test: WritableUtils to simplify tests

views-react/src/test/groovy/io/micronaut/views/react/PreactViewRenderSpec.groovy

@@ -22,10 +22,7 @@ class PreactViewRenderSpec extends Specification {
     void "views can be rendered with basic props and no request"() {
         when:
         Writable writable = renderer.render("App", TestProps.basic, null)
-        String result = new StringWriter().with {
-            writable.writeTo(it)
-            it.toString()
-        }
+        String result = WritableUtils.writableToString(writable).orElseThrow()
 
         then:
         result.contains("/static/client.preact.js")
@@ -40,10 +37,7 @@ class PreactViewRenderSpec extends Specification {
 
         when:
         Writable writable = renderer.render("App", TestProps.basic, req)
-        String result = new StringWriter().with {
-            writable.writeTo(it)
-            it.toString()
-        }
+        String result = WritableUtils.writableToString(writable).orElseThrow()
 
         then:
         result.contains("/static/client.preact.js")

views-react/src/test/groovy/io/micronaut/views/react/ReactViewRenderSpec.groovy

@@ -17,10 +17,7 @@ class ReactViewRenderSpec extends Specification {
     void "views can be rendered with basic props"() {
         when:
         Writable writable = renderer.render("App", TestProps.basic, null)
-        String result = new StringWriter().with {
-            writable.writeTo(it)
-            it.toString()
-        }
+        String result = WritableUtils.writableToString(writable).orElseThrow()
 
         then:
         result.contains("Hello there")
@@ -38,10 +35,7 @@ class ReactViewRenderSpec extends Specification {
 
         when:
         Writable writable = renderer.render("App", TestProps.basic, req)
-        String result = new StringWriter().with {
-            writable.writeTo(it)
-            it.toString()
-        }
+        String result = WritableUtils.writableToString(writable).orElseThrow()
 
         then:
         result.contains("/static/client.js")

views-react/src/test/groovy/io/micronaut/views/react/SandboxReactRenderSpec.groovy

@@ -19,10 +19,7 @@ class SandboxReactRenderSpec extends Specification {
     void "views can be rendered with sandboxing enabled"() {
         when:
         Writable writable = renderer.render("App", TestProps.basic, null)
-        String resultAsString = new StringWriter().with {
-            writable.writeTo(it)
-            it.toString()
-        }
+        String resultAsString = WritableUtils.writableToString(writable).orElseThrow()
 
         String dataJSON = resultAsString.find(~/var Micronaut = (\{[^;]+});/).replace("var Micronaut = ", "")
         def data = new JsonSlurper().parseText(dataJSON)
@@ -37,10 +34,7 @@ class SandboxReactRenderSpec extends Specification {
     void "host types are inaccessible with the sandbox enabled"() {
         when:
         Writable writable = renderer.render("App", TestProps.triggerSandbox, null)
-        new StringWriter().with {
-            writable.writeTo(it)
-            it.toString()
-        }
+        WritableUtils.writableToString(writable)
 
         then:
         def t = thrown(MessageBodyException)

views-react/src/test/java/io/micronaut/views/react/WritableUtils.java

@@ -0,0 +1,27 @@
+package io.micronaut.views.react;
+
+import io.micronaut.core.annotation.NonNull;
+import io.micronaut.core.io.Writable;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Optional;
+
+public final class WritableUtils {
+    private WritableUtils() {
+    }
+
+    @NonNull
+    public static Optional<String> writableToString(@NonNull Writable writable) {
+        if (writable == null) {
+            return Optional.empty();
+        }
+        try {
+            StringWriter stringWriter = new StringWriter();
+            writable.writeTo(stringWriter);
+            return Optional.of(stringWriter.toString());
+        } catch (IOException e) {
+            return Optional.empty();
+        }
+    }
+}