Adding tests

Overview

Teaching: 10 min
Exercises: 30 min

Questions

• What are unit tests?

• How are tests organized in Julia?

Objectives

• Learn to create unit tests and test-sets using the Test standard library

Unit tests

Now that Melissa has released her first package she fears that future changes will impact the existing functionality of her package. This can be prevented by adding tests to her package.

Looking at the structure of other packages Melissa figured out that tests usually go in a separate test folder next to the src folder. This should contain a runtests.jl file.

The standard library Test provides the functionality for writing tests: namely, the macros @test and @testset.

@test can be used to test a single equality, such as

using Test
@test 1 + 1 == 2

Several tests can be grouped in a test-set with a descriptive name

using Test
@testset "Test arithmetic equalities" begin
    @test 1 + 1 == 2
end

With this Melissa can run her test using the pkg mode of the REPL:

(MelissasModule) pkg> test

Test specific dependencies

Melissa needed to add Test to her package in order to run the code above, but actually Test is not needed for her package other than testing. Thus it is possible to move the Test entry in the Project.toml file from [deps] to an [extras] section and then add another entry:

[targets]
test = ["Test"]

Check out the sample project file for a complete example.

Create a test for MelissasModule

Create a test that ensures that shoot_distance returns a value that is between target - ε and target + ε.

Solution

using MelissasModule
using Test

@testset "Test hitting target" begin
    imprecise_trebuchet = Trebuchet(500.0, 0.25pi)
    environment = Environment(5, 100)
    precise_trebuchet = aim(imprecise_trebuchet, environment)
    @test 100 - 0.1 <= shoot_distance(precise_trebuchet, environment) <= 100 + 0.1
    # default ε is 0.1
end

Key Points

• Tests are important