Add NativeCmdStepTest to test serialization

testlib/src/test/java/com/diffplug/spotless/generic/NativeCmdStepTest.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2021 DiffPlug
+ *
+ * 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 com.diffplug.spotless.generic;
+
+import static org.assertj.core.api.Assumptions.assumeThat;
+
+import java.io.File;
+import java.util.List;
+
+import com.diffplug.spotless.FormatterStep;
+import com.diffplug.spotless.ResourceHarness;
+
+import com.diffplug.spotless.StepHarnessWithFile;
+
+import org.junit.jupiter.api.Test;
+
+public class NativeCmdStepTest extends ResourceHarness {
+
+	@Test
+	public void testWithSed() {
+		File sed = new File("/usr/bin/sed");
+		assumeThat(sed).exists();
+		FormatterStep step = NativeCmdStep.create("format-native", sed, List.of("s/placeholder/replaced/g"));
+		StepHarnessWithFile.forStep(this, step)
+			.testResource("native_cmd/dirty.txt", "native_cmd/clean.txt");
+	}
+}