diff --git a/pkg/gitkustomizediff/run_test.go b/pkg/gitkustomizediff/run_test.go
new file mode 100644
index 0000000..e32ae21
--- /dev/null
+++ b/pkg/gitkustomizediff/run_test.go
@@ -0,0 +1,64 @@
+/*
+Copyright 2021 Daisuke Taniwaki.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package gitkustomizediff
+
+import (
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/dtaniwaki/git-kustomize-diff/pkg/utils"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	exampleRepoUrl = "https://github.com/dtaniwaki/git-kustomize-diff-example.git"
+)
+
+func TestRun(t *testing.T) {
+	expectedFooDiff := strings.TrimLeft(`
+@@ -5,4 +5,4 @@
+ spec:
+   containers:
+   - image: nginx:latest
+-    name: foo-modified
++    name: foo-in-branch
+`, "\n")
+	tmpGitDir, err := ioutil.TempDir("", "kustomize-diff-test-")
+	if !assert.NoError(t, err) {
+		t.FailNow()
+	}
+	defer os.RemoveAll(tmpGitDir)
+	workDir := &utils.WorkDir{
+		Dir: tmpGitDir,
+	}
+	_, _, err = workDir.RunCommand("git", "clone", exampleRepoUrl, tmpGitDir)
+	if !assert.NoError(t, err) {
+		t.FailNow()
+	}
+	diffMap, err := Run(tmpGitDir, RunOpts{
+		Base:   "origin/main",
+		Target: "origin/a-branch",
+		Debug:  true,
+	})
+	if !assert.NoError(t, err) {
+		t.FailNow()
+	}
+	assert.Equal(t, []string{"foo"}, diffMap.Dirs())
+	assert.Equal(t, expectedFooDiff, diffMap.Results["foo"].ToString())
+}