How do I manage unit test resources in Kotlin, such as starting/stopping a database connection or an embedded elasticsearch server?
Solution 1:
Your unit test class usually needs a few things to manage a shared resource for a group of test methods. And in Kotlin you can use @BeforeClass
and @AfterClass
not in the test class, but rather within its companion object along with the @JvmStatic
annotation.
The structure of a test class would look like:
class MyTestClass {
companion object {
init {
// things that may need to be setup before companion class member variables are instantiated
}
// variables you initialize for the class just once:
val someClassVar = initializer()
// variables you initialize for the class later in the @BeforeClass method:
lateinit var someClassLateVar: SomeResource
@BeforeClass @JvmStatic fun setup() {
// things to execute once and keep around for the class
}
@AfterClass @JvmStatic fun teardown() {
// clean up after this class, leave nothing dirty behind
}
}
// variables you initialize per instance of the test class:
val someInstanceVar = initializer()
// variables you initialize per test case later in your @Before methods:
var lateinit someInstanceLateZVar: MyType
@Before fun prepareTest() {
// things to do before each test
}
@After fun cleanupTest() {
// things to do after each test
}
@Test fun testSomething() {
// an actual test case
}
@Test fun testSomethingElse() {
// another test case
}
// ...more test cases
}
Given the above, you should read about:
- companion objects - similar to the Class object in Java, but a singleton per class that is not static
-
@JvmStatic
- an annotation that turns a companion object method into a static method on the outer class for Java interop -
lateinit
- allows avar
property to be initialized later when you have a well defined lifecycle -
Delegates.notNull()
- can be used instead oflateinit
for a property that should be set at least once before being read.
Here are fuller examples of test classes for Kotlin that manage embedded resources.
The first is copied and modified from Solr-Undertow tests, and before the test cases are run, configures and starts a Solr-Undertow server. After the tests run, it cleans up any temporary files created by the tests. It also ensures environment variables and system properties are correct before the tests are run. Between test cases it unloads any temporary loaded Solr cores. The test:
class TestServerWithPlugin {
companion object {
val workingDir = Paths.get("test-data/solr-standalone").toAbsolutePath()
val coreWithPluginDir = workingDir.resolve("plugin-test/collection1")
lateinit var server: Server
@BeforeClass @JvmStatic fun setup() {
assertTrue(coreWithPluginDir.exists(), "test core w/plugin does not exist $coreWithPluginDir")
// make sure no system properties are set that could interfere with test
resetEnvProxy()
cleanSysProps()
routeJbossLoggingToSlf4j()
cleanFiles()
val config = mapOf(...)
val configLoader = ServerConfigFromOverridesAndReference(workingDir, config) verifiedBy { loader ->
...
}
assertNotNull(System.getProperty("solr.solr.home"))
server = Server(configLoader)
val (serverStarted, message) = server.run()
if (!serverStarted) {
fail("Server not started: '$message'")
}
}
@AfterClass @JvmStatic fun teardown() {
server.shutdown()
cleanFiles()
resetEnvProxy()
cleanSysProps()
}
private fun cleanSysProps() { ... }
private fun cleanFiles() {
// don't leave any test files behind
coreWithPluginDir.resolve("data").deleteRecursively()
Files.deleteIfExists(coreWithPluginDir.resolve("core.properties"))
Files.deleteIfExists(coreWithPluginDir.resolve("core.properties.unloaded"))
}
}
val adminClient: SolrClient = HttpSolrClient("http://localhost:8983/solr/")
@Before fun prepareTest() {
// anything before each test?
}
@After fun cleanupTest() {
// make sure test cores do not bleed over between test cases
unloadCoreIfExists("tempCollection1")
unloadCoreIfExists("tempCollection2")
unloadCoreIfExists("tempCollection3")
}
private fun unloadCoreIfExists(name: String) { ... }
@Test
fun testServerLoadsPlugin() {
println("Loading core 'withplugin' from dir ${coreWithPluginDir.toString()}")
val response = CoreAdminRequest.createCore("tempCollection1", coreWithPluginDir.toString(), adminClient)
assertEquals(0, response.status)
}
// ... other test cases
}
And another starting AWS DynamoDB local as an embedded database (copied and modified slightly from Running AWS DynamoDB-local embedded). This test must hack the java.library.path
before anything else happens or local DynamoDB (using sqlite with binary libraries) won't run. Then it starts a server to share for all test classes, and cleans up temporary data between tests. The test:
class TestAccountManager {
companion object {
init {
// we need to control the "java.library.path" or sqlite cannot find its libraries
val dynLibPath = File("./src/test/dynlib/").absoluteFile
System.setProperty("java.library.path", dynLibPath.toString());
// TEST HACK: if we kill this value in the System classloader, it will be
// recreated on next access allowing java.library.path to be reset
val fieldSysPath = ClassLoader::class.java.getDeclaredField("sys_paths")
fieldSysPath.setAccessible(true)
fieldSysPath.set(null, null)
// ensure logging always goes through Slf4j
System.setProperty("org.eclipse.jetty.util.log.class", "org.eclipse.jetty.util.log.Slf4jLog")
}
private val localDbPort = 19444
private lateinit var localDb: DynamoDBProxyServer
private lateinit var dbClient: AmazonDynamoDBClient
private lateinit var dynamo: DynamoDB
@BeforeClass @JvmStatic fun setup() {
// do not use ServerRunner, it is evil and doesn't set the port correctly, also
// it resets logging to be off.
localDb = DynamoDBProxyServer(localDbPort, LocalDynamoDBServerHandler(
LocalDynamoDBRequestHandler(0, true, null, true, true), null)
)
localDb.start()
// fake credentials are required even though ignored
val auth = BasicAWSCredentials("fakeKey", "fakeSecret")
dbClient = AmazonDynamoDBClient(auth) initializedWith {
signerRegionOverride = "us-east-1"
setEndpoint("http://localhost:$localDbPort")
}
dynamo = DynamoDB(dbClient)
// create the tables once
AccountManagerSchema.createTables(dbClient)
// for debugging reference
dynamo.listTables().forEach { table ->
println(table.tableName)
}
}
@AfterClass @JvmStatic fun teardown() {
dbClient.shutdown()
localDb.stop()
}
}
val jsonMapper = jacksonObjectMapper()
val dynamoMapper: DynamoDBMapper = DynamoDBMapper(dbClient)
@Before fun prepareTest() {
// insert commonly used test data
setupStaticBillingData(dbClient)
}
@After fun cleanupTest() {
// delete anything that shouldn't survive any test case
deleteAllInTable<Account>()
deleteAllInTable<Organization>()
deleteAllInTable<Billing>()
}
private inline fun <reified T: Any> deleteAllInTable() { ... }
@Test fun testAccountJsonRoundTrip() {
val acct = Account("123", ...)
dynamoMapper.save(acct)
val item = dynamo.getTable("Accounts").getItem("id", "123")
val acctReadJson = jsonMapper.readValue<Account>(item.toJSON())
assertEquals(acct, acctReadJson)
}
// ...more test cases
}
NOTE: some parts of the examples are abbreviated with ...