Added test for composite()

test/composite.js

@@ -0,0 +1,20 @@
+
+var assert = require('assert')
+
+module.exports = function (gm, dir, finish, GM) {
+  gm.source = __dirname + '/fixtures/compare_1.png';
+  var a = gm.composite(__dirname + '/fixtures/favicon.png')
+
+  var args = a.args();
+  assert.equal('composite', args[0]);
+  assert.equal(__dirname + '/fixtures/favicon.png', args[1]);
+  assert.equal(__dirname + '/fixtures/compare_1.png', args[2]);
+
+  if (!GM.integration)
+    return finish();
+
+  a 
+  .write(dir + '/composite.png', function(err) {
+    finish(err);
+  });
+}