add deleting old results to clean

Author: PPeltola

tmc-langs-csharp/src/main/java/fi/helsinki/cs/tmc/langs/csharp/CSharpPlugin.java

@@ -143,7 +143,7 @@ public Optional<ExerciseDesc> scanExercise(Path path, String exerciseName) {
 
     @Override
     public RunResult runTests(Path path) {
-        deleteOldResults(path);
+        deleteResults(path);
 
         ProcessRunner runner = new ProcessRunner(getTestCommand(), path);
 
@@ -185,6 +185,8 @@ public Map<File, List<ValidationError>> getValidationErrors() {
 
     @Override
     public void clean(Path path) {
+        deleteResults(path);
+
         try {
             Files.walk(path).filter(Files::isDirectory).forEach(dir -> {
                 Path fileName = dir.getFileName();
@@ -205,7 +207,7 @@ public void clean(Path path) {
         }
     }
 
-    private void deleteOldResults(Path path) {
+    private void deleteResults(Path path) {
         try {
             Files.deleteIfExists(path.resolve(".tmc_test_results.json"));
         } catch (Exception e) {