Respect err.showDiff, add Base reporter test (close mochajs#810)

lib/reporters/base.js

@@ -184,7 +184,7 @@ exports.list = function(failures){
     }
 
     // actual / expected diff
-    if ('string' == typeof actual && 'string' == typeof expected) {
+    if (err.showDiff && 'string' == typeof actual && 'string' == typeof expected) {
       fmt = color('error title', '  %s) %s:\n%s') + color('error stack', '\n%s\n');
       var match = message.match(/^([^:]+): expected/);
       msg = match ? '\n      ' + color('error message', match[1]) : '';

package.json

@@ -35,6 +35,7 @@
     "glob": "3.2.3"
   },
   "devDependencies": {
+    "rewire": "2.0.0",
     "should": ">= 2.0.x",
     "coffee-script": "1.2"
   },

test/reporters/base.js

@@ -0,0 +1,42 @@
+var rewire = require('rewire'),
+    util = require('util');
+
+describe('Base reporter', function () {
+  var Base, output;
+
+  beforeEach(function() {
+    Base = rewire('../../lib/reporters/base');
+    output = { log: [], error: [] };
+    Base.__set__('console', {
+      error: function() {
+        output.error.push(arguments);
+      },
+      log: function() {
+        output.log.push(arguments);
+      },
+      // allow info to be passed to original 'console' for debugging purposes
+      info: console.info
+    });
+  });
+
+  it('does not show diffs when showDiff property set', function () {
+    var err = new Error('test');
+    err.actual = "a1";
+    err.expected = "e1";
+    err.showDiff = false;
+    var test = {
+      err: err,
+      fullTitle: function() { return 'title'; }
+    };
+
+    Base.list([test]);
+
+    var errOut = output.error.map(function(lineArgs) {
+      return util.format.apply(null, lineArgs);
+    }).join('\n');
+
+    errOut.should.include('test');
+    errOut.should.not.include('actual');
+    errOut.should.not.include('expected');
+  });
+});