount(ctx context.Context) error {
-	if _, err := os.Lstat(d.mountAt); err != nil && !os.IsNotExist(err) {
+	if st, err := d.fs.Stat(d.mountAt); err != nil && !os.IsNotExist(err) {
 		return errors.Wrap(err, "vhd: failed to stat mount path")
 	} else if os.IsNotExist(err) {
-		if err := os.MkdirAll(d.mountAt, 0600); err != nil {
+		if err := d.fs.MkdirAll(d.mountAt, 0600); err != nil {
 			return errors.Wrap(err, "vhd: failed to create mount path")
 		}
+	} else if !st.IsDir() {
+		return errors.WithStack(ErrPathNotDirectory)
 	}
 	if isMounted, err := d.IsMounted(ctx); err != nil {
 		return errors.WithStackIf(err)
 	} else if isMounted {
 		return ErrFilesystemMounted
 	}
-	cmd := exec.CommandContext(ctx, "mount", "-t", "auto", "-o", "loop", d.diskPath, d.mountAt)
+	cmd := d.commander(ctx, "mount", "-t", "auto", "-o", "loop", d.diskPath, d.mountAt)
 	if _, err := cmd.Output(); err != nil {
 		msg := "vhd: failed to mount disk"
 		if v, ok := err.(*exec.ExitError); ok {
@@ -91,9 +156,9 @@ func (d *Disk) Mount(ctx context.Context) error {
 // currently mounted this function is a no-op and no error is returned. Any
 // other error encountered while unmounting will return an error to the caller.
 func (d *Disk) Unmount(ctx context.Context) error {
-	cmd := exec.CommandContext(ctx, "umount", d.mountAt)
+	cmd := d.commander(ctx, "umount", d.mountAt)
 	if err := cmd.Run(); err != nil {
-		if v, ok := err.(*exec.ExitError); !ok || v.ExitCode() != 32 {
+		if v, ok := err.(hasExitCode); !ok || v.ExitCode() != 32 {
 			return errors.Wrap(err, "vhd: failed to execute unmount command for disk")
 		}
 	}
@@ -116,8 +181,7 @@ func (d *Disk) Allocate(ctx context.Context) error {
 	} else if err != nil {
 		return errors.Wrap(err, "vhd: failed to check for existence of root disk")
 	}
-	cmd := exec.CommandContext(ctx, "fallocate", "-l", fmt.Sprintf("%dM", d.size), d.diskPath)
-	fmt.Println(cmd.String())
+	cmd := d.commander(ctx, "fallocate", "-l", fmt.Sprintf("%dM", d.size), d.diskPath)
 	if _, err := cmd.Output(); err != nil {
 		msg := "vhd: failed to execute fallocate command"
 		if v, ok := err.(*exec.ExitError); ok {
@@ -154,7 +218,7 @@ func (d *Disk) MakeFilesystem(ctx context.Context) error {
 	// Because this is a destructive command and non-tty based exection of it implies
 	// "-F" (force), we need to only run it when we can guarantee it doesn't already
 	// exist. No vague "maybe that error is expected" allowed here.
-	cmd := exec.CommandContext(ctx, "mkfs", "-t", "ext4", d.diskPath)
+	cmd := d.commander(ctx, "mkfs", "-t", "ext4", d.diskPath)
 	if err := cmd.Run(); err != nil {
 		return errors.Wrap(err, "vhd: failed to make filesystem for disk")
 	}

internal/vhd/vhd_test.go

@@ -0,0 +1,472 @@
+package vhd
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type mockCmd struct {
+	run    func() error
+	output func() ([]byte, error)
+	string func() string
+}
+
+func (m *mockCmd) Run() error {
+	if m.run != nil {
+		return m.run()
+	}
+	return nil
+}
+
+func (m *mockCmd) Output() ([]byte, error) {
+	if m.output != nil {
+		return m.output()
+	}
+	return nil, nil
+}
+
+func (m *mockCmd) String() string {
+	if m.string != nil {
+		return m.string()
+	}
+	return ""
+}
+
+var _ Commander = (*mockCmd)(nil)
+
+type mockedExitCode struct {
+	code int
+}
+
+func (m *mockedExitCode) ExitCode() int {
+	return m.code
+}
+
+func (m *mockedExitCode) Error() string {
+	return fmt.Sprintf("mocked exit code: code %d", m.code)
+}
+
+func newMockDisk(c CommanderProvider) *Disk {
+	commander := func(ctx context.Context, name string, args ...string) Commander {
+		return &mockCmd{}
+	}
+	w := commander
+	if c != nil {
+		w = c
+	}
+	return New(100, "/foo", "/bar", WithFs(afero.NewMemMapFs()), WithCommander(w))
+}
+
+func Test_New(t *testing.T) {
+	t.Run("creates expected struct", func(t *testing.T) {
+		d := New(100, "/foo", "/bar")
+		assert.NotNil(t, d)
+		assert.Equal(t, int64(100), d.size)
+		assert.Equal(t, "/foo", d.diskPath)
+		assert.Equal(t, "/bar", d.mountAt)
+
+		// Ensure by default we get a commander interface returned and that it
+		// returns an *exec.Cmd.
+		o := d.commander(context.TODO(), "foo", "-bar")
+		assert.NotNil(t, o)
+		_, ok := o.(Commander)
+		assert.True(t, ok)
+		_, ok = o.(*exec.Cmd)
+		assert.True(t, ok)
+	})
+
+	t.Run("creates an instance with custom options", func(t *testing.T) {
+		fs := afero.NewMemMapFs()
+
+		cprov := struct {
+			Commander
+		}{}
+		c := func(ctx context.Context, name string, args ...string) Commander {
+			return &cprov
+		}
+
+		d := New(100, "/foo", "/bar", WithFs(fs), WithCommander(c))
+		assert.NotNil(t, d)
+		assert.Same(t, fs, d.fs)
+		assert.Same(t, &cprov, d.commander(context.TODO(), ""))
+	})
+
+	t.Run("panics if either path is empty", func(t *testing.T) {
+		assert.Panics(t, func() {
+			_ = New(100, "", "/bar")
+		})
+
+		assert.Panics(t, func() {
+			_ = New(100, "/foo", "")
+		})
+	})
+}
+
+func TestDisk_Exists(t *testing.T) {
+	t.Run("it exists", func(t *testing.T) {
+		d := newMockDisk(nil)
+		err := d.fs.Mkdir("/foo", 0600)
+		require.NoError(t, err)
+
+		exists, err := d.Exists()
+		assert.NoError(t, err)
+		assert.True(t, exists)
+	})
+
+	t.Run("it does not exist", func(t *testing.T) {
+		d := newMockDisk(nil)
+		exists, err := d.Exists()
+		assert.NoError(t, err)
+		assert.False(t, exists)
+	})
+
+	t.Run("it reports errors", func(t *testing.T) {
+		d := newMockDisk(nil)
+		_, err := d.fs.Create("/foo")
+		require.NoError(t, err)
+
+		exists, err := d.Exists()
+		assert.Error(t, err)
+		assert.False(t, exists)
+		assert.EqualError(t, err, ErrPathNotDirectory.Error())
+	})
+}
+
+func TestDisk_IsMounted(t *testing.T) {
+	t.Run("executes command and finds mounted disk", func(t *testing.T) {
+		is := assert.New(t)
+		var called bool
+
+		pctx := context.TODO()
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			called = true
+			is.Same(pctx, ctx)
+			is.Equal("grep", name)
+			is.Len(args, 3)
+			is.Equal([]string{"-qs", "/bar ext4", "/proc/mounts"}, args)
+
+			return &mockCmd{}
+		}
+
+		disk := newMockDisk(cmd)
+		mnt, err := disk.IsMounted(pctx)
+		is.NoError(err)
+		is.True(mnt)
+		is.True(called)
+	})
+
+	t.Run("handles exit code 1 gracefully", func(t *testing.T) {
+		var called bool
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			called = true
+			return &mockCmd{
+				run: func() error {
+					return &mockedExitCode{code: 1}
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		mnt, err := disk.IsMounted(context.TODO())
+		assert.NoError(t, err)
+		assert.False(t, mnt)
+		assert.True(t, called)
+	})
+
+	t.Run("handles unexpected errors successfully", func(t *testing.T) {
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					return &mockedExitCode{code: 3}
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		mnt, err := disk.IsMounted(context.TODO())
+		assert.Error(t, err)
+		assert.False(t, mnt)
+	})
+}
+
+func TestDisk_Mount(t *testing.T) {
+	t.Run("error is returned if mount point is not a directory", func(t *testing.T) {
+		disk := newMockDisk(nil)
+		_, err := disk.fs.Create("/bar")
+		require.NoError(t, err)
+
+		err = disk.Mount(context.TODO())
+		assert.Error(t, err)
+		assert.EqualError(t, err, ErrPathNotDirectory.Error())
+	})
+
+	t.Run("error is returned if mount point cannot be created", func(t *testing.T) {
+		disk := newMockDisk(nil)
+		disk.fs = afero.NewReadOnlyFs(disk.fs)
+
+		err := disk.Mount(context.TODO())
+		assert.Error(t, err)
+		assert.EqualError(t, err, "vhd: failed to create mount path: operation not permitted")
+	})
+
+	t.Run("error is returned if already mounted", func(t *testing.T) {
+		disk := newMockDisk(nil)
+		err := disk.Mount(context.TODO())
+		assert.Error(t, err)
+		assert.EqualError(t, err, ErrFilesystemMounted.Error())
+	})
+
+	t.Run("error is returned if mount command fails", func(t *testing.T) {
+		var called bool
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					return &mockedExitCode{code: 1}
+				},
+				output: func() ([]byte, error) {
+					called = true
+
+					assert.Equal(t, "mount", name)
+					assert.Equal(t, []string{"-t", "auto", "-o", "loop", "/foo", "/bar"}, args)
+
+					return nil, &exec.ExitError{
+						ProcessState: &os.ProcessState{},
+						Stderr: []byte("foo bar.\n"),
+					}
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.Mount(context.TODO())
+		assert.Error(t, err)
+		assert.EqualError(t, err, "vhd: failed to mount disk: foo bar: exit status 0")
+		assert.True(t, called)
+	})
+
+	t.Run("disk can be mounted at existing path", func(t *testing.T) {
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					return &mockedExitCode{code: 1}
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		require.NoError(t, disk.fs.Mkdir("/bar", 0600))
+
+		err := disk.Mount(context.TODO())
+		assert.NoError(t, err)
+	})
+
+	t.Run("disk can be mounted at non-existing path", func(t *testing.T) {
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					return &mockedExitCode{code: 1}
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.Mount(context.TODO())
+		assert.NoError(t, err)
+
+		st, err := disk.fs.Stat("/bar")
+		assert.NoError(t, err)
+		assert.True(t, st.IsDir())
+	})
+}
+
+func TestDisk_Unmount(t *testing.T) {
+	t.Run("can unmount a disk", func(t *testing.T) {
+		is := assert.New(t)
+		pctx := context.TODO()
+
+		var called bool
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			called = true
+
+			is.Same(pctx, ctx)
+			is.Equal("umount", name)
+			is.Equal([]string{"/bar"}, args)
+
+			return &mockCmd{}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.Unmount(pctx)
+		is.NoError(err)
+		is.True(called)
+	})
+
+	t.Run("handles exit code 32 correctly", func(t *testing.T) {
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					return &mockedExitCode{code: 32}
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.Unmount(context.TODO())
+		assert.NoError(t, err)
+	})
+
+	t.Run("non code 32 errors are returned as error", func(t *testing.T) {
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					return &mockedExitCode{code: 1}
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.Unmount(context.TODO())
+		assert.Error(t, err)
+	})
+
+	t.Run("errors without ExitCode function are returned", func(t *testing.T) {
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					return errors.New("foo bar")
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.Unmount(context.TODO())
+		assert.Error(t, err)
+	})
+}
+
+func TestDisk_Allocate(t *testing.T) {
+	t.Run("disk is unmounted before allocating space", func(t *testing.T) {
+		var called bool
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				output: func() ([]byte, error) {
+					called = true
+					assert.Equal(t, "fallocate", name)
+					assert.Equal(t, []string{"-l", "100M", "/foo"}, args)
+					return nil, nil
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.fs.Mkdir("/foo", 0600)
+		require.NoError(t, err)
+
+		err = disk.Allocate(context.TODO())
+		assert.NoError(t, err)
+		assert.True(t, called)
+	})
+
+	t.Run("disk space is allocated even when not exists", func(t *testing.T) {
+		disk := newMockDisk(nil)
+		err := disk.Allocate(context.TODO())
+		assert.NoError(t, err)
+	})
+
+	t.Run("error is returned if command fails", func(t *testing.T) {
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				output: func() ([]byte, error) {
+					return nil, &exec.ExitError{
+						ProcessState: &os.ProcessState{},
+						Stderr: []byte("foo bar.\n"),
+					}
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.fs.Mkdir("/foo", 0600)
+		require.NoError(t, err)
+
+		err = disk.Allocate(context.TODO())
+		assert.Error(t, err)
+		assert.EqualError(t, err, "vhd: failed to execute fallocate command: foo bar: exit status 0")
+	})
+}
+
+func TestDisk_MakeFilesystem(t *testing.T) {
+	t.Run("filesystem is created if not found in /etc/fstab", func(t *testing.T) {
+		var called bool
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					// Expect the call from IsMounted here and just return what we need
+					// to indicate that nothing is currently mounted.
+					if name == "grep" {
+						return &mockedExitCode{code: 1}
+					}
+					called = true
+					assert.Equal(t, "mkfs", name)
+					assert.Equal(t, []string{"-t", "ext4", "/foo"}, args)
+					return nil
+				},
+				output: func() ([]byte, error) {
+					return nil, errors.New("error: can't find in /etc/fstab foo bar testing")
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.MakeFilesystem(context.TODO())
+		assert.NoError(t, err)
+		assert.True(t, called)
+	})
+
+	t.Run("filesystem is created if error is returned from mount command", func(t *testing.T) {
+		var called bool
+		var cmd CommanderProvider = func(ctx context.Context, name string, args ...string) Commander {
+			return &mockCmd{
+				run: func() error {
+					// Expect the call from IsMounted here and just return what we need
+					// to indicate that nothing is currently mounted.
+					if name == "grep" {
+						return &mockedExitCode{code: 1}
+					}
+					called = true
+					assert.Equal(t, "mkfs", name)
+					assert.Equal(t, []string{"-t", "ext4", "/foo"}, args)
+					return nil
+				},
+				output: func() ([]byte, error) {
+					if name == "mount" {
+						return nil, &exec.ExitError{
+							Stderr: []byte("foo bar: exit status 32\n"),
+						}
+					}
+					return nil, nil
+				},
+			}
+		}
+
+		disk := newMockDisk(cmd)
+		err := disk.MakeFilesystem(context.TODO())
+		assert.NoError(t, err)
+		assert.True(t, called)
+	})
+
+	t.Run("error is returned if currently mounted", func(t *testing.T) {
+		disk := newMockDisk(nil)
+		err := disk.MakeFilesystem(context.TODO())
+		assert.Error(t, err)
+		assert.EqualError(t, err, ErrFilesystemExists.Error())
+	})
+}