By Alvin Alexander. Last updated: August 5, 2021
In the process of writing the Scala Cookbook for Scala 3 (#ad), there were days when it was hard to find a working testing framework. As a result, I decided to write my own Scala 3 testing framework. Calling it a framework is a bit of a joke, as it’s only about 88 lines of source code. I named that library SimpleTest, and you can find it at github.com/alvinj/SimpleTest.
So I can easily find the source code later, I’m putting Version 0.3 of the source code here:
package com.alvinalexander.simpletest
/**
* All of the source code in this file is distributed under the
* GNU General Public License v3.0. See the LICENSE file in this
* project, or https://choosealicense.com/licenses/gpl-3.0 for
* more details.
*
* Created by Alvin J. Alexander, https://alvinalexander.com
*/
package support {
val AnsiRed = "\u001B[31m"
val AnsiGreen = "\u001B[32m"
val AnsiYellow = "\u001B[33m"
val AnsiReset = "\u001B[0m"
def printRed(s: String) = println(s"${AnsiRed}${s}${AnsiReset}")
def printGreen(s: String) = println(s"${AnsiGreen}${s}${AnsiReset}")
def printYellow(s: String) = println(s"${AnsiYellow}${s}${AnsiReset}")
}
import support._
object SimpleTest:
private def _True(
blockOfTestCode: => Boolean,
trueString: String,
falseString: String
): Unit =
if blockOfTestCode then
printGreen(trueString)
else
printRed(falseString)
end if
/**
* Assert that an expression is true.
* @param blockOfTestCode The expression to test.
* @param num The test number.
*/
def True(blockOfTestCode: => Boolean, num: Int): Unit =
_True(
blockOfTestCode,
s"(true) test $num",
s"(false) test $num"
)
/**
* Assert that an expression is true.
* @param blockOfTestCode The expression to test.
* @param desc The test description.
*/
def True(blockOfTestCode: => Boolean, desc: String): Unit =
_True(
blockOfTestCode,
s"(true) $desc",
s"(false) $desc"
)
private def _False(
blockOfTestCode: => Boolean,
trueString: String,
falseString: String
): Unit =
if blockOfTestCode == false then
printGreen(trueString)
else
printRed(falseString)
end if
/**
* Assert that an expression is false.
* @param blockOfTestCode The expression to test.
* @param num The test number.
*/
def False(blockOfTestCode: => Boolean, num: Int): Unit =
_False(
blockOfTestCode,
s"(true) test $num",
s"(false) test $num"
)
/**
* Assert that an expression is false.
* @param blockOfTestCode The expression to test.
* @param desc The test description.
*/
def False(blockOfTestCode: => Boolean, desc: String): Unit =
_False(
blockOfTestCode,
s"(true) $desc",
s"(false) $desc"
)
/**
* Assert that the two given values are equal (`==`).
* @param expected The expected result.
* @param actual The actual result.
* @param desc A description of the test.
*/
def Equals(expected: Any, actual: Any, desc: String): Unit =
if expected == actual then
printGreen(s"(true) $desc")
else
printRed(s"(false) EXPECTED: ($expected), ACTUAL: ($actual), DESC: $desc")
end if
def Todo(desc: String): Unit =
printYellow(s"TODO: $desc")
/**
* This is a different approach so you don’t have to supply
* a description. Just let this object keep track of the
* test numbers for you.
*/
private var testCount = 0
def True(blockOfTestCode: => Boolean): Unit =
testCount += 1
if blockOfTestCode then
printGreen(s"(true) test $testCount")
else
printRed(s"(false) test $testCount")
end if
def False(blockOfTestCode: => Boolean): Unit =
testCount += 1
if blockOfTestCode == false then
printGreen(s"(true) test $testCount")
else
printRed(s"(false) test $testCount")
end if
/**
* Assert that the two given values are equal (`==`).
* @param expected The expected result.
* @param actual The actual result.
*/
def Equals(expected: Any, actual: Any): Unit =
//TODO decide on what output you want to see here
testCount += 1
if expected == actual then
printGreen(s"(true) EXPECTED: ($expected), ACTUAL: ($actual)")
else
printRed(s"(false) EXPECTED: ($expected), ACTUAL: ($actual)")
end if
end SimpleTest
That code can use some refactoring, but (a) it did what I needed it to, and (b) writing the Scala Cookbook was the highest priority at the time I wrote this code. I know my OKRs. ;)
Demonstration code
Also for myself, this code shows how to use that library in Scala 3:
package tests
import com.alvinalexander.simpletest.SimpleTest._
@main def tests =
// run tests and give them descriptions
True(1 == 1, "1 == 1 (expecting green)")
True(1 == 2, "1 == 2 (expecting red)")
False(1 == 2, "1 == 2 (expecting green)")
False(1 == 1, "1 == 1 (expecting red)")
Equals(1, 1, "i expect green")
Equals(1, 2, "i expect red here")
Todo("don’t forget to test 2 == 3")
// run tests but only give them numbers
True(1 == 1, 1)
True(2 == 2, 2)
True(3 == 3, 3)
False(1 == 7, 4)
False(1 == 8, 5)
False(6 == 60, 6)
// numbering is too much work, just let the object
// keep track of the test numbers
True(1 == 1)
False(1 == 2)
Equals(1, 1)
package t1 {
import com.alvinalexander.simpletest.SimpleTest._
@main def tests =
// use `True` to assert that an expression is true
True(1 == 1, "1 == 1 (expecting green)")
True(1 == 2, "1 == 2 (expecting red)")
// use `False` to assert that an expression is false
False(1 == 2, "1 == 2 (expecting green)")
False(1 == 1, "1 == 1 (expecting red)")
// use `Equals` to assert that two objects are `==`
Equals(1, 1, "i expect green")
Equals(1, 2, "i expect red here")
// in case you want to note tests that you intend to run
Todo("don’t forget to test 2 == 3")
// just run some tests and simpletest will keep track of
// the test numbers for you
True(1 == 1)
False(1 == 2)
Equals(1, 1)
}
If you need a real testing framework for Scala 3, I recommend something like ScalaTest or mUnit, but for the purposes of the Scala Cookbook I needed something that worked every day, so I wrote this.
