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Keeping Spring Boot Test Configurations Simple and Maintainable

·2 mins
Java Spring-Boot Testing
Table of Contents

How to manage application.yml files in Spring Boot tests without duplication.

Spring Boot applications rely on an application.yml file to define configuration. Things get a little trickier when writing tests, since both src/main/resources and src/test/resources can contain configuration files. Understanding how Spring Boot handles them will help you avoid duplication and keep test configuration clean.

How Spring Boot Resolves application.yml #

When running the application normally, Spring Boot loads configuration from src/main/resources/application.yml.

When running tests, the classpath is a combination of main and test outputs, with test classes and resources placed ahead of main ones.

This means:

  • If you only have src/main/resources/application.yml, that file will be used during tests as well.
  • If you also define src/test/resources/application.yml, the test version will take precedence. The main version won’t be loaded at all unless you explicitly import it.

So the test application.yml does not “merge” with the main one, it shadows it.

Our Definition of A Clean Setup #

Our main goal is avoiding duplication. Without a deliberate setup, you often end up copying the entire application.yml into src/test/resources and maintaining two versions side by side. This makes configuration brittle and harder to manage.

A clean setup should:

  • Keep the main configuration as the single source of truth.
  • Allow test-specific overrides without repeating the full configuration.

A Clean Setup with Profiles and Imports #

To avoid duplicating configuration between test and main, you can make the test configuration explicitly import the main configuration and then layer test-specific overrides on top.

1. src/test/resources/application.yml

spring:
  profiles:
    active: test
  config:
    import: file:src/main/resources/application.yml

This setup:

  • Activates the test profile whenever tests run, so it will load application-test.yml files.
  • Reuses the main application.yml by importing it.

2. src/test/resources/application-test.yml

spring:
  datasource:
    url: jdbc:h2:mem:testdb
  jpa:
    hibernate:
      ddl-auto: create-drop

Here you define overrides that apply only when the test profile is active. Typical use cases include swapping out the database connection, adjusting logging levels, or changing service endpoints.

Why This Works Well #

  • Single source of truth: Your main application.yml stays the canonical configuration.
  • Minimal duplication: Test-specific overrides live in one dedicated file.
  • Profile isolation: Tests always run with the test profile, avoiding accidental reliance on production defaults.
  • Explicit precedence: By importing the main config, you make it clear that tests extend it rather than replace it.