What is this

This is an example for Property based testing using fast-check. This test target is inspired from test design contest U-30 class, which is specified as a test base It is decided to be Topic Boiling Pot Requirement Specification (GOMA-1015), 7th Edition. Fast-check has Model based testing method to find test cases that fail by randomly walking the state, so I would like to try it on the repositly.

What is Model based testing?

Model based testing is the following flow.

1. Define the behavior that the test target will behave and its state in a model.
2. Compare the behavior under test target with the results predicted by the model to confirm.

Model based testing for fast-check

Model Based Testing Tutorial: What is, Tools & Example explains it has many different types of models

• Data flow
• Control flow
• Dependency graph
• Decision table
• State transition machine

In this repository, I'll try using fast-check to test state transition machines.

State transition diagram

Let's look at the state transition diagram

It seems complicated, but the point is that it has the following 6 states

OFF_CLOSE = -1,
OFF_OPEN, //0
ON_IDLE, //1
ON_OPEN, //2
ON_ACTIVE_BOIL, //3
ON_ACTIVE_KEEP, //4

and also it has the following 6 actions

• open() Opens the lid
• close() closes the lid
• fill() the water
• dispense() hot water
• reboil()
• Boil to keep boiling.

Create a model

Model, in fast-check the action is defined in the form of a Command also you can see test target on the source code Goma1015, so Let's try to use public field state,water and temperature, and Initialize it in constructor as in Goma1015.

import fc from 'fast-check'

import { Goma1015, State } from '.../src/lib/index' /src/lib/index'

/** Class Goma1015Model */
export class Goma1015Model {
  /** to manage state transition */
  public state: number
  /** to manage water volume */
  public water: number
  /** to manage temperature
  public temperature: number
  constructor() {
    This.state = State.OFF_CLOSE
    this.water = 0
    this.temperature = 25
  }
}

export type Goma1015Command = fc.Command<Goma1015Model, Goma1015>

Create actions

I want to find the unknown problem, so we leave each action executable in all states and will compare the state of each model with the actual instance.

open() open the lid condition: executable in all states

Test View point

• When open() with OFF_CLOSE/OFF_OPEN, it should transit to OFF_OPEN
• When open() with other states, it should transit to ON_OPEN
• Water inside should not change
• When you open the lid, the water temperature is going to be 25 degrees

Source

close() the lid conditions: executable in all states

Test View point

• When close() with OFF_OPEN, it should transit to OFF_CLOSE
• When close() with ON_OPEN, it should transit to ON_IDLE or ON_ACTIVE_BOIL
• When the amount of water is 10 ml or more, it should transit to ON_ACTIVE_BOIL
  • After 1 second, the temperature must be above 25
• When the amount of water is less than 10 ml, it should transit to ON_IDLE
• Water inside should not change

Source

fill() fill with water condition: executable in all states

Test View point

• It should raise an error except OFF_OPEN state or ON_OPEN state
• If the water overflows, it should raise an error.
• When water is put in with OFF_OPEN state or ON_OPEN state .can water accumulate in the pot properly?

Source

dispense() press the "dispense" button condition: executable in all states

Test View point

• It should raise an error except ON_IDLE state or ON_ACTIVE_KEEP state- If the amount of water is less than 10 ml as a result of water dispensing with ON_ACTIVE_KEEP, it should transit to ON_IDLE or
• If you press the dispense button in a state ON_IDLE or ON_ACTIVE_KEEP, hot water and water from the pot will be dispensed with collect amount.

Source

reboil() Press reboil button Operation condition: executable in all states

Test View point

• It should raise an error except ON_ACTIVE_KEEP state
• If the reboil() button is pressed in the ON_ACTIVE_KEEP state, it goes to ON_ACTIVE_BOIL state.
• Water inside should not change.

Source

boil to keep Wait until boiling. Condition: executable only during boiling state (not user input)

Test View point

• After 1 second, the temperature must be above 25
• When enough time has passed, the water temperature reaches 100 degrees and it should transit to ON_ACTIVE_KEEP.
• Water inside should not change.

Source

Launch

You can see the actual state transition like this.

fast-check is testing a lot of different conditions.

I've made 10,000 state transitions and they've all passed!

Conclusion.

The actual Goma1015 has more functionality like a timer, multiple heat retention functions, and more, so the condition is more complicated. This repository created as bottom-up style as much as possible, step by step. I would like to create UI for that as an other repository. Anyway I'm so happy to try out the model-based testing with fast-check. and any pull requests are welcomed. That's all