I have a small program, kind of like a collection ...

# getting-started

[Jebus_Chris]

I have a small program, kind of like a collection of scripts, and I need to have a different config for when I run it normally vs when I run unit tests. Is there a way create a global config so that when I run the script it loads and uses the real config file and when I run the test it loads and uses a test config file? I know every script and test could start by creating a new config, but that seems a bit much 🤔

[Adam S]

anything is possible! But I suspect that’s not a useful answer. You’ll have to provide more details, show a bit of code, demonstrate a ‘bad’ solution that you want to improve, etc…

[Jebus_Chris]

It’s kind of like how spring (🤮) can easily use different application.yml files
Test:

internal class CSVDataProviderTest {

    private val csvDataProvider = CSVDataProvider(TestConfig.config.csv.path)

    @Test
    fun getAllData() {
        val data = csvDataProvider.getData("ABC")
        assertEquals(10, data.size)
    }

Config

data class Database(val host: String, val port: Int, val user: String, val pass: String)
data class CSV(val path: String)
data class Config(val env: String, val database: Database,  val csv: CSV)

class TestConfig {

    companion object {
        val config = ConfigLoaderBuilder.default()
            .addResourceSource("/test-config.yml")
            .build()
            .loadConfigOrThrow<Config>()
    }

} // Uses hoplite, just parses a file into some data classes

[Jebus_Chris]

Same thing would apply for the ‘real’ code, a Config class with a new “real-config.yml” file. Would make more sense to me if I just had one Config class (either singleton or normal object blob thinking upside down)

[Adam S]

so I presume you have some ‘service’ class that you want to test, called CSVDataProvider

you could add a property with a default value in the constructor?

class CSVDataProvider(
  val config: Config = loadConfig() // load using Hoplite
)

then in tests you can manually create a Config instance, and pass it into the constructor

@Test
fun blah() {
  val testConfig = Config(...)

  val csvDataProvider = CsvDataProvider(config = testConfig)
}

[Adam S]

or you could decide on an environment variable that describes the location of the config file

MY_PROJECT_CONFIG_FILE_LOCATION=/Users/me/my-project/config.yml

then tell Hoplite to try and load that config, if the property is defined. In tests you could override the environment variable, and set it to a new location. This would be a little more fragile - it might be possible for two tests to accidentally overwrite the environment variable

[Jebus_Chris]

Hmm, yeah some sort of environment variable. Can’t think of any other way to dynamically set the config file name

[Jebus_Chris]

First way might be best, it’s an extra line of code but it’s very explicit