Unit Test Config Properties

Unit Testing Configuration Properties and Profiles

Overview

This skill provides patterns for unit testing @ConfigurationProperties bindings, environment-specific configurations, and property validation using JUnit 5. Covers testing property name mapping, type conversions, validation constraints, nested structures, and profile-specific configurations without full Spring context startup.

Key validation checkpoints:

• Property prefix matches between @ConfigurationProperties and test properties
• Validation triggers on @Validated classes with invalid values
• Type conversions work for Duration, DataSize, collections, and maps

When to Use

• Testing @ConfigurationProperties property binding
• Testing property name mapping and type conversions
• Validating configuration with @NotBlank, @Min, @Max, @Email constraints
• Testing environment-specific configurations (dev, prod)
• Testing nested property structures and collections
• Verifying default values when properties are not specified
• Fast configuration tests without Spring context startup

Instructions

1. Set up test dependencies: Add spring-boot-starter-test and AssertJ dependencies 2. Use ApplicationContextRunner: Test property bindings without starting full Spring context 3. Define property prefixes: Ensure @ConfigurationProperties(prefix = "...") matches test property paths 4. Test all property paths: Verify each property including nested structures and collections 5. Test validation constraints: Use context.hasFailed() to verify @Validated properties reject invalid values 6. Test type conversions: Verify Duration (30s), DataSize (50MB), collections, and maps convert correctly 7. Test default values: Verify properties have correct defaults when not specified in test properties 8. Test profile-specific configs: Use @Profile with ApplicationContextRunner for environment-specific configurations 9. Test edge cases: Include empty strings, null values, and type mismatches

Troubleshooting flow:

• If properties don't bind → Check prefix matches (kebab-case to camelCase conversion)
• If validation doesn't trigger → Verify @Validated annotation is present
• If context fails to start → Check dependencies and @ConfigurationProperties class structure

Examples

Setup: Test Dependencies

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-configuration-processor</artifactId>
  <scope>provided</scope>
</dependency>
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-test</artifactId>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.assertj</groupId>
  <artifactId>assertj-core</artifactId>
  <scope>test</scope>
</dependency>

Basic Pattern: Property Binding

@ConfigurationProperties(prefix = "app.security")
@Data
public class SecurityProperties {
  private String jwtSecret;
  private long jwtExpirationMs;
  private int maxLoginAttempts;
  private boolean enableTwoFactor;
}

class SecurityPropertiesTest {

  @Test
  void shouldBindPropertiesFromEnvironment() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.security.jwtSecret=my-secret-key",
        "app.security.jwtExpirationMs=3600000",
        "app.security.maxLoginAttempts=5",
        "app.security.enableTwoFactor=true"
      )
      .withBean(SecurityProperties.class)
      .run(context -> {
        SecurityProperties props = context.getBean(SecurityProperties.class);
        assertThat(props.getJwtSecret()).isEqualTo("my-secret-key");
        assertThat(props.getJwtExpirationMs()).isEqualTo(3600000L);
        assertThat(props.getMaxLoginAttempts()).isEqualTo(5);
        assertThat(props.isEnableTwoFactor()).isTrue();
      });
  }

  @Test
  void shouldUseDefaultValuesWhenPropertiesNotProvided() {
    new ApplicationContextRunner()
      .withPropertyValues("app.security.jwtSecret=key")
      .withBean(SecurityProperties.class)
      .run(context -> {
        SecurityProperties props = context.getBean(SecurityProperties.class);
        assertThat(props.getJwtSecret()).isEqualTo("key");
        assertThat(props.getMaxLoginAttempts()).isZero();
      });
  }
}

Validation Testing

@ConfigurationProperties(prefix = "app.server")
@Data
@Validated
public class ServerProperties {
  @NotBlank
  private String host;

  @Min(1)
  @Max(65535)
  private int port = 8080;

  @Positive
  private int threadPoolSize;
}

class ConfigurationValidationTest {

  @Test
  void shouldFailValidationWhenHostIsBlank() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.server.host=",
        "app.server.port=8080",
        "app.server.threadPoolSize=10"
      )
      .withBean(ServerProperties.class)
      .run(context -> {
        assertThat(context).hasFailed()
          .getFailure()
          .hasMessageContaining("host");
      });
  }

  @Test
  void shouldPassValidationWithValidConfiguration() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.server.host=localhost",
        "app.server.port=8080",
        "app.server.threadPoolSize=10"
      )
      .withBean(ServerProperties.class)
      .run(context -> {
        assertThat(context).hasNotFailed();
        assertThat(context.getBean(ServerProperties.class).getHost()).isEqualTo("localhost");
      });
  }
}

Type Conversion Testing

@ConfigurationProperties(prefix = "app.features")
@Data
public class FeatureProperties {
  private Duration cacheExpiry = Duration.ofMinutes(10);
  private DataSize maxUploadSize = DataSize.ofMegabytes(100);
  private List<String> enabledFeatures;
  private Map<String, String> featureFlags;
}

class TypeConversionTest {

  @Test
  void shouldConvertDurationFromString() {
    new ApplicationContextRunner()
      .withPropertyValues("app.features.cacheExpiry=30s")
      .withBean(FeatureProperties.class)
      .run(context -> {
        assertThat(context.getBean(FeatureProperties.class).getCacheExpiry())
          .isEqualTo(Duration.ofSeconds(30));
      });
  }

  @Test
  void shouldConvertCommaDelimitedList() {
    new ApplicationContextRunner()
      .withPropertyValues("app.features.enabledFeatures=feature1,feature2")
      .withBean(FeatureProperties.class)
      .run(context -> {
        assertThat(context.getBean(FeatureProperties.class).getEnabledFeatures())
          .containsExactly("feature1", "feature2");
      });
  }
}

For nested properties, profile-specific configurations, collection binding, and advanced validation patterns, see references/advanced-examples.md.

Best Practices

• Test all property bindings including nested structures and collections
• Test validation constraints for all @NotBlank, @Min, @Max, @Email, @Positive annotations
• Test both default and custom values to verify fallback behavior
• Use ApplicationContextRunner for fast context-free testing
• Test profile-specific configurations separately with @Profile
• Verify type conversions for Duration, DataSize, collections, and maps
• Test edge cases: empty strings, null values, type mismatches, out-of-range values

Constraints and Warnings

• Kebab-case to camelCase: Property app.my-property maps to myProperty in Java
• Loose binding: Spring Boot uses loose binding by default; use strict binding if needed
• `@Validated` required: Add @Validated annotation to enable constraint validation
• `@ConstructorBinding`: All parameters must be bindable when using constructor binding
• List indexing: Use [0], [1] notation; ensure sequential indexing for lists
• Duration format: Accepts ISO-8601 (PT30S) or simple syntax (30s, 1m, 2h)
• Context isolation: Each ApplicationContextRunner creates a new context with no shared state
• Profile activation: Use spring.profiles.active=profileName in withPropertyValues() for profile tests

Troubleshooting

Advanced ConfigurationProperties Testing Examples

Nested Configuration Properties

Complex Property Structure

@ConfigurationProperties(prefix = "app.database")
@Data
public class DatabaseProperties {
  private String url;
  private String username;
  private Pool pool = new Pool();
  private List<Replica> replicas = new ArrayList<>();

  @Data
  public static class Pool {
    private int maxSize = 10;
    private int minIdle = 5;
    private long connectionTimeout = 30000;
  }

  @Data
  public static class Replica {
    private String name;
    private String url;
    private int priority;
  }
}

class NestedPropertiesTest {

  @Test
  void shouldBindNestedProperties() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.database.url=jdbc:mysql://localhost/db",
        "app.database.username=admin",
        "app.database.pool.maxSize=20",
        "app.database.pool.minIdle=10",
        "app.database.pool.connectionTimeout=60000"
      )
      .withBean(DatabaseProperties.class)
      .run(context -> {
        DatabaseProperties props = context.getBean(DatabaseProperties.class);
        assertThat(props.getUrl()).isEqualTo("jdbc:mysql://localhost/db");
        assertThat(props.getPool().getMaxSize()).isEqualTo(20);
        assertThat(props.getPool().getConnectionTimeout()).isEqualTo(60000L);
      });
  }

  @Test
  void shouldBindListOfReplicas() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.database.replicas[0].name=replica-1",
        "app.database.replicas[0].url=jdbc:mysql://replica1/db",
        "app.database.replicas[0].priority=1",
        "app.database.replicas[1].name=replica-2",
        "app.database.replicas[1].url=jdbc:mysql://replica2/db",
        "app.database.replicas[1].priority=2"
      )
      .withBean(DatabaseProperties.class)
      .run(context -> {
        DatabaseProperties props = context.getBean(DatabaseProperties.class);
        assertThat(props.getReplicas()).hasSize(2);
        assertThat(props.getReplicas().get(0).getName()).isEqualTo("replica-1");
        assertThat(props.getReplicas().get(1).getPriority()).isEqualTo(2);
      });
  }
}

Profile-Specific Configurations

Environment-Specific Properties

@Configuration
@Profile("prod")
class ProductionConfiguration {
  @Bean
  public SecurityProperties securityProperties() {
    SecurityProperties props = new SecurityProperties();
    props.setEnableTwoFactor(true);
    props.setMaxLoginAttempts(3);
    return props;
  }
}

@Configuration
@Profile("dev")
class DevelopmentConfiguration {
  @Bean
  public SecurityProperties securityProperties() {
    SecurityProperties props = new SecurityProperties();
    props.setEnableTwoFactor(false);
    props.setMaxLoginAttempts(999);
    return props;
  }
}

class ProfileBasedConfigurationTest {

  @Test
  void shouldLoadProductionConfiguration() {
    new ApplicationContextRunner()
      .withPropertyValues("spring.profiles.active=prod")
      .withUserConfiguration(ProductionConfiguration.class)
      .run(context -> {
        SecurityProperties props = context.getBean(SecurityProperties.class);
        assertThat(props.isEnableTwoFactor()).isTrue();
        assertThat(props.getMaxLoginAttempts()).isEqualTo(3);
      });
  }

  @Test
  void shouldLoadDevelopmentConfiguration() {
    new ApplicationContextRunner()
      .withPropertyValues("spring.profiles.active=dev")
      .withUserConfiguration(DevelopmentConfiguration.class)
      .run(context -> {
        SecurityProperties props = context.getBean(SecurityProperties.class);
        assertThat(props.isEnableTwoFactor()).isFalse();
        assertThat(props.getMaxLoginAttempts()).isEqualTo(999);
      });
  }
}

Map-Based Properties

@ConfigurationProperties(prefix = "app.feature-flags")
@Data
public class FeatureFlagProperties {
  private Map<String, Boolean> flags = new HashMap<>();
  private Map<String, FeatureConfig> features = new HashMap<>();

  @Data
  public static class FeatureConfig {
    private boolean enabled;
    private String description;
    private List<String> allowedUsers;
  }
}

class MapPropertiesTest {

  @Test
  void shouldBindSimpleBooleanMap() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.feature-flags.flags.dark-mode=true",
        "app.feature-flags.flags.beta-features=false"
      )
      .withBean(FeatureFlagProperties.class)
      .run(context -> {
        FeatureFlagProperties props = context.getBean(FeatureFlagProperties.class);
        assertThat(props.getFlags()).containsEntry("dark-mode", true);
        assertThat(props.getFlags()).containsEntry("beta-features", false);
      });
  }

  @Test
  void shouldBindNestedMapStructures() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.feature-flags.features.payment.enabled=true",
        "app.feature-flags.features.payment.description=Payment module",
        "app.feature-flags.features.payment.allowedUsers[0]=admin",
        "app.feature-flags.features.payment.allowedUsers[1]=finance"
      )
      .withBean(FeatureFlagProperties.class)
      .run(context -> {
        FeatureFlagProperties props = context.getBean(FeatureFlagProperties.class);
        FeatureFlagProperties.FeatureConfig payment = props.getFeatures().get("payment");
        assertThat(payment.isEnabled()).isTrue();
        assertThat(payment.getDescription()).isEqualTo("Payment module");
        assertThat(payment.getAllowedUsers()).containsExactly("admin", "finance");
      });
  }
}

Default Values Testing

@ConfigurationProperties(prefix = "app.cache")
@Data
public class CacheProperties {
  private long ttlSeconds = 300;
  private int maxSize = 1000;
  private boolean enabled = true;
  private String cacheType = "IN_MEMORY";
}

class DefaultValuesTest {

  @Test
  void shouldUseDefaultValuesWhenNotSpecified() {
    new ApplicationContextRunner()
      .withBean(CacheProperties.class)
      .run(context -> {
        CacheProperties props = context.getBean(CacheProperties.class);
        assertThat(props.getTtlSeconds()).isEqualTo(300L);
        assertThat(props.getMaxSize()).isEqualTo(1000);
        assertThat(props.isEnabled()).isTrue();
        assertThat(props.getCacheType()).isEqualTo("IN_MEMORY");
      });
  }

  @Test
  void shouldOverrideDefaultValuesWithProvidedProperties() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.cache.ttlSeconds=600",
        "app.cache.cacheType=REDIS"
      )
      .withBean(CacheProperties.class)
      .run(context -> {
        CacheProperties props = context.getBean(CacheProperties.class);
        assertThat(props.getTtlSeconds()).isEqualTo(600L);
        assertThat(props.getCacheType()).isEqualTo("REDIS");
        assertThat(props.getMaxSize()).isEqualTo(1000); // Default unchanged
      });
  }
}

DataSize and Duration Advanced Patterns

@ConfigurationProperties(prefix = "app.upload")
@Data
public class UploadProperties {
  private DataSize maxFileSize = DataSize.ofMegabytes(10);
  private DataSize maxTotalSize = DataSize.ofGigabytes(1);
  private Duration timeout = Duration.ofSeconds(30);
  private List<DataSize> allowedExtensions;
}

class DataSizeDurationTest {

  @Test
  void shouldConvertVariousDurationFormats() {
    new ApplicationContextRunner()
      .withPropertyValues(
        "app.upload.timeout=2h30m",
        "app.upload.maxFileSize=25MB",
        "app.upload.maxTotalSize=5GB"
      )
      .withBean(UploadProperties.class)
      .run(context -> {
        UploadProperties props = context.getBean(UploadProperties.class);
        assertThat(props.getTimeout()).isEqualTo(Duration.ofHours(2).plusMinutes(30));
        assertThat(props.getMaxFileSize()).isEqualTo(DataSize.ofMegabytes(25));
        assertThat(props.getMaxTotalSize()).isEqualTo(DataSize.ofGigabytes(5));
      });
  }

  @Test
  void shouldHandleIsoDurationFormat() {
    new ApplicationContextRunner()
      .withPropertyValues("app.upload.timeout=PT1H30M")
      .withBean(UploadProperties.class)
      .run(context -> {
        assertThat(context.getBean(UploadProperties.class).getTimeout())
          .isEqualTo(Duration.ofHours(1).plusMinutes(30));
      });
  }
}

References

• Spring Boot ConfigurationProperties
• ApplicationContextRunner Testing
• Spring Boot Validation
• Relaxed Binding