Make roundtripping optional-ish.

Author: nedtwigg

Diff for: testlib/src/main/java/com/diffplug/spotless/StepHarness.java

@@ -27,8 +27,8 @@
 
 /** An api for testing a {@code FormatterStep} that doesn't depend on the File path. DO NOT ADD FILE SUPPORT TO THIS, use {@link StepHarnessWithFile} if you need that. */
 public class StepHarness extends StepHarnessBase {
-	private StepHarness(Formatter formatter) {
-		super(formatter);
+	private StepHarness(Formatter formatter, RoundTrip roundTrip) {
+		super(formatter, roundTrip);
 	}
 
 	/** Creates a harness for testing steps which don't depend on the file. */
@@ -49,7 +49,7 @@ public static StepHarness forSteps(FormatterStep... steps) {
 
 	/** Creates a harness for testing a formatter whose steps don't depend on the file. */
 	public static StepHarness forFormatter(Formatter formatter) {
-		return new StepHarness(formatter);
+		return new StepHarness(formatter, RoundTrip.ASSERT_EQUAL);
 	}
 
 	/** Asserts that the given element is transformed as expected, and that the result is idempotent. */

Diff for: testlib/src/main/java/com/diffplug/spotless/StepHarnessBase.java

@@ -20,12 +20,21 @@
 import org.assertj.core.api.Assertions;
 
 class StepHarnessBase implements AutoCloseable {
+	enum RoundTrip {
+		ASSERT_EQUAL, DONT_ASSERT_EQUAL, DONT_ROUNDTRIP
+	}
+
 	private final Formatter formatter;
 
-	protected StepHarnessBase(Formatter formatter) {
+	protected StepHarnessBase(Formatter formatter, RoundTrip roundTrip) {
 		this.formatter = Objects.requireNonNull(formatter);
+		if (roundTrip == RoundTrip.DONT_ROUNDTRIP) {
+			return;
+		}
 		Formatter roundTripped = SerializableEqualityTester.reserialize(formatter);
-		Assertions.assertThat(roundTripped).isEqualTo(formatter);
+		if (roundTrip == RoundTrip.ASSERT_EQUAL) {
+			Assertions.assertThat(roundTripped).isEqualTo(formatter);
+		}
 	}
 
 	protected Formatter formatter() {

Diff for: testlib/src/main/java/com/diffplug/spotless/StepHarnessWithFile.java

@@ -29,14 +29,14 @@
 public class StepHarnessWithFile extends StepHarnessBase {
 	private final ResourceHarness harness;
 
-	private StepHarnessWithFile(ResourceHarness harness, Formatter formatter) {
-		super(formatter);
+	private StepHarnessWithFile(ResourceHarness harness, Formatter formatter, RoundTrip roundTrip) {
+		super(formatter, roundTrip);
 		this.harness = Objects.requireNonNull(harness);
 	}
 
 	/** Creates a harness for testing steps which do depend on the file. */
 	public static StepHarnessWithFile forStep(ResourceHarness harness, FormatterStep step) {
-		return new StepHarnessWithFile(harness, Formatter.builder()
+		return forFormatter(harness, Formatter.builder()
 				.name(step.getName())
 				.encoding(StandardCharsets.UTF_8)
 				.lineEndingsPolicy(LineEnding.UNIX.createPolicy())
@@ -48,7 +48,7 @@ public static StepHarnessWithFile forStep(ResourceHarness harness, FormatterStep
 
 	/** Creates a harness for testing a formatter whose steps do depend on the file. */
 	public static StepHarnessWithFile forFormatter(ResourceHarness harness, Formatter formatter) {
-		return new StepHarnessWithFile(harness, formatter);
+		return new StepHarnessWithFile(harness, formatter, RoundTrip.ASSERT_EQUAL);
 	}
 
 	/** Asserts that the given element is transformed as expected, and that the result is idempotent. */