chore: Improve test failure reporting.

Author: jjjasper

boat-scaffold/src/test/java/com/backbase/oss/codegen/java/BoatSpringCodeGenTests.java

@@ -278,7 +278,8 @@ void shouldGenerateValidations(boolean useLombok, boolean bigDecimalsAsStrings)
         var compiler = new MavenProjectCompiler(BoatSpringCodeGenTests.class.getClassLoader());
         var projectDir = new File(output);
         int compilationStatus = compiler.compile(projectDir);
-        assertEquals(0, compilationStatus);
+        assertEquals(0, compilationStatus,
+                "Failed compilation. see " + projectDir.getAbsolutePath() + "/mvn.log for details");
 
         // verify
         ClassLoader projectClassLoader = compiler.getProjectClassLoader(projectDir);

boat-scaffold/src/test/java/com/backbase/oss/codegen/java/MavenProjectCompiler.java

@@ -2,6 +2,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.io.PrintStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLClassLoader;
@@ -56,9 +57,13 @@ public int compile(File projectDir) {
             System.setProperty(MavenCli.MULTIMODULE_PROJECT_DIRECTORY, projectDir.getAbsolutePath());
             String[] args = generateMavenCliArgs();
             log.debug("mvn cli args: {}", Arrays.toString(args));
-            int compilationStatus = mavenCli.doMain(args, projectDir.getAbsolutePath(), System.out, System.out);
+            log.info("Building: {}", projectDir.getName());
+            PrintStream out = new PrintStream(new File(projectDir, "mvn.log"));
+            int compilationStatus = mavenCli.doMain(args, projectDir.getAbsolutePath(), out, out);
             log.debug("compilation status={}", compilationStatus);
             return compilationStatus;
+        } catch (IOException e) {
+            throw new RuntimeException(e);
         } finally {
             if (StringUtils.isBlank(initialDir)) {
                 System.clearProperty(MavenCli.MULTIMODULE_PROJECT_DIRECTORY);