Constructor in Spring seems to be not working

Hi all,

I’m working on a Spring Boot project and I wanted to give it a go with Kotlintest.

Now I’m running into an issue where autowiring is not working.

This is the code I’m using:

SimpleTest.kt

import io.kotlintest.AbstractProjectConfig
import io.kotlintest.extensions.ProjectLevelExtension
import io.kotlintest.shouldBe
import io.kotlintest.specs.StringSpec
import io.kotlintest.spring.SpringAutowireConstructorExtension
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.stereotype.Service
import org.springframework.test.context.ContextConfiguration

data class User(val name: String)

@SpringBootApplication
class MyApp

interface UserService {
    fun getAnyUser(): User
}

@Service
class DummyUserService : UserService {
    override fun getAnyUser(): User {
        return User(name = "John Doe")
    }
}

class MyProjectConfig : AbstractProjectConfig() {
    override fun extensions(): List<ProjectLevelExtension> = listOf(SpringAutowireConstructorExtension)
}

In the same file I have three test classes

Field injection

@ContextConfiguration(classes = [(MyApp::class)])
class UserServiceTestFieldInjection : StringSpec() {

    override fun listeners() = listOf(SpringListener)

    @Autowired
    lateinit var userService: UserService

    init {
        "get a user from the service" {
            userService.getAnyUser().name shouldBe "John Doe"
        }
    }
}

This works as expected

Constructor injection with non-null constructor argument

@ContextConfiguration(classes = [(MyApp::class)])
class UserServiceTestConstructorInjection(userService: UserService) : StringSpec() {

    init {
        "get a user from the service" {
            userService.getAnyUser().name shouldBe "John Doe"
        }
    }
}

This throws an exception because it’s missing a no-arg constructor:

11:31:32.627 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - configurationParameters=LauncherConfigurationParameters []
11:31:32.646 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - uniqueId=[engine:kotlintest]
11:31:32.715 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - LauncherDiscoveryRequest [
classpathRootSelectors=[]
classpathResourceSelectors=[]
classSelectors=[com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection]
methodSelectors=[]
directorySelectors=[]
fileSelectors=[]
moduleSelectors=[]
packageSelectors=[]
uniqueIdSelectors=[]
uriSelectors=[]
engineFilters=[]
postDiscoveryFilters=[]
classnameFilters=[]
packageNameFilters=[]
]
11:31:32.882 [main] DEBUG io.kotlintest.runner.jvm.TestDiscovery - Loaded 1 classes from classnames...
11:31:33.635 [main] DEBUG io.kotlintest.runner.jvm.TestDiscovery - ...which has filtered to 1 non abstract classes
11:31:33.640 [main] DEBUG io.kotlintest.runner.jvm.TestDiscovery - 1 classes after applying discovery extensions11:31:33.700 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - configurationParameters=LauncherConfigurationParameters []
11:31:33.700 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - uniqueId=[engine:kotlintest]
11:31:33.700 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - LauncherDiscoveryRequest [
classpathRootSelectors=[]
classpathResourceSelectors=[]
classSelectors=[com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection]
methodSelectors=[]
directorySelectors=[]
fileSelectors=[]
moduleSelectors=[]
packageSelectors=[]
uniqueIdSelectors=[]
uriSelectors=[]
engineFilters=[]
postDiscoveryFilters=[]
classnameFilters=[]
packageNameFilters=[]
]
11:31:33.724 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - JUnit execution request [configurationParameters=LauncherConfigurationParameters []; rootTestDescriptor=KotlinTestEngineDescriptor: [engine:kotlintest]]
11:31:33.738 [main] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - Engine started; classes=[[class com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection]]
11:31:33.740 [main] DEBUG io.kotlintest.runner.jvm.TestEngine - Submitting 1 specs
11:31:33.745 [main] DEBUG io.kotlintest.runner.jvm.TestEngine - Waiting for spec execution service to terminate
11:31:33.777 [main] ERROR io.kotlintest.runner.jvm.TestEngine - Error during test engine run
java.lang.IllegalArgumentException: Class should have a single no-arg constructor: class com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection
	at kotlin.reflect.full.KClasses.createInstance(KClasses.kt:281)
	at io.kotlintest.runner.jvm.JvmKt.instantiateSpec(jvm.kt:12)
	at io.kotlintest.runner.jvm.TestEngine.createSpec(TestEngine.kt:99)
	at io.kotlintest.runner.jvm.TestEngine.access$createSpec(TestEngine.kt:14)
	at io.kotlintest.runner.jvm.TestEngine$submitSpec$1.run(TestEngine.kt:77)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
11:31:33.779 [main] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - Engine finished; throwable=[java.lang.IllegalArgumentException: Class should have a single no-arg constructor: class com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection]
java.lang.IllegalArgumentException: Class should have a single no-arg constructor: class com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection
	at kotlin.reflect.full.KClasses.createInstance(KClasses.kt:281)
	at io.kotlintest.runner.jvm.JvmKt.instantiateSpec(jvm.kt:12)
	at io.kotlintest.runner.jvm.TestEngine.createSpec(TestEngine.kt:99)
	at io.kotlintest.runner.jvm.TestEngine.access$createSpec(TestEngine.kt:14)
	at io.kotlintest.runner.jvm.TestEngine$submitSpec$1.run(TestEngine.kt:77)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

Process finished with exit code 255
Empty test suite.

So I figured to make the constructor argument nullable with a default null value. i.e. provide a default constructor.

Constructor injection with nullable constructor argument

@ContextConfiguration(classes = [(MyApp::class)])
class UserServiceTestConstructorInjection2(userService: UserService? = null) : StringSpec() {

    init {
        "get a user from the service" {
            userService!!.getAnyUser().name shouldBe "John Doe"
        }
    }
}

This throws a nice Kotlin.NullPointerException

11:35:02.950 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - configurationParameters=LauncherConfigurationParameters []
11:35:02.959 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - uniqueId=[engine:kotlintest]
11:35:02.984 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - LauncherDiscoveryRequest [
classpathRootSelectors=[]
classpathResourceSelectors=[]
classSelectors=[com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection2]
methodSelectors=[]
directorySelectors=[]
fileSelectors=[]
moduleSelectors=[]
packageSelectors=[]
uniqueIdSelectors=[]
uriSelectors=[]
engineFilters=[]
postDiscoveryFilters=[]
classnameFilters=[]
packageNameFilters=[]
]
11:35:03.221 [main] DEBUG io.kotlintest.runner.jvm.TestDiscovery - Loaded 1 classes from classnames...
11:35:04.121 [main] DEBUG io.kotlintest.runner.jvm.TestDiscovery - ...which has filtered to 1 non abstract classes
11:35:04.125 [main] DEBUG io.kotlintest.runner.jvm.TestDiscovery - 1 classes after applying discovery extensions11:35:04.192 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - configurationParameters=LauncherConfigurationParameters []
11:35:04.192 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - uniqueId=[engine:kotlintest]
11:35:04.193 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - LauncherDiscoveryRequest [
classpathRootSelectors=[]
classpathResourceSelectors=[]
classSelectors=[com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection2]
methodSelectors=[]
directorySelectors=[]
fileSelectors=[]
moduleSelectors=[]
packageSelectors=[]
uniqueIdSelectors=[]
uriSelectors=[]
engineFilters=[]
postDiscoveryFilters=[]
classnameFilters=[]
packageNameFilters=[]
]
11:35:04.197 [main] DEBUG io.kotlintest.runner.junit5.KotlinTestEngine - JUnit execution request [configurationParameters=LauncherConfigurationParameters []; rootTestDescriptor=KotlinTestEngineDescriptor: [engine:kotlintest]]
11:35:04.237 [main] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - Engine started; classes=[[class com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection2]]
11:35:04.239 [main] DEBUG io.kotlintest.runner.jvm.TestEngine - Submitting 1 specs
11:35:04.273 [main] DEBUG io.kotlintest.runner.jvm.TestEngine - Waiting for spec execution service to terminate
11:35:04.322 [pool-1-thread-1] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - prepareSpec [Description(parents=[], name=UserServiceTestConstructorInjection2)]11:35:04.362 [pool-2-thread-1] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - Creating test case descriptor Description(parents=[UserServiceTestConstructorInjection2], name=get a user from the service)/Test
11:35:04.364 [pool-2-thread-1] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - Notifying junit of start event [engine:kotlintest]/[spec:UserServiceTestConstructorInjection2]/[test:get a user from the service]
11:35:04.371 [pool-1-thread-1] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - completeTestCase Description(parents=[UserServiceTestConstructorInjection2], name=get a user from the service) with result TestResult(status=Error, error=kotlin.KotlinNullPointerException, reason=null, metaData={})
11:35:04.371 [pool-1-thread-1] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - completeSpec [Description(parents=[], name=UserServiceTestConstructorInjection2)]
11:35:04.374 [pool-1-thread-1] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - Notifying junit of test case completion [engine:kotlintest]/[spec:UserServiceTestConstructorInjection2]/[test:get a user from the service]=TestResult(status=Error, error=kotlin.KotlinNullPointerException, reason=null, metaData={})

kotlin.KotlinNullPointerException
	at com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection2$1.invoke(SImpleTest.kt:65)
	at com.brabantia.bw.bw6tests.UserServiceTestConstructorInjection2$1.invoke(SImpleTest.kt:61)
	at io.kotlintest.runner.jvm.TestCaseExecutor$executeTestSet$1.run(TestCaseExecutor.kt:96)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)

11:35:04.401 [pool-1-thread-1] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - Notifying junit that spec finished [engine:kotlintest]/[spec:UserServiceTestConstructorInjection2] TestExecutionResult [status = SUCCESSFUL, throwable = null]11:35:04.403 [main] DEBUG io.kotlintest.runner.junit5.JUnitTestRunnerListener - Engine finished; throwable=[null]

Process finished with exit code 255

In Maven I have the following configuration

    <properties>
        <kotlin.version>1.2.41</kotlin.version>
        <kotlintest.version>3.1.8</kotlintest.version>
    </properties>

    <dependencies>
        <!-- KOTLIN -->
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-reflect</artifactId>
        </dependency>

        <!-- SPRING -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.module</groupId>
            <artifactId>jackson-module-kotlin</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>

        <!-- SPRING TEST -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!-- TEST -->
        <dependency>
            <groupId>io.kotlintest</groupId>
            <artifactId>kotlintest-runner-junit5</artifactId>
            <version>${kotlintest.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.kotlintest</groupId>
            <artifactId>kotlintest-extensions-spring</artifactId>
            <version>${kotlintest.version}</version>
        </dependency>
    </dependencies>

  <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <artifactId>kotlin-maven-plugin</artifactId>
                <groupId>org.jetbrains.kotlin</groupId>
                <configuration>
                    <args>
                        <arg>-Xjsr305=strict</arg>
                    </args>
                    <compilerPlugins>
                        <plugin>spring</plugin>
                    </compilerPlugins>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-allopen</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <dependencies>
                    <dependency>
                        <groupId>org.junit.platform</groupId>
                        <artifactId>junit-platform-surefire-provider</artifactId>
                        <version>1.2.0</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>

Am I missing something here or is this a genuine bug?

[sksamuel]

Hi,

Did you place MyProjectConfig inside the io.kotlintest.provided package ?

[mindhaq]

As I just stumbled here, let me quote the essential part of the documentation to make this “magic” work:

To do this, create an object that is derived from AbstractProjectConfig, name this object ProjectConfig and place it in a package called io.kotlintest.provided. KotlinTest will detect it’s presence and use any configuration defined there when executing tests.

https://github.com/kotlintest/kotlintest/blob/master/doc/reference.md#project-config