Removed original app example. Added a few more tests to shunting yard…

… algorithm.

src/main/java/shoe/example/firstproject/ShuntingYardAlgorithm.java

@@ -1,7 +1,11 @@
 package shoe.example.firstproject;
 
+
 public class ShuntingYardAlgorithm {
     public String translate(String infixExpression) {
-        return infixExpression != null ? infixExpression : "";
+        String result = infixExpression != null ? infixExpression : "";
+        if(!result.matches("\\d*"))
+            throw new IllegalArgumentException("Badly formed expression");
+        return result;
     }
 }

src/test/java/shoe/example/firstproject/ShuntingYardAlgorithmTest.java

@@ -31,4 +31,9 @@ public void shouldReturnNumberUnchanged() {
         String result = shuntingYardAlgorithm.translate("45");
         assertThat(result, is("45"));
     }
+
+    @Test(expected=RuntimeException.class)
+    public void shouldRejectOperatorOnly() {
+        shuntingYardAlgorithm.translate("+");
+    }
 }