diff --git a/builder/azure/chroot/step_mount_device_test.go b/builder/azure/chroot/step_mount_device_test.go
new file mode 100644
index 000000000..3d2fa52c6
--- /dev/null
+++ b/builder/azure/chroot/step_mount_device_test.go
@@ -0,0 +1,66 @@
+package chroot
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/hashicorp/packer/common"
+	"github.com/hashicorp/packer/helper/multistep"
+)
+
+func TestStepMountDevice_Run(t *testing.T) {
+	mountPath, err := ioutil.TempDir("", "stepmountdevicetest")
+	if err != nil {
+		t.Errorf("Unable to create a temporary directory: %q", err)
+	}
+	step := &StepMountDevice{
+		MountOptions:   []string{"foo"},
+		MountPartition: "42",
+		MountPath:      mountPath,
+	}
+
+	var gotCommand string
+	var wrapper common.CommandWrapper
+	wrapper = func(ran string) (string, error) {
+		gotCommand = ran
+		return "", nil
+	}
+
+	state := new(multistep.BasicStateBag)
+	state.Put("wrappedCommand", wrapper)
+	state.Put("device", "/dev/quux")
+
+	ui, getErrs := testUI()
+	state.Put("ui", ui)
+
+	var config Config
+	state.Put("config", &config)
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	got := step.Run(ctx, state)
+	if got != multistep.ActionContinue {
+		t.Errorf("Expected 'continue', but got '%v'", got)
+	}
+
+	var expectedMountDevice string
+	switch runtime.GOOS {
+	case "freebsd":
+		expectedMountDevice = "/dev/quuxp42"
+	default: // currently just Linux
+		expectedMountDevice = "/dev/quux42"
+	}
+	expectedCommand := fmt.Sprintf("mount -o foo %s %s", expectedMountDevice, mountPath)
+	if gotCommand != expectedCommand {
+		t.Errorf("Expected '%v', but got '%v'", expectedCommand, gotCommand)
+	}
+
+	os.Remove(mountPath)
+	_ = getErrs
+}