diff --git a/internal/operator/lifecycle_test.go b/internal/operator/lifecycle_test.go
index e916095..43c0e05 100644
--- a/internal/operator/lifecycle_test.go
+++ b/internal/operator/lifecycle_test.go
@@ -91,3 +91,259 @@ func TestEnvFromContainer(t *testing.T) {
 		})
 	}
 }
+
+func TestInjectPluginVolumeMount(t *testing.T) {
+	testCases := []struct {
+		desc              string
+		mainContainerName string
+		spec              corev1.PodSpec
+		wantVolume        bool
+		wantMount         bool
+	}{
+		{
+			desc:              "injects volume and mount into main container",
+			mainContainerName: "postgres",
+			spec: corev1.PodSpec{
+				Containers: []corev1.Container{
+					{
+						Name: "postgres",
+					},
+				},
+			},
+			wantVolume: true,
+			wantMount:  true,
+		},
+		{
+			desc:              "does not mount volume on non-main containers",
+			mainContainerName: "postgres",
+			spec: corev1.PodSpec{
+				Containers: []corev1.Container{
+					{
+						Name: "sidecar",
+					},
+					{
+						Name: "postgres",
+					},
+				},
+			},
+			wantVolume: true,
+			wantMount:  true,
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			injectPluginVolumeMount(&test.spec, test.mainContainerName)
+
+			// Assert volume exists
+			var foundVolume *corev1.Volume
+			for i := range test.spec.Volumes {
+				if test.spec.Volumes[i].Name == "plugins" {
+					foundVolume = &test.spec.Volumes[i]
+					break
+				}
+			}
+
+			if test.wantVolume && foundVolume == nil {
+				t.Fatalf("expected plugins volume to be injected")
+			}
+
+			// check volume mount is only on main container
+			for _, c := range test.spec.Containers {
+				hasMount := false
+				for _, m := range c.VolumeMounts {
+					if m.Name == "plugins" && m.MountPath == "/plugins" {
+						hasMount = true
+					}
+				}
+
+				if c.Name == test.mainContainerName && !hasMount {
+					t.Errorf("expected plugins volume mount on main container %q", c.Name)
+				}
+
+				if c.Name != test.mainContainerName && hasMount {
+					t.Errorf("did not expect plugins volume mount on non-main container %q", c.Name)
+				}
+			}
+		})
+	}
+}
+
+func TestEnsureVolume(t *testing.T) {
+	testCases := []struct {
+		desc       string
+		existing   []corev1.Volume
+		input      corev1.Volume
+		wantLen    int
+		wantVolume corev1.Volume
+	}{
+		{
+			desc:     "add volume when not present",
+			existing: []corev1.Volume{},
+			input: corev1.Volume{
+				Name: "plugins",
+				VolumeSource: corev1.VolumeSource{
+					EmptyDir: &corev1.EmptyDirVolumeSource{},
+				},
+			},
+			wantLen: 1,
+			wantVolume: corev1.Volume{
+				Name: "plugins",
+				VolumeSource: corev1.VolumeSource{
+					EmptyDir: &corev1.EmptyDirVolumeSource{},
+				},
+			},
+		},
+		{
+			desc: "update existing volume",
+			existing: []corev1.Volume{
+				{
+					Name: "plugins",
+					VolumeSource: corev1.VolumeSource{
+						HostPath: &corev1.HostPathVolumeSource{
+							Path: "/old",
+						},
+					},
+				},
+			},
+			input: corev1.Volume{
+				Name: "plugins",
+				VolumeSource: corev1.VolumeSource{
+					EmptyDir: &corev1.EmptyDirVolumeSource{},
+				},
+			},
+			wantLen: 1,
+			wantVolume: corev1.Volume{
+				Name: "plugins",
+				VolumeSource: corev1.VolumeSource{
+					EmptyDir: &corev1.EmptyDirVolumeSource{},
+				},
+			},
+		},
+		{
+			desc: "keep other volumes intact",
+			existing: []corev1.Volume{
+				{
+					Name: "data",
+				},
+			},
+			input: corev1.Volume{
+				Name: "plugins",
+			},
+			wantLen: 2,
+			wantVolume: corev1.Volume{
+				Name: "plugins",
+			},
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			result := ensureVolume(test.existing, test.input)
+
+			if len(result) != test.wantLen {
+				t.Fatalf("expected %d volumes, got %d", test.wantLen, len(result))
+			}
+
+			var found *corev1.Volume
+			for i := range result {
+				if result[i].Name == test.input.Name {
+					found = &result[i]
+					break
+				}
+			}
+
+			if found == nil {
+				t.Fatalf("expected volume %q to be present", test.input.Name)
+			}
+
+			if !reflect.DeepEqual(*found, test.wantVolume) {
+				t.Errorf("volume mismatch want: %v, got:  %v", test.wantVolume, *found)
+			}
+		})
+	}
+}
+
+func TestAddVolumeMountsFromContainer(t *testing.T) {
+	testCases := []struct {
+		desc       string
+		target     corev1.Container
+		sourceName string
+		containers []corev1.Container
+		wantErr    bool
+		wantMounts []corev1.VolumeMount
+	}{
+		{
+			desc:       "add mounts from source container",
+			target:     corev1.Container{Name: "target"},
+			sourceName: "source",
+			containers: []corev1.Container{
+				{
+					Name: "source",
+					VolumeMounts: []corev1.VolumeMount{
+						{Name: "vol1", MountPath: "/mnt/vol1"},
+						{Name: "vol2", MountPath: "/mnt/vol2"},
+					},
+				},
+			},
+			wantErr: false,
+			wantMounts: []corev1.VolumeMount{
+				{Name: "vol1", MountPath: "/mnt/vol1"},
+				{Name: "vol2", MountPath: "/mnt/vol2"},
+			},
+		},
+		{
+			desc:       "return error when source container not found",
+			target:     corev1.Container{Name: "target"},
+			sourceName: "nonexistent",
+			containers: []corev1.Container{
+				{Name: "other"},
+			},
+			wantErr:    true,
+			wantMounts: nil,
+		},
+		{
+			desc: "append mounts to existing ones",
+			target: corev1.Container{
+				Name: "target",
+				VolumeMounts: []corev1.VolumeMount{
+					{Name: "existing", MountPath: "/mnt/existing"},
+				},
+			},
+			sourceName: "source",
+			containers: []corev1.Container{
+				{
+					Name: "source",
+					VolumeMounts: []corev1.VolumeMount{
+						{Name: "new", MountPath: "/mnt/new"},
+					},
+				},
+			},
+			wantErr: false,
+			wantMounts: []corev1.VolumeMount{
+				{Name: "existing", MountPath: "/mnt/existing"},
+				{Name: "new", MountPath: "/mnt/new"},
+			},
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.desc, func(t *testing.T) {
+			err := addVolumeMountsFromContainer(&test.target, test.sourceName, test.containers)
+			if test.wantErr && err == nil {
+				t.Fatalf("expected error but got nil")
+			}
+			if !test.wantErr && err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			if !reflect.DeepEqual(test.target.VolumeMounts, test.wantMounts) {
+				t.Errorf(
+					"volume mounts mismatch want: %v, got: %v",
+					test.wantMounts,
+					test.target.VolumeMounts,
+				)
+			}
+		})
+	}
+}