Julia: Testing

Importance of Testing

Why testing is crucial in software development: Have working version in Git, document intended behavior of functions
Types of tests: Unit tests, integration tests, etc.

Unit Tests in Julia

Using the Test standard library.

Writing Unit Tests

Basic structure of a unit test: Valid Julia code with macro annotations (@)
Assertions: @test, @test_throws, @testset, etc.

Example: Unit Test Tutorial

Let's create a simple function and write tests for it:

The Function

function add(a, b)
    return a + b
end

Test File

Create a file named test_add.jl:

using Test
using SustainableSoftwareEngineering

@testset "Addition Tests" begin
    @test add(2, 2) == 4
    @test add(-1, 1) == 0
    @test add(0, 0) == 0
    @test_throws DomainError add("a", "b")
end

This example demonstrates basic unit testing by checking various scenarios for the add function.

Invoking the Written Tests

Running Tests Locally

Once you have written your tests, it's important to know how to run them to check if your code behaves as expected.

Using Julia's Interactive Session (REPL)

Start Julia's REPL: Open a terminal and run julia to start the interactive session.
Activate the Project: If your project has a specific environment, activate it by using using Pkg; Pkg.activate("path_to_your_project").
Run the Tests: Use Pkg.test() to run all tests in the test directory of the project.

Using the Command Line

Alternatively, you can run your tests directly from the command line without entering the REPL:

Navigate to your project directory.
Run julia --project=@. -e 'using Pkg; Pkg.test()' (@. means to search for a folder with a Project.toml btw)

This command will execute all tests defined in your project's test directory.

An example output

The above testing file would yield a successful output:

julia> include("test/runtests.jl")
# Test Summary:  | Pass  Total  Time
# Addition Tests |    4      4  0.0s

However, changing the above test file to:

using Test
using SustainableSoftwareEngineering

@testset "Addition Tests" begin
    @test add(2, 2) == 4
    @test add(-1, 1) == 0
    @test add(0, 0) == 1  # changed 🚨
    @test_throws DomainError add("a", "b")
end

would result in an error:

# Addition Tests: Test Failed at XXX/gits/nmh/SustainableSoftwareEngineering.jl/test/test_add.jl:7
#   Expression: add(0, 0) == 1
#    Evaluated: 0 == 1
#
# Stacktrace:
#  [1] macro expansion
#    @ /usr/local/Cellar/julia/1.9.3/share/julia/stdlib/v1.9/Test/src/Test.jl:478 [inlined]
#  [2] macro expansion
#    @ ~/Desktop/gits/nmh/SustainableSoftwareEngineering.jl/test/test_add.jl:7 [inlined]
#  [3] macro expansion
#    @ /usr/local/Cellar/julia/1.9.3/share/julia/stdlib/v1.9/Test/src/Test.jl:1498 [inlined]
#  [4] top-level scope
#    @ ~/Desktop/gits/nmh/SustainableSoftwareEngineering.jl/test/test_add.jl:5
# Test Summary:  | Pass  Fail  Total  Time
# Addition Tests |    3     1      4  0.8s