diff --git a/go.mod b/go.mod
index 662f6f9..fbb76ee 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module github.com/itchyny/mmv
 
 go 1.13
+
+require github.com/stretchr/testify v1.4.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..e863f51
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
diff --git a/mmv_test.go b/mmv_test.go
new file mode 100644
index 0000000..c06ac22
--- /dev/null
+++ b/mmv_test.go
@@ -0,0 +1,95 @@
+package mmv
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMove(t *testing.T) {
+	testCases := []struct {
+		name     string
+		files    map[string]string
+		contents map[string]string
+		expected map[string]string
+		err      error
+	}{
+		{
+			name:  "nothing",
+			files: nil,
+		},
+		{
+			name: "one file",
+			files: map[string]string{
+				"foo": "bar",
+			},
+			contents: map[string]string{
+				"foo": "0",
+			},
+			expected: map[string]string{
+				"bar": "0",
+			},
+		},
+		{
+			name: "two files",
+			files: map[string]string{
+				"foo": "qux",
+				"bar": "quxx",
+			},
+			contents: map[string]string{
+				"foo": "0",
+				"bar": "1",
+				"baz": "2",
+			},
+			expected: map[string]string{
+				"qux":  "0",
+				"quxx": "1",
+				"baz":  "2",
+			},
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			dir, err := ioutil.TempDir("", "mvv-"+tc.name+"-")
+			defer os.RemoveAll(dir)
+			require.NoError(t, os.Chdir(dir))
+			require.NoError(t, err)
+			require.NoError(t, setupFiles(tc.contents))
+			require.NoError(t, Move(tc.files))
+			assert.Equal(t, tc.expected, fileContents("."))
+		})
+	}
+}
+
+func setupFiles(contents map[string]string) error {
+	for f, cnt := range contents {
+		if err := ioutil.WriteFile(f, []byte(cnt), 0600); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func fileContents(dir string) map[string]string {
+	m := make(map[string]string)
+	fis, _ := ioutil.ReadDir(dir)
+	for _, fi := range fis {
+		if fi.IsDir() {
+			for k, v := range fileContents(filepath.Join(dir, fi.Name())) {
+				m[k] = v
+			}
+		} else {
+			path := filepath.Join(dir, fi.Name())
+			cnt, _ := ioutil.ReadFile(path)
+			m[path] = string(cnt)
+		}
+	}
+	if len(m) == 0 {
+		return nil
+	}
+	return m
+}