test(container): add unit test for volume subpath preservation (#265)

- Add a unit test to verify that `GetCreateHostConfig` preserves volume subpath in `HostConfig.Mounts`, addressing potential issues with subpath handling during container recreation.
- Add a `WithMounts` helper in `container_mock_test.go` to support mount configuration in tests.

Successful testing confirms that this fork of Watchtower honors Docker volume subpaths, including avoiding the issue described in containrrr#2017

Author: nicholas-fedor

pkg/container/container_mock_test.go

@@ -5,6 +5,7 @@ import (
 
 	dockerContainerType "github.com/docker/docker/api/types/container"
 	dockerImageType "github.com/docker/docker/api/types/image"
+	dockerMountType "github.com/docker/docker/api/types/mount"
 	dockerNetworkType "github.com/docker/docker/api/types/network"
 	dockerNat "github.com/docker/go-connections/nat"
 )
@@ -108,3 +109,9 @@ func WithNetworkSettings(
 		c.NetworkSettings.Networks = networks
 	}
 }
+
+func WithMounts(mounts []dockerMountType.Mount) MockContainerUpdate {
+	return func(c *dockerContainerType.InspectResponse, _ *dockerImageType.InspectResponse) {
+		c.HostConfig.Mounts = mounts
+	}
+}

pkg/container/container_test.go

@@ -10,6 +10,7 @@ import (
 
 	dockerContainerType "github.com/docker/docker/api/types/container"
 	dockerImageType "github.com/docker/docker/api/types/image"
+	dockerMountType "github.com/docker/docker/api/types/mount"
 	dockerNetworkType "github.com/docker/docker/api/types/network"
 	dockerNat "github.com/docker/go-connections/nat"
 
@@ -719,4 +720,36 @@ var _ = ginkgo.Describe("the container", func() {
 			})
 		})
 	})
+
+	ginkgo.Describe("GetCreateHostConfig", func() {
+		ginkgo.When("container has a volume mount with subpath", func() {
+			ginkgo.It("preserves the subpath in the host config mounts", func() {
+				volumeMount := dockerMountType.Mount{
+					Type:   dockerMountType.TypeVolume,
+					Source: "test_volume",
+					Target: "/config/nest",
+					VolumeOptions: &dockerMountType.VolumeOptions{
+						Subpath: "ha/nest",
+					},
+				}
+
+				container := MockContainer(WithMounts([]dockerMountType.Mount{volumeMount}))
+
+				hostConfig := container.GetCreateHostConfig()
+
+				gomega.Expect(hostConfig.Mounts).To(gomega.HaveLen(1), "Expected exactly one mount")
+				mount := hostConfig.Mounts[0]
+				gomega.Expect(mount.Type).
+					To(gomega.Equal(dockerMountType.TypeVolume), "Mount type should be volume")
+				gomega.Expect(mount.Source).
+					To(gomega.Equal("test_volume"), "Mount source should match")
+				gomega.Expect(mount.Target).
+					To(gomega.Equal("/config/nest"), "Mount target should match")
+				gomega.Expect(mount.VolumeOptions).
+					ToNot(gomega.BeNil(), "VolumeOptions should be set")
+				gomega.Expect(mount.VolumeOptions.Subpath).
+					To(gomega.Equal("ha/nest"), "Subpath should be preserved")
+			})
+		})
+	})
 })