Add explanatory message for missing or extra newlines.

build.gradle.kts

@@ -10,7 +10,7 @@ plugins {
     java
     `maven-publish`
 
-    id("org.jmailen.kotlinter") version "3.4.4"
+    id("org.jmailen.kotlinter") version "3.4.5"
     checkstyle
     id("com.github.sherter.google-java-format") version "0.9"
 

src/main/kotlin/Submission.kt

@@ -183,7 +183,7 @@ class Submission(val solution: Solution, val submission: Class<*>, private val s
         } ?: defaultVerify(result)
     }
 
-    @Suppress("ComplexMethod")
+    @Suppress("ComplexMethod", "LongMethod")
     private fun defaultVerify(result: TestResult<*, *>) {
         val solution = result.solution
         val submission = result.submission
@@ -197,9 +197,31 @@ class Submission(val solution: Solution, val submission: Class<*>, private val s
         }
         if ((strictOutput || solution.stdout.isNotBlank()) && solution.stdout != submission.stdout) {
             result.differs.add(TestResult.Differs.STDOUT)
+            if (solution.stdout == submission.stdout + "\n") {
+                result.message = if (result.submissionIsKotlin) {
+                    "Output is missing a newline, maybe use println instead of print?"
+                } else {
+                    "Output is missing a newline, maybe use System.out.println instead of System.out.print?"
+                }
+            }
+            if (solution.stdout + "\n" == submission.stdout) {
+                result.message = if (result.submissionIsKotlin) {
+                    "Output has an extra newline, maybe use print instead of println?"
+                } else {
+                    "Output has an extra newline, maybe use System.out.print instead of System.out.println?"
+                }
+            }
         }
         if ((strictOutput || solution.stderr.isNotBlank()) && solution.stderr != submission.stderr) {
             result.differs.add(TestResult.Differs.STDERR)
+            if (solution.stdout == submission.stdout + "\n") {
+                result.message =
+                    "Error output is missing a newline, maybe use System.err.println instead of System.err.print?"
+            }
+            if (solution.stdout + "\n" == submission.stdout) {
+                result.message =
+                    "Error output has an extra newline, maybe use System.err.print instead of System.err.println?"
+            }
         }
 
         if (result.type == TestResult.Type.METHOD) {

src/main/resources/edu.illinois.cs.cs125.jenisol.core.version

@@ -1 +1 @@
-version=2021.6.0
+version=2021.6.1

src/test/java/edu/illinois/cs/cs125/jenisol/core/TestJavaExamples.kt

@@ -271,6 +271,9 @@ class TestJavaExamples : StringSpec(
         examples.java.noreceiver.twostringequality.Correct::class.java.also {
             "${it.testName()}" { it.test() }
         }
+        examples.java.noreceiver.printvprintln.Correct::class.java.also {
+            "${it.testName()}" { it.test() }
+        }
         examples.java.receiver.timeouttest.Correct::class.java.also {
             "${it.testName()}" {
                 val runnable = object : Runnable {

src/test/java/examples/java/noreceiver/printvprintln/Correct.java

@@ -0,0 +1,7 @@
+package examples.java.noreceiver.printvprintln;
+
+public class Correct {
+  public static void run() {
+    System.out.println("It");
+  }
+}

src/test/java/examples/java/noreceiver/printvprintln/Incorrect0.java

@@ -0,0 +1,7 @@
+package examples.java.noreceiver.printvprintln;
+
+public class Incorrect0 {
+  public static void run() {
+    System.out.print("It");
+  }
+}