Refactored some code and added unit tests

src/environment/Environment.java

@@ -13,7 +13,8 @@ public class Environment {
     private InputStream input;
     private PrintStream output;
     private PrintStream errorOutput;
-    private Runnable terminate;
+    private Runnable terminationFunction;
+    private Runnable errorTerminationFunction;
 
     private Environment() {}
 
@@ -29,8 +30,12 @@ public class Environment {
         this.errorOutput = errorOutput;
     }
 
-    public void setTerminate(Runnable terminate) {
-        this.terminate = terminate;
+    public void setTerminationFunction(Runnable terminationFunction) {
+        this.terminationFunction = terminationFunction;
+    }
+
+    public void setErrorTerminationFunction(Runnable errorTerminationFunction) {
+        this.errorTerminationFunction = errorTerminationFunction;
     }
 
     public InputStream getInput() {
@@ -49,8 +54,12 @@ public class Environment {
         return errorOutput;
     }
 
-    public void terminate() {
-        terminate.run();
+    public void terminateSuccessfully() {
+        terminationFunction.run();
+    }
+    
+    public void terminateExceptionally() {
+        errorTerminationFunction.run();
     }
 
 }

src/error/ErrorManager.java

@@ -26,7 +26,7 @@ public class ErrorManager {
         printError(lispException);
 
         if (isCritical(lispException))
-            environment.terminate();
+            environment.terminateExceptionally();
     }
 
     private void printError(LispException lispException) {

src/function/builtin/EXIT.java

@@ -1,22 +1,25 @@
 package function.builtin;
 
+import environment.Environment;
 import function.*;
 import sexpression.*;
 
 public class EXIT extends LispFunction {
 
     private ArgumentValidator argumentValidator;
+    private Environment environment;
 
     public EXIT() {
         this.argumentValidator = new ArgumentValidator("EXIT");
         this.argumentValidator.setMaximumNumberOfArguments(0);
+        this.environment = Environment.getInstance();
     }
 
     public SExpression call(Cons argumentList) {
         argumentValidator.validate(argumentList);
-        System.exit(0);
+        environment.terminateSuccessfully();
 
-        return null;
+        return Nil.getInstance();
     }
 
 }

src/function/builtin/PRINT.java

@@ -15,8 +15,9 @@ public class PRINT extends LispFunction {
         this.environment = Environment.getInstance();
     }
 
-    public SExpression call(Cons argList) {
-        SExpression argument = argList.getCar();
+    public SExpression call(Cons argumentList) {
+        argumentValidator.validate(argumentList);
+        SExpression argument = argumentList.getCar();
         environment.getOutput().println(argument);
 
         return argument;

src/interpreter/LispInterpreterBuilder.java

@@ -10,7 +10,9 @@ public interface LispInterpreterBuilder {
 
     void setErrorOutput(PrintStream errorOutputStream);
 
-    void setTerminate(Runnable terminationFunction);
+    void setTerminationFunction(Runnable terminationFunction);
+
+    void setErrorTerminationFunction(Runnable errorTerminationFunction);
 
     void useFile(String fileName);
 

src/interpreter/LispInterpreterBuilderImpl.java

@@ -33,10 +33,16 @@ public class LispInterpreterBuilderImpl implements LispInterpreterBuilder {
     }
 
     @Override
-    public void setTerminate(Runnable terminationFunction) {
-        this.environment.setTerminate(terminationFunction);
+    public void setTerminationFunction(Runnable terminationFunction) {
+        this.environment.setTerminationFunction(terminationFunction);
     }
 
+    @Override
+    public void setErrorTerminationFunction(Runnable errorTerminationFunction) {
+        this.environment.setErrorTerminationFunction(errorTerminationFunction);
+    }
+
+
     @Override
     public void useFile(String fileName) {
         this.fileName = fileName;

src/main/LispMain.java

@@ -16,7 +16,8 @@ public class LispMain {
         builder.setInput(System.in);
         builder.setOutput(System.out);
         builder.setErrorOutput(System.err);
-        builder.setTerminate(() -> System.exit(1));
+        builder.setTerminationFunction(() -> System.exit(0));
+        builder.setErrorTerminationFunction(() -> System.exit(1));
 
         if (args.length > 0)
             builder.useFile(args[0]);

test/error/ErrorManagerTester.java

@@ -18,7 +18,7 @@ public class ErrorManagerTester {
     private ByteArrayOutputStream outputStream;
 
     private ErrorManager createErrorManagerWithIndicators() {
-        Environment.getInstance().setTerminate(() -> indicatorSet.add(TERMINATED));
+        Environment.getInstance().setErrorTerminationFunction(() -> indicatorSet.add(TERMINATED));
         Environment.getInstance().setErrorOutput(new PrintStream(outputStream));
 
         return new ErrorManager();

test/function/builtin/PRINTTester.java

@@ -0,0 +1,54 @@
+package function.builtin;
+
+import static org.junit.Assert.assertEquals;
+import static testutil.TestUtilities.evaluateString;
+
+import java.io.*;
+import java.text.MessageFormat;
+
+import org.junit.*;
+
+import environment.Environment;
+import function.ArgumentValidator.*;
+
+public class PRINTTester {
+
+    private ByteArrayOutputStream outputStream;
+
+    private void assertPrinted(String expected) {
+        assertEquals(expected, outputStream.toString());
+    }
+
+    @Before
+    public void setUp() {
+        this.outputStream = new ByteArrayOutputStream();
+        Environment.getInstance().setOutput(new PrintStream(outputStream));
+    }
+
+    @Test
+    public void printStringWorks() {
+        String output = "\"Hello, world!\"";
+
+        evaluateString(MessageFormat.format("(print {0})", output));
+        assertPrinted(MessageFormat.format("{0}\n", output));
+    }
+
+    @Test
+    public void printSymbolWorks() {
+        String output = "A";
+
+        evaluateString(MessageFormat.format("(print ''{0})", output));
+        assertPrinted(MessageFormat.format("{0}\n", output));
+    }
+
+    @Test(expected = TooManyArgumentsException.class)
+    public void testPrintWithTooManyArguments() {
+        evaluateString("(print '1 '2)");
+    }
+
+    @Test(expected = TooFewArgumentsException.class)
+    public void testPrintWithTooFewArguments() {
+        evaluateString("(print)");
+    }
+
+}

test/sexpression/SExpressionTester.java

@@ -106,12 +106,12 @@ public class SExpressionTester {
 
     @Test
     public void testCarOfNilIsNil() {
-        assertEquals(Nil.getInstance().getCar(), Nil.getInstance());
+        assertEquals(Nil.getInstance(), Nil.getInstance().getCar());
     }
 
     @Test
     public void testCdrOfNilIsNil() {
-        assertEquals(Nil.getInstance().getCdr(), Nil.getInstance());
+        assertEquals(Nil.getInstance(), Nil.getInstance().getCdr());
     }
 
     @Test
@@ -119,7 +119,7 @@ public class SExpressionTester {
         Cons nil = Nil.getInstance();
         nil.setCar(new LispNumber("2"));
 
-        assertEquals(nil.getCar(), Nil.getInstance());
+        assertEquals(Nil.getInstance(), nil.getCar());
     }
 
     @Test
@@ -127,7 +127,7 @@ public class SExpressionTester {
         Cons nil = Nil.getInstance();
         nil.setCdr(new LispNumber("2"));
 
-        assertEquals(nil.getCdr(), Nil.getInstance());
+        assertEquals(Nil.getInstance(), nil.getCdr());
     }
 
     @Test
@@ -135,7 +135,7 @@ public class SExpressionTester {
         BigInteger value = new BigInteger("12");
         LispNumber number = new LispNumber(value.toString());
 
-        assertEquals(number.getValue(), value);
+        assertEquals(value, number.getValue());
     }
 
     @Test(expected = InvalidNumberException.class)
@@ -166,8 +166,8 @@ public class SExpressionTester {
 
     @Test
     public void testLispNumberConstants() {
-        assertEquals(LispNumber.ZERO.getValue(), new BigInteger("0"));
-        assertEquals(LispNumber.ONE.getValue(), new BigInteger("1"));
+        assertEquals(BigInteger.ZERO, LispNumber.ZERO.getValue());
+        assertEquals(BigInteger.ONE, LispNumber.ONE.getValue());
     }
 
 }

test/table/SymbolTableTester.java

@@ -29,21 +29,21 @@ public class SymbolTableTester {
     @Test
     public void retrieveSymbolValue() {
         symbolTable.put("symbol", Symbol.T);
-        assertEquals(symbolTable.get("symbol"), Symbol.T);
+        assertEquals(Symbol.T, symbolTable.get("symbol"));
     }
 
     @Test
     public void redefineSymbolValue() {
         symbolTable.put("symbol", Symbol.T);
         symbolTable.put("symbol", Nil.getInstance());
-        assertEquals(symbolTable.get("symbol"), Nil.getInstance());
+        assertEquals(Nil.getInstance(), symbolTable.get("symbol"));
     }
 
     @Test
     public void checkParentTableIsCorrect() {
         SymbolTable childTable = new SymbolTable(symbolTable);
 
-        assertEquals(childTable.getParent(), symbolTable);
+        assertEquals(symbolTable, childTable.getParent());
     }
 
     @Test
@@ -52,7 +52,7 @@ public class SymbolTableTester {
         SymbolTable childTable = new SymbolTable(symbolTable);
         SymbolTable parentTable = childTable.getParent();
 
-        assertEquals(parentTable.get("symbol"), Symbol.T);
+        assertEquals(Symbol.T, parentTable.get("symbol"));
     }
 
 }

test/testutil/SExpressionTypeAssertions.java

@@ -18,7 +18,7 @@ public final class SExpressionTypeAssertions {
     }
 
     public static void assertNil(SExpression sExpression) {
-        assertEquals(sExpression, Nil.getInstance());
+        assertEquals(Nil.getInstance(), sExpression);
 
         assertTrue(sExpression.atomp());
         assertFalse(sExpression.consp());