diff --git a/.drone.yml b/.drone.yml
index 7e75260..33e173a 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -17,6 +17,7 @@ pipeline:
       - make lint
       - make test-vendor
       - make misspell-check
+      - make test
 
   build_linux_amd64:
     image: golang:1.10
diff --git a/.gitignore b/.gitignore
index 3f3e105..0e9c851 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,5 +13,5 @@
 
 release/
 
-coverage.out
+coverage.txt
 drone-packer
diff --git a/plugin_test.go b/plugin_test.go
new file mode 100644
index 0000000..c96ce88
--- /dev/null
+++ b/plugin_test.go
@@ -0,0 +1,63 @@
+package main
+
+import (
+	"os/exec"
+	"reflect"
+	"testing"
+)
+
+func Test_pkValidate(t *testing.T) {
+	type args struct {
+		config Config
+	}
+	tests := []struct {
+		name string
+		args args
+		want *exec.Cmd
+	}{
+		{
+			name: "default validate command",
+			args: args{
+				config: Config{
+					Template: "foo.json",
+					Actions:  []string{"validate"},
+				},
+			},
+			want: exec.Command("packer", "validate", "foo.json"),
+		},
+		{
+			name: "add vars flag",
+			args: args{
+				config: Config{
+					Template: "foo.json",
+					Actions:  []string{"validate"},
+					Vars: map[string]string{
+						"foo": "bar",
+					},
+					VarFiles: []string{"bar.json"},
+				},
+			},
+			want: exec.Command("packer", "validate", "-var-file", "bar.json", "-var", "foo=bar", "foo.json"),
+		},
+		{
+			name: "add except only color flag",
+			args: args{
+				config: Config{
+					Template:   "foo.json",
+					Actions:    []string{"validate"},
+					Except:     []string{"foo", "bar"},
+					Only:       []string{"a", "b"},
+					SyntaxOnly: true,
+				},
+			},
+			want: exec.Command("packer", "validate", "-except=foo,bar", "-only=a,b", "-syntax-only", "foo.json"),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := pkValidate(tt.args.config); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("pkValidate() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}