Loading configuration in tests

Flinkboot allows you to load, merge, and validate YAML configurations directly within your JUnit 5 tests using Flinkboot.initialize(...).

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1. Overview

When writing unit or integration tests for your Flink applications, you often need to load and validate your application configuration objects (DTOs) without starting a full command-line application:

• Production parity: Tests execute through the exact same parsing and validation engine used in production.
• Varargs simplicity: Call Flinkboot.initialize() with zero arguments for default classpath configuration, or pass command-line options inline.
• Full option support: Test custom flags (--dry-run), CLI parameters (-threshold 100), or Flinkboot runtime options alongside your configuration files.
• Explicit scheme prefixes: Unified support for classpath:, resource:, and file: schemes via Flinkboot's Resource API.

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2. Usage examples

Loading default classpath configuration

Calling Flinkboot.initialize() without arguments automatically loads src/test/resources/job-configuration.yaml:

import io.github.sekelenao.flinkboot.core.api.Flinkboot;
import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.assertNotNull;

class ApplicationConfigTest {

    @Test
    void shouldLoadDefaultConfiguration() throws Exception {
        MyApplicationConfig config = Flinkboot.initialize()
            .configuration(MyApplicationConfig.class);

        assertNotNull(config);
    }
}

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Loading a specific configuration file

Pass -flinkboot-configurations with an explicit resource scheme prefix:

@Test
void shouldLoadSpecificConfiguration() throws Exception {
    MyApplicationConfig config = Flinkboot.initialize(
        "-flinkboot-configurations", "classpath:job-test.yaml"
    ).configuration(MyApplicationConfig.class);

    assertNotNull(config);
}

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Loading multiple merged configurations

You can pass multiple comma-separated configuration paths to test profile overrides:

@Test
void shouldLoadMultipleConfigurations() throws Exception {
    MyApplicationConfig config = Flinkboot.initialize(
        "-flinkboot-configurations",
        "classpath:config-base.yaml,classpath:config-test-env.yaml"
    ).configuration(MyApplicationConfig.class);

    assertNotNull(config);
}

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Loading files from the file system

Target external configuration files outside the classpath using the file: prefix:

@Test
void shouldLoadFromFileSystem() throws Exception {
    MyApplicationConfig config = Flinkboot.initialize(
        "-flinkboot-configurations", "file:/etc/flinkboot/my-config.yaml"
    ).configuration(MyApplicationConfig.class);

    assertNotNull(config);
}

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Testing with flags and CLI parameters

You can pass custom flags and parameters inline:

@Test
void shouldLoadConfigurationWithOptions() throws Exception {
    Flinkboot boot = Flinkboot.initialize(
        "-flinkboot-configurations", "classpath:job-test.yaml",
        "--dry-run",
        "-custom-param", "custom-value"
    );

    MyApplicationConfig config = boot.configuration(MyApplicationConfig.class);

    assertAll(
        () -> assertNotNull(config),
        () -> assertTrue(boot.flag("dry-run")),
        () -> assertEquals("custom-value", boot.parameter("custom-param").orElseThrow())
    );
}

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3. Scheme prefixes

Each path passed to -flinkboot-configurations must specify a valid resource scheme:

Scheme prefix	Target location	Example
classpath:	Classpath resources (e.g. src/test/resources)	"classpath:job-test.yaml"
resource:	Alias for classpath resources	"resource:job-test.yaml"
file:	Absolute or relative file system paths	"file:/tmp/test-config.yaml"

Omitting the prefix will throw an UnrecognizedResourceException.