<!--
title: Optimize test case design
domain: app-frameworks
topic: Testing
language: Java
source: spring-projects/spring-boot
updated: 2025-06-26
url: https://awesomereviewers.com/reviewers/spring-boot-optimize-test-case-design/
-->

Write focused, efficient tests that validate core functionality without unnecessary complexity. Key principles:

1. Test one concept per case
2. Use appropriate test scope (unit vs integration)
3. Leverage modern testing tools

Instead of exhaustive parameterized tests:

```java
@ParameterizedTest
@ValueSource(ints = { -1, 0, 100 })
void testValues(int value) {
    // Testing simple pass-through logic
}
```

Prefer focused single test:

```java
@Test
void testValue() {
    // Test with representative value
}
```

For JSON validation, use specialized assertions:

```java
// Instead of string contains checks:
assertThat(entity.getBody()).contains("\"name\":\"test\"");

// Use structured assertions:
JsonContent body = new JsonContent(entity.getBody());
assertThat(body).extractingPath("name").isEqualTo("test");
```

When testing output, prefer CapturedOutput over complex mocks:

```java
@Test
void testOutput(CapturedOutput output) {
    // Trigger output
    assertThat(output).contains("expected message");
}
```

Reserve integration tests for validating system interactions that cannot be effectively tested at the unit level.