test the mixin + model function availability

test/Model/mixin.js

+var assert = require("assert")
+  , Model  = require("./../../lib/sequelize/model")
+
+module.exports = {
+  'mixin should be correctly added to the model': function() {
+    assert.isDefined(Model.hasOne)
+    assert.isDefined(Model.hasMany)
+    assert.isDefined(Model.belongsTo)
+  },
+  'model methods should be correctly added to the model': function() {
+    assert.isDefined(Model.drop)
+    assert.isDefined(Model.sync)
+    assert.isDefined(Model.prototype.save)
+    assert.isDefined(Model.prototype.destroy)
+  }
+}
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