gotham-village / truthish

A Kotlin multiplatform unit testing library inspired by / similar to Google Truth.

Truthish

A testing API inspired by Google Truth but rewritten in Kotlin from the ground up, so it can be used in Kotlin multiplatform projects.

For example, you can write assertThat checks in tests like this:

import com.varabyte.truthish.*

fun isEven(num: Int) = (num % 2) == 0
fun square(num: Int) = (num * num)

@Test
fun testEvenOdd() {
    assertThat(isEven(1234)).isTrue()
    assertThat(isEven(1235)).isFalse()
}

@Test
fun testSum() {
    val nums = listOf(1, 2, 3, 4, 5)
    assertThat(nums.sum()).isEqualTo(15)
}

@Test
fun testMap() {
    assertThat(listOf(1, 2, 3, 4, 5).map { square(it) })
        .containsExactly(1, 4, 9, 16, 25)
        .inOrder()
}

@Test
fun customMessage() {
    assertWithMessage("Unexpected list size")
        .that(listOf(1, 2, 3, 4, 5)).hasSize(5)
}

@Test
fun testDivideByZeroException() {
    val ex = assertThrows<ArithmeticException> {
        10 / 0
    }
    assertThat(ex.message).isEqualTo("/ by zero")
}

You can read the Google Truth documentation for why they believe their fluent approach to assertions is both more readable and produces cleaner error messages, but let's break one of the tests above to see a specific example error message:

@Test
fun testMapButIntentionallyBroken() {
    assertThat(listOf(1, 2, 3, 4, 5).map { square(it) })
        .containsExactly(1, 4, 9, 15, 26) // <-- Ooops, messed up 16 and 25 here
        .inOrder()
}

Output:

A collection did not contain element(s)

Expected exactly all elements from: [ 1, 4, 9, 15, 26 ]
But was                           : [ 1, 4, 9, 16, 25 ]
Missing                           : [ 15, 26 ]
Extraneous                        : [ 16, 25 ]

Using Truthish in Your Project

Multiplatform

To use Truthish in your multiplatform application, declare the following dependencies:

// build.gradle.kts
// Multiplatform

repositories {
    mavenCentral()
}

kotlin {
    jvm()
    js(IR) {
        browser()
    }

    linuxX64()
    macosArm64() // Mac M1+
    macosX64() // Mac Intel
    mingwX64() // Windows
    iosX64() // iOS Intel
    iosArm64() // iOS M1+
    iosSimulatorArm64()
    android()

    sourceSets {
        val commonTest by getting {
            dependencies {
                implementation("com.varabyte.truthish:truthish:0.6.5")
            }
        }

        val jvmTest by getting {
            dependencies {
                implementation(kotlin("test"))
            }
        }

        val jsTest by getting {
            dependencies {
                implementation(kotlin("test-js"))
            }
        }
        
        // Other configurations don't seem to need a kotlin("test") dependency, nice!
    }
}

Single platform

You can also use Truthish in non-multiplatform projects as well:

JVM

// build.gradle.kts

repositories {
    mavenCentral()
}

dependencies {
    // ...

    testImplementation(kotlin("test"))
    testImplementation("com.varabyte.truthish:truthish:0.6.5")
}

Android

// build.gradle.kts

repositories {
    mavenCentral()
}

android { /* ... */ }

dependencies {
    // ...

    // If used in tests run on the host
    testImplementation("com.varabyte.truthish:truthish:0.6.5")

    // If used in tests run on the device
    androidTestImplementation("com.varabyte.truthish:truthish:0.6.5")
}