Unit Test Config Properties

What it does

When your agent uses it

• Testing application configuration binding
• Validating YAML
• Application.properties files
• Verifying environment-specific settings

Example prompts

• “Use the unit-test-config-properties skill to provide patterns for unit testing @ConfigurationProperties classes with @ConfigurationPropertiesTest”
• “/unit-test-config-properties”

Requirements

• Pre-approved tools (allowed-tools): Read, Write, Bash, Glob, Grep

Workflow steps

9 steps, taken from the first numbered list in SKILL.md.

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

What it can do on your machine

Read from SKILL.md and the folder at commit fe73fb3. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Read
  • Write
  • Bash
  • Glob
  • Grep

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are java and xml).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Unit Test Config Properties loads about 2.3k tokens when it runs, and up to ~4.5k if it reads all its reference files. Until then it costs about 123 tokens; SKILL.md has 504 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~123

When it runs · the whole SKILL.md, loaded when a task matches

~2.3k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~4.5k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

• NotePre-approves every shell command (allowed-tools: Bash)SKILL.md

  allowed-tools: Read, Write, Bash, Glob, Grep

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from giuseppe-trisciuoglio/developer-kit at commit fe73fb3, republished under its MIT licence (© giuseppe-trisciuoglio). 504 words, ~2,303 tokens.

name

unit-test-config-properties

description

Provides patterns for unit testing `@ConfigurationProperties` classes with `@ConfigurationPropertiesTest`. Validates property binding, tests validation constraints, verifies default values, checks type conversions, and mocks property sources for Spring Boot configuration properties. Use when testing application configuration binding, validating YAML or application.properties files, verifying environment-specific settings, or testing nested property structures.

allowed-tools

Read, Write, Bash, Glob, Grep

<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>

@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();
      });
  }
}

@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");
      });
  }
}

@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");
      });
  }
}

© giuseppe-trisciuoglio, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file (references) in plugins/developer-kit-java/skills/unit-test-config-properties of giuseppe-trisciuoglio/developer-kit.

• SKILL.md
• references/advanced-examples.md

Open the folder on GitHubat commit fe73fb3