Fix config file generation in integration tests.

Using SpringBoot OutputCapture to capture stdout and write it to file
doesn't always work---sometimes I get Spring DEBUG messages in there
too! So I'm doing this myself to be on the safe side.

components/server/src/test/java/integration/config/ConfigFileTest.java

@@ -4,14 +4,11 @@
 import static util.spring.io.ResourceLocation.classpath;
 import static util.spring.io.ResourceLocation.filepathFromCwd;
 
-import java.io.File;
-import java.io.IOException;
-import java.io.PrintWriter;
+import java.io.*;
 
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
-import org.springframework.boot.test.OutputCapture;
 
 import util.config.ConfigProvider;
 import util.spring.io.ResourceLocation;
@@ -20,10 +17,22 @@
 
 
 public abstract class ConfigFileTest<T> {
-
-    @Rule
-    public final OutputCapture generatedConfig = new OutputCapture();
-
+
+    private static void writeStdoutToFile(File f, Runnable outWriter)
+            throws IOException {
+        FileOutputStream fileContents = new FileOutputStream(f);
+        PrintStream ps = new PrintStream(fileContents);
+        PrintStream currentStdout = System.out;
+        try {
+            System.setOut(ps);
+            outWriter.run();
+            System.out.flush();
+        } finally {
+            System.setOut(currentStdout);
+        }
+    }
+
+
     @Rule
     public final TemporaryFolder configDirUnderPwd = new TemporaryFolder(new File("./"));
 
@@ -32,23 +41,13 @@ public abstract class ConfigFileTest<T> {
     protected abstract RunnableApp getFileGenerator();
 
     protected abstract ConfigProvider<T> getFileContents();
-
-    protected String generateFile() {
-        getFileGenerator().run(null);
-
-        String fileContents = generatedConfig.toString();
-        return fileContents;
-    }
-
-    protected ResourceLocation writeFile() throws IOException {
-        String fileContents = generateFile();
-
+
+    private ResourceLocation writeFile() throws IOException {
         String fileName = getConfigProvider().getConfigFileName();
         File configFile = configDirUnderPwd.newFile(fileName);
-        PrintWriter out = new PrintWriter(configFile);
-        out.print(fileContents);
-        out.close();
-
+
+        writeStdoutToFile(configFile, () -> getFileGenerator().run(null));
+
         String configDirName = configDirUnderPwd.getRoot().getName();
         return filepathFromCwd(configDirName, fileName);
     }