notation plugin uninstall

Signed-off-by: Patrick Zheng <[email protected]>

cmd/notation/internal/plugin/plugin_test.go

@@ -0,0 +1,25 @@
+package plugin
+
+import (
+	"context"
+	"runtime"
+	"testing"
+
+	"github.com/notaryproject/notation-go/dir"
+)
+
+func TestCheckPluginExistence(t *testing.T) {
+	dir.UserConfigDir = "testdata"
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping test on Windows")
+	}
+	exist, err := CheckPluginExistence(context.Background(), "non-exist-plugin")
+	if exist || err != nil {
+		t.Fatalf("expected exist to be false with nil err, got: %v, %s", exist, err)
+	}
+
+	exist, err = CheckPluginExistence(context.Background(), "test-plugin")
+	if !exist || err != nil {
+		t.Fatalf("expected exist to be true with nil err, got: %v, %s", exist, err)
+	}
+}