Reworked the engine to allow for more flexibility at tested expressions, as well as better messages from the Sensei. Also, simpler engine code.

Author: Julien Letrouit

src/main/java/engine/Assertions.java

@@ -0,0 +1,13 @@
+package engine;
+
+/**
+ * Asserts something about student's code before koan tests are run.
+ */
+public interface BeforeTestAssertion {
+    /**
+     * Validates that the structure of student code for a given Koan is correct, and display feedback using the given Printer.
+     * @param p The printer to give feedback through.
+     * @return Whether or not the assertion is successful or not.
+     */
+    boolean validate(final Printer p, final Locale locale, final Koan koan);
+}

src/main/java/engine/BeforeTestAssertion.java

@@ -3,34 +3,34 @@
 /**
  * Console text coloring.
  */
-public class Color {
+public final class Color {
     private static final String RESET = "\033[0m";
 
     private static final String RED = "\033[0;31m";
     private static final String GREEN = "\033[0;32m";
     private static final String CYAN = "\033[0;36m";
 
-    public static Local<String> red(Local<String> text) {
+    public static Localizable<String> red(final Localizable<String> text) {
         return text.map(Color::red);
     }
 
-    public static Local<String> green(Local<String> text) {
+    public static Localizable<String> green(final Localizable<String> text) {
         return text.map(Color::green);
     }
 
-    public static Local<String> cyan(Local<String> text) {
+    public static Localizable<String> cyan(final Localizable<String> text) {
         return text.map(Color::cyan);
     }
 
-    public static String red(String text) {
+    public static String red(final String text) {
         return String.format("%s%s%s", RED, text, RESET);
     }
 
-    public static String green(String text) {
+    public static String green(final String text) {
         return String.format("%s%s%s", GREEN, text, RESET);
     }
 
-    public static String cyan(String text) {
+    public static String cyan(final String text) {
         return String.format("%s%s%s", CYAN, text, RESET);
     }
 }

src/main/java/engine/Color.java

@@ -4,19 +4,19 @@
  * A functional interface offering the possibility to format a piece of feedback to the user given the koan's result. 
  */
 public interface FormatParam {
-    String format(KoanResult res);
+    String format(final KoanResult res);
 
     /**
      * Creates a FormatParam taking the stdIn input for the given index, convert it to an int, and increment it by the given increment.
      * 
      * Ex: if input 0 contains "3", then paramPlus(0, 10) will return "13".
      */
-    static FormatParam addToStdInInput(int inputIndex, int increment) { 
+    static FormatParam addToStdInInput(final int inputIndex, final int increment) { 
         return res -> 
             res.inputLine(inputIndex)
                 .map(line -> {
                     try {
-                        int value = Integer.parseInt(line);
+                        final int value = Integer.parseInt(line);
                         return  String.valueOf(value + increment);
                     } catch(NumberFormatException nfe) {
                         // Ignore
@@ -26,7 +26,7 @@ static FormatParam addToStdInInput(int inputIndex, int increment) {
                 .orElse("");
     }
 
-    static FormatParam stdInInput(int inputIndex) {
+    static FormatParam stdInInput(final int inputIndex) {
         return res -> res.inputLine(inputIndex).orElse("");
     }
 }

src/main/java/engine/ConsolePrinter.java

@@ -8,7 +8,7 @@
 import java.util.Scanner;
 
 public class Helpers {
-    private static Random rng = new Random();
+    private static final Random rng = new Random();
     private static Scanner scanner = null;
 
     static void cleanupStdInForKoan() {
@@ -25,26 +25,26 @@ public static String readLine() {
         return scanner.nextLine();
     }
 
-    static void setupRandomForKoan(long seed) {
+    static void setupRandomForKoan(final long seed) {
         rng.setSeed(seed);
     }
 
     public static double random() {
         return rng.nextDouble();
     }
 
-    static String formatSequence(Locale locale, double[] toFormat) {
+    static String formatSequence(final Locale locale, final double[] toFormat) {
         return formatSequence(
             locale,
             Arrays.stream(toFormat).mapToObj(Double::toString).toArray(String[]::new)
         );
     }
 
-    static String formatSequence(Locale locale, Object[] toFormat) {
+    static String formatSequence(final Locale locale, final Object[] toFormat) {
         if (toFormat == null || toFormat.length == 0) {
             return "";
         }
-        var result = new StringBuilder();
+        final var result = new StringBuilder();
         result.append(toFormat[0]);
 
         if (toFormat.length > 1) {
@@ -58,8 +58,8 @@ static String formatSequence(Locale locale, Object[] toFormat) {
         return result.toString();
     }
 
-    static boolean isInstantiable(Class<?> clasz) {
-        int modifiers = clasz.getModifiers();
+    static boolean isInstantiable(final Class<?> clasz) {
+        final int modifiers = clasz.getModifiers();
         return
             Modifier.isPublic(modifiers) &&
             !clasz.isInterface() &&