Extra tests for the 'binary' exercise, as discussed in exercism/probl…

…em-specifications#95

This expands the JavaScript test for the 'binary' exercise to include
the same examples as the Ruby equivalent. The example solution has also
been updated so it passes the new tests.

binary/binary_test.spec.js

@@ -1,8 +1,11 @@
 var Binary = require('./binary');
 
 describe('binary', function() {
+  it('0 is decimal 0', function() {
+    expect(new Binary('0').toDecimal()).toEqual(0);
+  });
 
-  it('1 is decimal 1', function() {
+  xit('1 is decimal 1', function() {
     expect(new Binary('1').toDecimal()).toEqual(1);
   });
 
@@ -30,8 +33,15 @@ describe('binary', function() {
     expect(new Binary('10001101000').toDecimal()).toEqual(1128);
   });
 
-  xit('carrot is decimal 0', function() {
+  xit('00011111 is decimal 31', function() {
+    expect(new Binary('00011111').toDecimal()).toEqual(31);
+  });
+
+  xit('invalid inputs are decimal 0', function() {
     expect(new Binary('carrot').toDecimal()).toEqual(0);
+    expect(new Binary('012').toDecimal()).toEqual(0);
+    expect(new Binary('10nope').toDecimal()).toEqual(0);
+    expect(new Binary('nope10').toDecimal()).toEqual(0);
   });
 
-});
+});

binary/example.js

@@ -3,7 +3,11 @@
 module.exports = Binary;
 
 function Binary(binary) {
-  this.binary = parseInt(binary, 2);
+  if (binary.match(/^[01]*$/)) {
+    this.binary = parseInt(binary, 2);
+  } else {
+    this.binary = 0;
+  }
 }
 
 Binary.prototype.toDecimal = function () {