How can I inject config properties into a unit test, using SpringBoot2, JUnit5, and Kotlin - spring

Question

My scenario:
I'm building an app that uses Kotlin and SpringBoot 2.0.3. I'm trying to write all my unit tests in JUnit5. All 3 of these are new to me, so I'm struggling a bit.
I'm using a #ConfigurationProperties class (instead of #Value) to inject values from my application.yml into my Spring context.
#Configuration
#ConfigurationProperties(prefix = "amazon.aws.s3")
class AmazonS3Config {
val s3Enabled: Boolean = false
val region: String = ""
val accessKeyId: String = ""
val secretAccessKey: String = ""
val bucketName: String = ""
}
I then have a Kotlin class that is utilizing these properties, following Kotlin/Spring best practice to define the injected class as a constructor parameter.
class VqsS3FileReader(val amazonS3Config: AmazonS3Config) : VqsFileReader {
companion object: mu.KLogging()
override fun getInputStream(filePath: String): InputStream {
val region: String = amazonS3Config.region
val accessKeyId: String = amazonS3Config.accessKeyId
val secretAccessKey: String = amazonS3Config.secretAccessKey
val bucketName: String = amazonS3Config.bucketName
logger.debug { "The configured s3Enabled is: $s3Enabled" }
logger.debug { "The configured region is: $region" }
logger.debug { "The configured accessKeyId is: $accessKeyId" }
logger.debug { "The configured secretAccessKey is: $secretAccessKey" }
logger.debug { "The configured bucketName is: $bucketName" }
val file: File? = File(filePath)
//This method is not yet implemented, just read a file from local disk for now
return file?.inputStream() ?: throw FileNotFoundException("File at $filePath is null")
}
}
I have not completed this implementation, as I'm trying to get the unit test working first. So for the moment, this method doesn't actually reach out to S3, just streams a local file.
My unit test is where I'm getting stuck. I don't know how to inject the properties from my application.yml into the test context. Since the ConfigProperty class is passed as a construction parameter, I have to pass it when I establish my service in my unit test. I've tried various solutions that don't work. I found this piece of info, which was helpful:
If Spring Boot is being used, then #ConfigurationProperties instead of #Value annotations can be used, but currently this only works with lateinit or nullable var properties (the former is recommended) since immutable classes initialized by constructors are not yet supported.
So this means I cannot use class VqsS3FileReaderTest(amazonS3Config: AmazonS3Config): TestBase() { ... } and then pass the config to my service.
This is what I have currently:
#ActiveProfiles("test")
#TestInstance(TestInstance.Lifecycle.PER_CLASS)
#ExtendWith(SpringExtension::class)
#ContextConfiguration(classes = [AmazonS3Config::class, VqsS3FileReader::class])
class VqsS3FileReaderTest(): TestBase() {
#Autowired
private lateinit var amazonS3Config: AmazonS3Config
#Autowired
private lateinit var fileReader: VqsS3FileReader
val filePath: String = "/fileio/sampleLocalFile.txt"
#Test
fun `can get input stream from a valid file path` () {
fileReader = VqsS3FileReader(amazonS3Config)
val sampleLocalFile: File? = getFile(filePath) //getFile is defined in the TestBase class, it just gets a file in my "resources" dir
if (sampleLocalFile != null) {
val inStream: InputStream = fileReader.getInputStream(sampleLocalFile.absolutePath)
val content: String = inStream.readBytes().toString(Charset.defaultCharset())
assert.that(content, startsWith("Lorem Ipsum"))
} else {
fail { "The file at $filePath was not found." }
}
}
}
With this, my test runs, and my context seems to setup properly, but the properties from my application.yml are not being injected. For my debug output, I see the following:
08:46:43.111 [main] DEBUG com.ilmn.vqs.fileio.VqsS3FileReader - The configured s3Enabled is: false
08:46:43.111 [main] DEBUG com.ilmn.vqs.fileio.VqsS3FileReader - The configured region is:
08:46:43.112 [main] DEBUG com.ilmn.vqs.fileio.VqsS3FileReader - The configured accessKeyId is:
08:46:43.112 [main] DEBUG com.ilmn.vqs.fileio.VqsS3FileReader - The configured secretAccessKey is:
08:46:43.112 [main] DEBUG com.ilmn.vqs.fileio.VqsS3FileReader - The configured bucketName is:
All empty strings, which is the default values. Not the values I have in my application.yml:
amazon.aws.s3:
s3Enabled: true
region: us-west-2
accessKeyId: unknown-at-this-time
secretAccessKey: unknown-at-this-time
bucketName: test-bucket

Answer 1

I see mistake in the following line:
#ContextConfiguration(classes = [AmazonS3Config::class, VqsS3FileReader::class])
Please put configuration classes here (instead of just beans).
Short - hot to fix test
Create class (if missing) like VqsS3Configration in the main module (e.g. in the module, where you have production code)
Create class like VqsS3TestConfigration in the same package with your tests. Content on this file:
#org.springframework.context.annotation.Configuration // mark, that this is configuration class
#org.springframework.context.annotation.Import(VqsS3Configration::class) // it references production configuration from test configuration
#org.springframework.context.annotation.ComponentScan // ask Spring to autoload all files from the package with VqsS3TestConfigration and all child packages
class VqsS3TestConfigration {
/*put test-related beans here in future*/
}
Then go to test and change declaration:
#ContextConfiguration(classes = [VqsS3TestConfigration ::class]) // we ask Spring to load configuration here
I created sample application here: https://github.com/imanushin/spring-boot2-junit5-and-kotlin-integration
Please execude line .\gradlew.bat test or gradlew.bat bootRun in the src folder. Test will check, that we able to read properties. bootRun will print auto-loaded properties
Boring theory
First of all - Spring has Configuration classes - they are needed to load and initialize other classes. Instead of Service or Comonent classes, main purpose of Configuration classes - just create services, components, etc.
If we will simplify algorithm of the Spring application load, then it will be like this:
Find Configuration classes
Read annotation of them, understand list of classes (e.g. reference tree), which should be loaded (and in addition - how they should be loaded)
Load classes with different ways:
3.1. For classes, which are annotated with #ConfigurationProperties - put configuration items here
3.2. For classes, which are annotated with #RestController - register them as rest controllers
3.N. etc...
How does Spring understand, what configuration should be loaded?
Formally is it done by Spring Boot, however I will name it as Spring
Understand several initial configurations - they can be put into the class SpringApplicationBuilder, into the test annotations (see above), into the XML context, etc. For our case we use test annotation and #ContextConfiguration attribute
Recursive get all imported configuration (e.g. Spring reads #Import annotation, then it get children, then it check their imports, etc.)
Use Spring Factories to get configuration automatically from jar
Therefore, in our case, Spring will do actions like this:
Get configuration from test annotation
Get all other configurations by recursive way
Load all classes into the contet
Start test

Answer 2

Okay, it took me all day, but I finally got my application properties to load into my unit test context. I made 2 changes:
First, I added the #Service annotation to my VqsS3FileReader service - which I had originally forgotten. Also, while I had updated my Test to not inject the AmazonS3Config via the constructor, I had neglected to update my service to do the same. So I changed
this:
class VqsS3FileReader(val amazonS3Config: AmazonS3Config) : VqsFileReader {
companion object: mu.KLogging()
...
to this:
#Service
class VqsS3FileReader : VqsFileReader {
companion object: mu.KLogging()
#Resource
private lateinit var amazonS3Config: AmazonS3Config
...
Finally, I modified my Spring annotations on my test.
from this:
#ActiveProfiles("test")
#TestInstance(TestInstance.Lifecycle.PER_CLASS)
#ExtendWith(SpringExtension::class)
#ContextConfiguration(classes = [AmazonS3Config::class, VqsS3FileReader::class])
class VqsS3FileReaderTest(): TestBase() {
...
to this:
#ActiveProfiles("test")
#SpringBootTest
#ComponentScan("com.ilmn.*")
#TestInstance(TestInstance.Lifecycle.PER_CLASS)
#ExtendWith(SpringExtension::class)
#EnableAutoConfiguration
#SpringJUnitConfig(SpringBootContextLoader::class)
class VqsS3FileReaderTest(): TestBase() {
...
It seems like I have an unordinary amount of annotations on my test now... so I will be looking carefully at what each of them really do, and see if I can reduce it. But at least my properties are being injected into my test context now.