How to write a unit test

See also: Unit testing

This document demonstrates how to write a unit test for juju.

We will assume a scenario where we are creating a new provider for a cloud called “magic”, so we have a package called magic that lives at github.com/juju/juju/provider/magic with a bunch of code files, magic1.go, magic2.go, … , and we want set up a unit test for the code in file magic1.go.

Contents:

• Prepare for the test
  • Create package_test.go
  • Create <code-filename>_test.go
  • Import gocheck
  • Add a unit test suite
• Write the test
• Run the test

Prepare for the test

In the code directory (in our example, provider/magic/), create a file with the name package_test.go. This file contains mandatory contents before you can start doing any test. The exact contents will depend on whether you need a MongoDB for your tests (i.e., you use the util suite JujuConSuite) or not. Below we illustrate both.

Here is an example for the basic case where you do not need a MongoDB: We import the “testing” package from the standard library and then the gocheck package as gc. We also create a function Test that will be the entrypoint into our test suites.

// Copyright 20XX Canonical Ltd.

// Licensed under the AGPLv3, see LICENCE file for details.

package magic_test

import (

  "testing"

  gc "gopkg.in/check.v1"

)


func Test(t *testing.T) {

  gc.TestingT(t)

}

Here is an example for the basic case where you do need a MongoDB: We import the standard testing package as stdtesting and then the Juju testing package. Then we create a function Test that does the same as before (Test is a wrapper around gc.TestingT(t)) but also gives you access to a MongoDB.

// Copyright 20XX Canonical Ltd.

// Licensed under the AGPLv3, see LICENCE file for details.

package magic_test

import (

  stdtesting "testing"

  "github.com/juju/juju/testing"

)

func Test(t *stdtesting.T) {

  testing.MgoTestPackage(t)

}

Create <code-filename>_test.go

In the code directory (in our scenario, provider/magic), for each file that you want to test (in our scenario, magic1.go), create a <code-filename>_test.go (given our scenario, magic1_test.go).

Import gocheck

See also: gocheck

In magic1_test.go, import the gocheck package as gc:

import (

  gc "gopkg.in/check.v1"

)

Add a unit test suite

See also: Unit test suite

Also in magic1_test.go, add a unit test suite. A unit test suite can be as simple as an empty struct, but can also inherit complex functionality from predefined util test suites. For more see How to create a unit test suite.

Write the test

See also: Checkers

In magic1_test.go, below the test suite, start adding your unit test functions.

The process is as follows: You target some behavior (usually a function) in the code file (in our case, magic1). You then write a test for it, where the test usually follows the same Given, When, Then logic.

For example, suppose your magic1.go file defines a simple function called Sum:

func Sum(a, b int) int {
	return a + b
}

Then, in your magic1_test.go file you can write a test for it as follows (where gc.Equals is a Checker):

// GIVEN a equals 5 AND b equals 3
// WHEN a and b are summed 
// THEN we get 8
func (s *magicSuite) TestSum(c *gc.C) {
	a := 5
	b := 3

	res := magic.Sum(a,b)

	c.Assert(res, gc.Equals, 8)
}

Run the test

Finally, to run the test, do:

go test github.com/juju/juju/provider/magic/

This will run all the tests in the magic directory, including the one we just wrote.

Last updated 4 months ago.