
Java Testing Advanced
- 297 installs
- 40 repo stars
- Updated January 5, 2026
- pluginagentmarketplace/custom-plugin-java
java-testing-advanced is a Claude Code skill that helps developers ship resilient Java codebases using JUnit, Mockito, Testcontainers, contract tests, and flake controls before production releases.
About
java-testing-advanced is a Java-focused testing skill from pluginagentmarketplace/custom-plugin-java for backend developers preparing production releases. The skill covers advanced JUnit patterns, Mockito mocking strategies, Testcontainers integration tests, contract testing, and flake controls to reduce intermittent failures in CI. Developers reach for java-testing-advanced when a Java service needs stronger test coverage, realistic integration environments, or contract verification before deployment. Output includes test architecture guidance, example patterns, and release-ready testing practices across unit, integration, and contract layers.
- Testcontainers for real dependency coverage
- Mockito and stubbing strategy patterns
- Parameterized and property-based test design
- Contract and slice test architecture
- CI flake detection and isolation fixes
Java Testing Advanced by the numbers
- 297 all-time installs (skills.sh)
- +8 installs in the week ending Aug 4, 2026 (Skillselion tracking)
- Ranked #707 of 2,153 Testing & QA skills by installs in the Skillselion catalog
- Data as of Aug 4, 2026 (Skillselion catalog sync)
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| Installs | 297 |
|---|---|
| repo stars | ★ 40 |
| Last updated | January 5, 2026 |
| Repository | pluginagentmarketplace/custom-plugin-java ↗ |
How do you write advanced Java tests with Testcontainers?
Ship resilient Java codebases using advanced JUnit, Mockito, Testcontainers, contract tests, and flake controls before production releases.
Who is it for?
Java backend developers hardening services with integration, contract, and anti-flake testing before a production release.
Skip if: Beginner Java tutorials or teams not using JUnit, Mockito, or containerized integration tests.
When should I use this skill?
A developer asks for advanced Java testing with JUnit, Mockito, Testcontainers, contract tests, or CI flake controls.
What you get
JUnit test suites, Mockito mocks, Testcontainers integration tests, contract test specs, and flake-control patterns for Java CI.
- integration test suite
- contract test specification
- flake-control test patterns
By the numbers
- Covers JUnit, Mockito, Testcontainers, contract tests, and flake controls as five advanced Java testing approaches
Files
Java Testing Advanced Skill
Advanced testing techniques for comprehensive test coverage.
Overview
This skill covers advanced testing patterns including Testcontainers for integration testing, contract testing with Pact, mutation testing with PIT, and property-based testing.
When to Use This Skill
Use when you need to:
- Test with real databases (Testcontainers)
- Verify API contracts
- Find gaps with mutation testing
- Generate test cases automatically
Quick Reference
Testcontainers
@Testcontainers
@SpringBootTest
class OrderRepositoryIT {
@Container
static PostgreSQLContainer<?> postgres =
new PostgreSQLContainer<>("postgres:15")
.withDatabaseName("test")
.withUsername("test")
.withPassword("test");
@Container
static KafkaContainer kafka =
new KafkaContainer(DockerImageName.parse("confluentinc/cp-kafka:7.4.0"));
@DynamicPropertySource
static void configure(DynamicPropertyRegistry registry) {
registry.add("spring.datasource.url", postgres::getJdbcUrl);
registry.add("spring.kafka.bootstrap-servers", kafka::getBootstrapServers);
}
@Test
void shouldPersistOrder() {
Order saved = repository.save(new Order("item", 100.0));
assertThat(saved.getId()).isNotNull();
}
}Contract Testing (Pact)
@ExtendWith(PactConsumerTestExt.class)
class UserServiceContractTest {
@Pact(consumer = "order-service", provider = "user-service")
public RequestResponsePact createPact(PactDslWithProvider builder) {
return builder
.given("user exists")
.uponReceiving("get user request")
.path("/users/1")
.method("GET")
.willRespondWith()
.status(200)
.body(new PactDslJsonBody()
.integerType("id", 1)
.stringType("name", "John"))
.toPact();
}
@Test
@PactTestFor(pactMethod = "createPact")
void testGetUser(MockServer mockServer) {
User user = client.getUser(mockServer.getUrl(), 1L);
assertThat(user.getName()).isEqualTo("John");
}
}Mutation Testing (PIT)
<plugin>
<groupId>org.pitest</groupId>
<artifactId>pitest-maven</artifactId>
<version>1.15.0</version>
<configuration>
<targetClasses>
<param>com.example.service.*</param>
</targetClasses>
<mutationThreshold>80</mutationThreshold>
</configuration>
</plugin>Property-Based Testing
@Property
void shouldReverseListTwiceReturnsOriginal(@ForAll List<Integer> list) {
Collections.reverse(list);
Collections.reverse(list);
// Original order restored
}Testing Pyramid
/\ E2E Tests (few)
/ \ Contract Tests
/----\ Integration Tests
/------\ Unit Tests (many)Troubleshooting
| Problem | Solution |
|---|---|
| Container slow | Reuse containers |
| Port conflicts | Random ports |
| Flaky tests | Wait strategies |
Usage
Skill("java-testing-advanced")# java-testing-advanced Configuration
# Category: testing
# Generated: 2025-12-30
skill:
name: java-testing-advanced
version: "1.0.0"
category: testing
settings:
# Default settings for java-testing-advanced
enabled: true
log_level: info
# Category-specific defaults
validation:
strict_mode: false
auto_fix: false
output:
format: markdown
include_examples: true
# Environment-specific overrides
environments:
development:
log_level: debug
validation:
strict_mode: false
production:
log_level: warn
validation:
strict_mode: true
# Integration settings
integrations:
# Enable/disable integrations
git: true
linter: true
formatter: true
{
"$schema": "http://json-schema.org/draft-07/schema#",
"title": "java-testing-advanced Configuration Schema",
"type": "object",
"properties": {
"skill": {
"type": "object",
"properties": {
"name": {
"type": "string"
},
"version": {
"type": "string",
"pattern": "^\\d+\\.\\d+\\.\\d+$"
},
"category": {
"type": "string",
"enum": [
"api",
"testing",
"devops",
"security",
"database",
"frontend",
"algorithms",
"machine-learning",
"cloud",
"containers",
"general"
]
}
},
"required": [
"name",
"version"
]
},
"settings": {
"type": "object",
"properties": {
"enabled": {
"type": "boolean",
"default": true
},
"log_level": {
"type": "string",
"enum": [
"debug",
"info",
"warn",
"error"
]
}
}
}
},
"required": [
"skill"
]
}patterns:
unit_testing:
framework: JUnit 5
mocking: Mockito
assertions: AssertJ
integration:
framework: Spring Test
containers: Testcontainers
e2e:
framework: Selenium/Playwright
Java Testing Advanced Guide
Overview
This guide provides comprehensive documentation for the java-testing-advanced skill in the custom-plugin-java plugin.
Category: Testing
Quick Start
Prerequisites
- Familiarity with testing concepts
- Development environment set up
- Plugin installed and configured
Basic Usage
# Invoke the skill
claude "java-testing-advanced - [your task description]"
# Example
claude "java-testing-advanced - analyze the current implementation"Core Concepts
Key Principles
1. Consistency - Follow established patterns 2. Clarity - Write readable, maintainable code 3. Quality - Validate before deployment
Best Practices
- Always validate input data
- Handle edge cases explicitly
- Document your decisions
- Write tests for critical paths
Common Tasks
Task 1: Basic Implementation
# Example implementation pattern
def implement_java_testing_advanced(input_data):
"""
Implement java-testing-advanced functionality.
Args:
input_data: Input to process
Returns:
Processed result
"""
# Validate input
if not input_data:
raise ValueError("Input required")
# Process
result = process(input_data)
# Return
return resultTask 2: Advanced Usage
For advanced scenarios, consider:
- Configuration customization via
assets/config.yaml - Validation using
scripts/validate.py - Integration with other skills
Troubleshooting
Common Issues
| Issue | Cause | Solution |
|---|---|---|
| Skill not found | Not installed | Run plugin sync |
| Validation fails | Invalid config | Check config.yaml |
| Unexpected output | Missing context | Provide more details |
Related Resources
- SKILL.md - Skill specification
- config.yaml - Configuration options
- validate.py - Validation script
---
Last updated: 2025-12-30
Java Testing Advanced Patterns
Design Patterns
Pattern 1: Input Validation
Always validate input before processing:
def validate_input(data):
if data is None:
raise ValueError("Data cannot be None")
if not isinstance(data, dict):
raise TypeError("Data must be a dictionary")
return TruePattern 2: Error Handling
Use consistent error handling:
try:
result = risky_operation()
except SpecificError as e:
logger.error(f"Operation failed: {e}")
handle_error(e)
except Exception as e:
logger.exception("Unexpected error")
raisePattern 3: Configuration Loading
Load and validate configuration:
import yaml
def load_config(config_path):
with open(config_path) as f:
config = yaml.safe_load(f)
validate_config(config)
return configAnti-Patterns to Avoid
❌ Don't: Swallow Exceptions
# BAD
try:
do_something()
except:
pass✅ Do: Handle Explicitly
# GOOD
try:
do_something()
except SpecificError as e:
logger.warning(f"Expected error: {e}")
return default_valueCategory-Specific Patterns: Testing
Recommended Approach
1. Start with the simplest implementation 2. Add complexity only when needed 3. Test each addition 4. Document decisions
Common Integration Points
- Configuration:
assets/config.yaml - Validation:
scripts/validate.py - Documentation:
references/GUIDE.md
---
Pattern library for java-testing-advanced skill
#!/usr/bin/env python3
"""
Validation script for java-testing-advanced skill.
Category: testing
"""
import os
import sys
import yaml
import json
from pathlib import Path
def validate_config(config_path: str) -> dict:
"""
Validate skill configuration file.
Args:
config_path: Path to config.yaml
Returns:
dict: Validation result with 'valid' and 'errors' keys
"""
errors = []
if not os.path.exists(config_path):
return {"valid": False, "errors": ["Config file not found"]}
try:
with open(config_path, 'r') as f:
config = yaml.safe_load(f)
except yaml.YAMLError as e:
return {"valid": False, "errors": [f"YAML parse error: {e}"]}
# Validate required fields
if 'skill' not in config:
errors.append("Missing 'skill' section")
else:
if 'name' not in config['skill']:
errors.append("Missing skill.name")
if 'version' not in config['skill']:
errors.append("Missing skill.version")
# Validate settings
if 'settings' in config:
settings = config['settings']
if 'log_level' in settings:
valid_levels = ['debug', 'info', 'warn', 'error']
if settings['log_level'] not in valid_levels:
errors.append(f"Invalid log_level: {settings['log_level']}")
return {
"valid": len(errors) == 0,
"errors": errors,
"config": config if not errors else None
}
def validate_skill_structure(skill_path: str) -> dict:
"""
Validate skill directory structure.
Args:
skill_path: Path to skill directory
Returns:
dict: Structure validation result
"""
required_dirs = ['assets', 'scripts', 'references']
required_files = ['SKILL.md']
errors = []
# Check required files
for file in required_files:
if not os.path.exists(os.path.join(skill_path, file)):
errors.append(f"Missing required file: {file}")
# Check required directories
for dir in required_dirs:
dir_path = os.path.join(skill_path, dir)
if not os.path.isdir(dir_path):
errors.append(f"Missing required directory: {dir}/")
else:
# Check for real content (not just .gitkeep)
files = [f for f in os.listdir(dir_path) if f != '.gitkeep']
if not files:
errors.append(f"Directory {dir}/ has no real content")
return {
"valid": len(errors) == 0,
"errors": errors,
"skill_name": os.path.basename(skill_path)
}
def main():
"""Main validation entry point."""
skill_path = Path(__file__).parent.parent
print(f"Validating java-testing-advanced skill...")
print(f"Path: {skill_path}")
# Validate structure
structure_result = validate_skill_structure(str(skill_path))
print(f"\nStructure validation: {'PASS' if structure_result['valid'] else 'FAIL'}")
if structure_result['errors']:
for error in structure_result['errors']:
print(f" - {error}")
# Validate config
config_path = skill_path / 'assets' / 'config.yaml'
if config_path.exists():
config_result = validate_config(str(config_path))
print(f"\nConfig validation: {'PASS' if config_result['valid'] else 'FAIL'}")
if config_result['errors']:
for error in config_result['errors']:
print(f" - {error}")
else:
print("\nConfig validation: SKIPPED (no config.yaml)")
# Summary
all_valid = structure_result['valid']
print(f"\n==================================================")
print(f"Overall: {'VALID' if all_valid else 'INVALID'}")
return 0 if all_valid else 1
if __name__ == "__main__":
sys.exit(main())
Related skills
FAQ
What Java testing tools does java-testing-advanced cover?
java-testing-advanced covers JUnit, Mockito, Testcontainers, contract tests, and flake controls for Java codebases. The skill targets resilient test suites developers need before shipping production Java services.
When should developers use java-testing-advanced?
Developers should use java-testing-advanced before production releases when Java services need stronger integration, contract, and anti-flake coverage. The skill suits backend teams already using JUnit and Mockito who want Testcontainers-based realism.