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@jota-one/drosse

Mock your backend the right way.

1.13.1
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npm

Version published: 4 years ago

Weekly downloads: 175; increased by157.35%

Maintainers: 2

Weekly downloads

Created: 4 years ago

Source

What is it ?

Drosse is the last mock server you'll ever need.

Installation

As npm dependency in your node project

Simply install it as a dev dependency of the project you want to mock.

npm install --save-dev @jota-one/drosse

Define a script in your package.json file for simpler usage

{
  "name": "my-node-project",
  "scripts": {
    "mock-server": "npx drosse-serve -r path/to/mocks-directory"
  },
  "devDependencies": {
    "@jota-one/drosse": "^1.0.0"
  }
}

As a global npm package

Install drosse globally.

npm i -g @jota-one/drosse

Run it via the serve command and your drosse folder as root via the -r param.

drosse serve -r /path/to/my/my/mocks

As a Docker image

You can use a docker image if you don't want to install nodejs runtime on your machine. Note though that you'll have to map your local folder to the container's data volume as well as the port your drosse is configured on.

Pull the docker image on your computer

docker pull jotaone/drosse

Run the container and map your mocks' path and port

docker run -v /path/to/my/mocks:/data -p 8000:8000 jotaone/drosse

Usage

You need a directory where you will store all your mocks definitions.

Create a directory anywhere in your project repository (or anywhere else).
Update the package.json script you just added in the Installation phase to target your new mocks directory.
In your mocks directory, create a routes.json file. This file will hold every single mocked route of your server.
In the same directory, you can also create a .drosserc.js file. This file allows you to configure your mock server (see below). It's optional but you will very likely need it.

Yes there are a couple of things to do yourself. But you're a developer, right? You know how to edit a JSON file or a JS file. In the upcoming releases, we will add a CLI and a UI, don't worry!

Let's focus first on these 2 files.

The routes.json file

This file is mandatory but you can customize its name in the .drosserc.js file (see below). This is where you define all the routes you want to mock. Each route is defined as a tree, with slash as separator.

:dizzy_face: Woot ? Tree ? Slash ? I just want to mock a couple of routes...

Ooook, an example worth a thousand sentences of bad explanation. Let's say you want to mock these 2 routes:

GET /api/users
GET /api/users/:id

You would create a tree in your routes.json file like this:

{
  "api": {
    "users": {
      ":id": {

      }
    }
  }
}

That's what we mean by "a tree". We consider that an API can be completely described in such a structure.

:smirk: Okay, but where do the actual mocks go ? And if have a GET AND a POST on /api/users ?

Good questions, thanks for asking.

The DROSSE object

That's where the DROSSE object comes in and saves our souls. Look at this:

{
  "api": {
    "users": {
      "DROSSE": {
        "get": {},
        "post": {}
      },
      ":id": {
        "DROSSE": {
          "get": {}
        }
      }
    }
  }
}

Everything happens inside the DROSSE object. You can insert a DROSSE object anywhere in the tree. A DROSSE object can contain HTTP verbs, like in the above example and a couple of other keys (more on these later).

:triumph: I WANT TO MOCK MY ROUTES!!! WHERE DO I PUT MY MOCKED CONTENTS???

There we go! You can mock your datas in 3 different ways:

directly inside the routes.json file, using the body key (see inline mocks).
in a static JSON file with a constrained name (see Static mocks)
in a dynamic JS file (we consider it a service) with a constrained name (see Services)

But before we move to the mock contents, let's have a look to the other stuffs you can put into the DROSSE object.

Throttling

A must have feature if you want to detect your race condition and test your lovely loading animations. You can throttle any endpoint by adding the throttle configuration object into it. Just like this:

{
  "api": {
    "users": {
      "DROSSE": {
        "get": {
          "throttle": {
            "min": 1000,
            "max": 2000
          }
        },
        "post": {}
      },
      ":id": {
        "DROSSE": {
          "get": {}
        }
      }
    }
  }
}

In the example above, the route GET /api/users will be throttled between 1 and 2 seconds (randomly chosen in the boundaries).

:cherries: Of course, you can put your throttle at any level of your routes tree and it will be inherited in all the sub routes that don't have their own throttle configuration.

{
  "api": {
    "DROSSE": {
      "throttle": {
        "min": 5000,
        "max": 10000
      }
    },
    "users": {
      "DROSSE": {
        "get": {
          "throttle": {
            "min": 1000,
            "max": 2000
          }
        },
        "post": {}
      },
      ":id": {
        "DROSSE": {
          "get": {}
        }
      }
    }
  }
}

Here all the routes under /api will be throttled between 5 and 10 seconds, except the GET /api/users that keeps its own 1-2 seconds throttling.

Proxies

In Drosse, proxies let you escape from your mock-server for a while. How does it work ?

Anywhere in your routes tree, you can define a proxy (inside the DROSSE object, like always). All the routes matching the path where your proxy is defined, but NOT matching a subsequent route will be proxied to... your proxy. Okay this sentence is really f***-up. Let's have a look to the routes.json.

{
  "api": {
    "users": {
      "DROSSE": {
        "get": {
          "throttle": {
            "min": 1000,
            "max": 2000
          }
        },
        "post": {}
      },
      ":id": {
        "DROSSE": {
          "get": {}
        }
      }
    },
    "countries": {
      "DROSSE": {
        "proxy": "https://restcountries.eu/rest/v2"
      }
    }
  }
}

In the above example, any request made on http://localhost:8000/api/countries will be done instead on https://restcountries.eu/rest/v2. The subsequent path will be applied as well.

So http://localhost:8000/api/countries/name/indonesia will be proxied to https://restcountries.eu/rest/v2/name/indonesia and return the expected result.

Of course you can still define subroutes in a proxied path. They will take precedence on the proxy. Let's change our countries block like this:

    "countries": {
      "DROSSE": {
        "proxy": "https://restcountries.eu/rest/v2"
      },
      "name": {
        "switzerland": {
          "DROSSE": {
            "get": {
              "body": {
                "name": "Switzerland",
                "description": "Best country in the World!"
              }
            }
          }
        }
      }
    }

If we call http://localhost:8000/api/countries/name/switzerland, Drosse will not proxy the request as there is a fully qualified path in our routes definition. We will then get the response defined just above and not a proxied response.

Assets

You can use the assets property in the DROSSE object to tell a path to serve only static contents. Behind the scene, it will apply the express.static middleware to this path. Let's check the following example:

{
  "content": {
    "DROSSE": {
      "assets": true
    },
    "imgs": {
      "background_*.jpg": {
        "DROSSE": {
          "assets": "content/images/background_mocked.png"
        }
      }
    }
  }
}

In this example, all calls done to /content will be done statically on the assets/content directory. For example, if you call http://localhost:8000/content/fonts/myfont.woff2, Drosse will look up for a file in [your mocks root]/assets/content/fonts/myfont.woff2 and serve it statically.

The example reveals another feature: you can rewrite the path through the assets property. If you call http://localhost:8000/content/imgs/background_whatever.jpg, Drosse will statically serve the [your mocks root]/assets/content/imgs/background_whatever.jpg file.

:fire: You can redefine this assets directory name in your .drosserc.js file (see below).

Templates

A small yet very handsome feature. Templates help you to DRY your mocked endpoints. In Drosse, a template is a simple function that takes a content and transforms it to something else. Let's take an example:

{
  "api": {
    "DROSSE": {
      "template": "response"
    },
    "products": {
      "v1": {
        "DROSSE": {
          "template": "responseV1"
        }
      }
    },
    "other": {},
    "routes": {}
  }
}

When passing a template to a node, you tell Drosse to apply this template to all endpoint results from this node path and all subnodes. Except if you redefine another template. In that case it will take precedence. In our example, any call to /api, /api/products, /api/other or /api/routes will have their response passed to the response template. But a call to /api/products/v1 will have its response passed to responseV1 template.

To use a template, you need to create a JS file, store it somewhere in your [mocks root] directory and reference it in your .drosserc.js file. Here is an example of .drosserc.js file with our 2 templates registered:

// .drosserc.js
const response = require('./templates/response')
const responseV1 = require('./templates/responseV1')

module.exports = {
  name: 'My awesome app',
  port: 8004,
  templates: { response, responseV1 }
}

Here we stored the templates in a templates directory, but you can load them from wherever you prefer. You simply need to register each template function in a templates property.

Here is how the response and responseV1 template could look like:

// response.js
module.exports = function (response) {
  return {
    version: 'v2',
    data: response
  }
}

// responseV1.js
module.exports = function (response) {
  return {
    version: 'v1',
    ...response
  }
}

You can also use these templates to perform intermediate transformations in your services (see dynamic mocks section) as they are also simple JS functions...

:fire: You need to register your templates in the .drosserc.js file only if you want to use them in the routes.json file.

Inline mocks

Let's focus first on the body key, by far the simplest but by far the less cool. If you calm down, you'll be allowed to know about the 2 other solutions. Here's how you can mock your routes with inlined mocks.

{
  "api": {
    "users": {
      "DROSSE": {
        "get": {
          "body": [
            {"id": 1, "name": "Jorinho", "premium": false},
            {"id": 2, "name": "Tadai", "premium": true}
          ]
        },
        "post": {
          "body": {"success": true}
        }
      },
      ":id": {
        "DROSSE": {
          "get": {
            "body": {"id": 1, "name": "Jorinho", "premium": false}
          }
        }
      }
    }
  }
}

The above JSON is a fully working routes.json file. If you run your mock-server with this file, you will see something like this in your console (amongst other things):

4:26:27 PM -> GET     /api/users/:id
4:26:27 PM -> GET     /api/users
4:26:27 PM -> POST    /api/users

4:26:27 PM App Example JSON app running at:
4:26:27 PM  - http://localhost:8000

Note that the routes are defined in the right order to make sure that a less precise route won't take over a more precise one. Let's create a new route to illustrate this better:

{
  "api": {
    "users": {
      "DROSSE": {
        "get": {
          "body": [
            {"id": 1, "name": "Jorinho", "premium": false},
            {"id": 2, "name": "Tadai", "premium": true}
          ]
        },
        "post": {
          "body": {"success": true}
        }
      },
      ":id": {
        "DROSSE": {
          "get": {
            "body": {"id": 1, "name": "Jorinho", "premium": false}
          }
        }
      },
      "premiums": {
        "DROSSE": {
          "get": {
            "body": [{"id": 2, "name": "Tadai"}]
          }
        }
      }
    }
  }
}

We defined a new route corresponding to this one GET /api/users/premiums. Of course, if Drosse was stupid it would define it in the same order as what we did in the routes.json file, which would make the route unreachable, because it would always be captured by the GET /api/users/:id, passing "premiums" as the :id parameter. Let's see what happens if we reload our mock server.

4:40:59 PM -> GET     /api/users/premiums
4:40:59 PM -> GET     /api/users/:id
4:40:59 PM -> GET     /api/users
4:40:59 PM -> POST    /api/users

4:40:59 PM App Example JSON app running at:
4:40:59 PM  - http://localhost:8000

:tada::tada::tada: The /premiums route was declared before the generic /:id route! Conclusion: you don't have to worry about sorting your routes when you define them inside routes.json.

:open_mouth: That's awesome! It calmed me down totally... I'm ready to know more about the 2 other ways to mock my stuffs!

Static mocks (in separated files)

As you've probably noticed, the inline mocks are not that dynamic... For instance, if we take the GET /api/users/:id route, you can call it with any value for :id, you will always get the same response. Although it can be enough for most usecases, sometimes we want a little bit more.

That's where the so-called static mocks can help you. Where you have only one mock possibility with the inline (body) mock even for parametrized routes, static mocks offer you the possibility to have a different mock for each value of each parameter!

That is why these mocks are stored in separated files. It would otherwise bloat your routes.json file.

To define a static mock, simply set the static property of your DROSSE object to true. Let's take the previous example and replace the parametrized route inline mock by a static mock:

{
  "api": {
    "users": {
      "DROSSE": {
        "get": {
          "body": [
            {"id": 1, "name": "Jorinho", "premium": false},
            {"id": 2, "name": "Tadai", "premium": true}
          ]
        },
        "post": {
          "body": {"success": true}
        }
      },
      ":id": {
        "DROSSE": {
          "get": {
            "static": true
          }
        }
      }
    }
  }
}

With such a definition, when you call GET /api/users/65?withDetails=1, drosse will look for a specific JSON file in the static subdirectory of your mocks directory.

:fire: You can redefine this static directory name in your .drosserc.js file (see below).

Drosse will look for different filenames, from the more precise to the more generic until it finds one that matches. Let's keep the above example and see which filenames will be looked for:

api.users.65.get&&withDetails=1.json
api.users.65.get.json
api.users.65.json
api.users.{id}.json

If you have a route with several path parameters, drosse will ignore them from left to right. Example, for this route:

GET /api/users/:id/posts/:type

Assuming that you have 2 types of posts, unread and read and a big quantity of users, it's more convenient to be able to define a mocked list of read posts and another mocked list of unread posts, independently of the user. For that usecase you can then create only 2 files in your static directory:

api.users.{id}.posts.read.get.json
api.users.{id}.posts.unread.get.json

:fire: If you are not sure of the precedence for a given route, just try and check the drosse console. It will log each failed attempts.

If we try to call GET /api/users/3 and we have defined the following static mocks files in our static directory.

api.users.1.json
api.users.2.json
api.users.{id}.json

1:11:29 AM App Example JSON static app running at:
1:11:29 AM  - http://localhost:8000
1:11:29 AM  - http://172.22.22.178:8000

1:11:29 AM Mocks root: /some/path/mymocks

1:17:27 AM loadStatic: tried with [/some/path/mymocks/static/api.users.3.get.json]. File not found.
1:17:27 AM loadStatic: tried with [/some/path/mymocks/static/api.users.3.json]. File not found.
1:17:27 AM loadStatic: tried with [/some/path/mymocks/static/api.users.{id}.get.json]. File not found.

You can see above that the system has first tried with the most precise api.users.3.get.json (resolved parameter + verb). Then it tries the same without verb (api.users.3.json). As it still fails, it tries without resolving the parameter, but again with the verb (api.users.{id}.get.json) and finally find a corresponding mock file with api.users.{id}.json. Of course this last one is not logged as it was found.

:bulb: if Drosse really doesn't find any file corresponding to the requested endpoint, it will give an ultimate look in the scraped static files. More on this in the endpoints scraping dedicated section (-> right here).

Services (aka dynamic mocks)

With the services, we cross some sort of line between pure mocking and an actual alternative backend for our frontend app. But sometimes it can be really useful. For example when you want to test interactivity in your app, or you don't have the backend yet because you're on a big project with separated teams and the backend will be implemented after the frontend, but you still have to deliver a working frontend at the same time as the backend, etc.

Drosse provides everything you need to implement an interactive mocked backend and let you focus on your frontend usecases.

To define a service, you have to do pretty much the same as to define a static mock. Look at this example where we replace the previous "POST users" inline mock by a service:

{
  "api": {
    "users": {
      "DROSSE": {
        "get": {
          "body": [
            {"id": 1, "name": "Jorinho", "premium": false},
            {"id": 2, "name": "Tadai", "premium": true}
          ]
        },
        "post": {
          "service": true
        }
      },
      ":id": {
        "DROSSE": {
          "get": {
            "static": true
          }
        }
      }
    }
  }
}

See ? From the routes.json file, it's quite a piece of cake :cake: !

Now of course, there is no magic (yet!) here. You have to create a file with the proper name and put it in the services subdirectory of your mocks directory.

:fire: Like for the others subdirectories, you can redefine this services directory name in your .drosserc.js file (see below).

To name your file, the rule is even simpler as for the static files. Here you just take in account the non-parameter nodes of your route path. In our case we don't have any parameter node. Our POST /api/users route will resolve into a api.users.post.js service file.

Let's just take another example to make it clear. For example for a PUT /api/users/:id/superpowers/:name the service file will be api.users.superpowers.put.js.

Now let's have a look inside these service files.

The service file

A service file must export a function that takes one object argument.

module.exports = function ({ req, res, db }) {
  // a lot of cool stuffs...
}

As you can see, the object argument gives you access to the well known req and res objects from Express. With those two and the full power of javascript, you can already do more than what you will ever need in a mock-server.

:star: The return value of your function will be passed to the associated route response (optionally modified by a template, see later).

Let's take a full example.

You call POST /api/users and pass this payload: { name: "John" }.
The function in the file services/api.users.post.js is executed.
Let's say it contains this code:

module.exports = function ({ req, res, db }) {
  const payload = req.body
  // do whatever you want with your payload
  return { added: payload.name }
}

Your call returns: { added: "John" }.
That's all folks!

:fire: But there is more! The db object gives you access to the embbedded Drosse database and its super-fancy API. This part requires a full chapter.

Drosse db API

Drosse leverages LokiJS power to allow stateful interactive mocking. But don't worry, no need for database configuration or any complicated stuffs. Basically, LokiJS is a nosql document database (a bit like mongo, but way simpler).

When you start your mock server for the first time, Drosse will create a database and store it in a mocks.json file in your [mocks root] directory. Yes! You've read it, it's a simple JSON file. You can open it in your IDE and see the content of your database. But don't modify it manually, it will probably break the database. To be precise, LokiJS is a in-memory database and it will simply dump its content every 4 seconds in the mocks.json file.

:anguished: How do I update it, then ?

LokiJS is collections-based. You can consider each collection as an array of objects, each object being a document.

To provide some contents to your database, you need to create a collections directory in your [mocks root] directory. In this directory you will define your collections. A collection can be either:

A directory that contains JSON files. These files must contain a JSON object (not an array).
A JSON files that must contain an array of objects.

In the end it's the same. Drosse will process either the directory or the big JSON file and insert it as a new collection full of documents in your database.

:fire: You can redefine the mocks.json database file and the collections directory name in your .drosserc.js file (see below).

By default, on each startup Drosse will check the collections directory and see if the collection already exists in the database. If not, it will import it. If the collection already exists, Drosse won't import it again; even if you added new files in the collection directory.

If you want a fresh database, simply delete the mocks.json file and restart Drosse.

:sweat_smile: That's a bit violent! Is there a smoother way?

You ask it, we provide.

You can define a shallowCollections key in your .drosserc.js file. It must contain an array with collection names. All the collections listed in this array will be overriden on each Drosse startup.

Identify your documents

One more thing. To make Drosse aware of how you identify each of your document, you should provide in each document a DROSSE property which contains an ids property, which itself contains a list of what you consider the document identifiers.

It can be very useful to have different identifiers for your documents. As the identifiers don't have to be unique, it's not an issue. Don't forget that Drosse is a mock server. You aim to mock a real system that lives somewhere out there. And in the real world, it happens often that the same entity is retrieved through different ways. Imagine a Project entity. It could be retrieved by its unique ID, but maybe also by a customer unique code or whatever else.

The real backend has probably different methods to fetch the project accordingly. But here we want to be fast and we don't care about all that. So we can store all the potential identifiers of a document in our DROSSE.ids array. It will look like this:

{
  "id": 1980,
  "name": "Construction of a skyscraper",
  "customer": {
    "id": 888,
    "name": "ACME corp",
    "projectCode": "SKYSCRAPER-999"
  },
  "budget": 98000000,
  "DROSSE": {
    "ids": [1980, "SKYSCRAPER-999"]
  }
}

Like this, it will be easier to find our document and we won't have to ask ourselves which identifier was sent to our service.

Reference documents

In the above example we have a customer inside a project. But what if we want to list all the customers in our app ? We could duplicate the customer informations into a customers collection, but that would mean that the customer's informations displayed in the project document are duplicated. Not good to maintain our mocks...

Here come reference documents to the rescue!

Assuming you have a customers collection with this customer document in it.

{
  "id": 888,
  "name": "ACME corp",
  "address": {
    "street": "Undefined or null 1",
    "zip": "00001",
    "town": "North Pole City"
  },
  "activity": "Secretely conquer the world by not being evil... at first."
  "DROSSE": {
    "ids": [1980, "SKYSCRAPER-999"]
  }
}

You can redefine your project like this:

{
  "id": 1980,
  "name": "Construction of a skyscraper",
  "customer": {
    "collection": "customers",
    "id": 888,
    "projectCode": "SKYSCRAPER-999"
  },
  "budget": 98000000,
  "DROSSE": {
    "ids": [1980, "SKYSCRAPER-999"]
  }
}

The company name is not duplicated anymore.

When you've fetched the project document, you can easily query the linked customer by calling the db.get.byRef() method and pass it the project.customer object. Drosse will return the corresponding customer document. You can then overwrite project.customer with this result.

API

Once your documents are stored in the database, here is how you can query them or even dynamically insert new documents programmatically. As you've maybe already read above in the dynamic mocks section, when you define a service function, it takes an object as argument and this object contains a db property. This db property exposes the whole Drosse DB API. Let's have a look to it in detail.

db.list.all(collection, cleanFields)

List all documents in a collection.

Argument	Required	Type	Description
collection	Required	String	The collection name
cleanFields	Optional	Array	A list of properties you want to exclude from each returned document