command: add tests for container diff and rename

This commit adds tests for the commands
docker diff and docker rename. Also,
it creates the mock methods of the
docker client ContainerDiff and
ContainerRename so they can
be used in the tests.

For docker diff, it covers the
cases that:
 - the command runs successfully
 - the client returns an error
 - the container id is empty

For docker rename, it covers
the cases that:
 - the command runs successfully
 - the container old name is empty
 - the container new name is empty
 - the client returns an error

Co-authored-by: Laura Brehm <laurabrehm@hey.com>
Signed-off-by: Stavros Panakakis <stavrospanakakis@gmail.com>

cli/command/container/diff_test.go

@@ -0,0 +1,93 @@
+package container
+
+import (
+	"context"
+	"io"
+	"strings"
+	"testing"
+
+	"github.com/docker/cli/internal/test"
+	"github.com/docker/docker/api/types/container"
+	"github.com/pkg/errors"
+	"gotest.tools/v3/assert"
+	is "gotest.tools/v3/assert/cmp"
+)
+
+func TestRunDiff(t *testing.T) {
+	cli := test.NewFakeCli(&fakeClient{
+		containerDiffFunc: func(
+			ctx context.Context,
+			containerID string,
+		) ([]container.FilesystemChange, error) {
+			return []container.FilesystemChange{
+				{
+					Kind: container.ChangeModify,
+					Path: "/path/to/file0",
+				},
+				{
+					Kind: container.ChangeAdd,
+					Path: "/path/to/file1",
+				},
+				{
+					Kind: container.ChangeDelete,
+					Path: "/path/to/file2",
+				},
+			}, nil
+		},
+	})
+
+	cmd := NewDiffCommand(cli)
+	cmd.SetOut(io.Discard)
+
+	cmd.SetArgs([]string{"container-id"})
+
+	err := cmd.Execute()
+	assert.NilError(t, err)
+
+	diff := strings.SplitN(cli.OutBuffer().String(), "\n", 3)
+	assert.Assert(t, is.Len(diff, 3))
+
+	file0 := strings.TrimSpace(diff[0])
+	file1 := strings.TrimSpace(diff[1])
+	file2 := strings.TrimSpace(diff[2])
+
+	assert.Check(t, is.Equal(file0, "C /path/to/file0"))
+	assert.Check(t, is.Equal(file1, "A /path/to/file1"))
+	assert.Check(t, is.Equal(file2, "D /path/to/file2"))
+}
+
+func TestRunDiffClientError(t *testing.T) {
+	clientError := errors.New("client error")
+
+	cli := test.NewFakeCli(&fakeClient{
+		containerDiffFunc: func(
+			ctx context.Context,
+			containerID string,
+		) ([]container.FilesystemChange, error) {
+			return nil, clientError
+		},
+	})
+
+	cmd := NewDiffCommand(cli)
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+
+	cmd.SetArgs([]string{"container-id"})
+
+	err := cmd.Execute()
+	assert.ErrorIs(t, err, clientError)
+}
+
+func TestRunDiffEmptyContainerError(t *testing.T) {
+	cli := test.NewFakeCli(&fakeClient{})
+
+	cmd := NewDiffCommand(cli)
+	cmd.SetOut(io.Discard)
+	cmd.SetErr(io.Discard)
+
+	containerID := ""
+	cmd.SetArgs([]string{containerID})
+
+	err := cmd.Execute()
+	assert.Error(t, err, "Container name cannot be empty")
+}