unit-test-parameterized

Unit Test Parameterized is a Java testing-guidance skill that provides patterns for writing data-driven unit tests with JUnit 5's parameterized testing support. It solves the problem of test duplication: instead of copying the same test method for each input, it shows how to run one test body across many inputs, which is ideal for boundary-value analysis and covering multiple scenarios from a single method.

The skill covers the full range of JUnit 5 argument sources — @ValueSource for simple primitives, strings, and enums; @CsvSource for tabular data; @MethodSource for complex objects and multi-argument cases; @EnumSource for enum values; and a custom @ArgumentsSource via an ArgumentsProvider implementation. It demonstrates readable custom display names using placeholders like {0}, error-condition testing with assertThatThrownBy, and integration with AssertJ assertions. It also documents best practices (descriptive display names, testing min/max/zero/edge cases, one focused assertion per parameter set) and constraints and warnings, such as matching parameter counts to the method signature, the primitives-only limitation of @ValueSource, CSV escaping rules for commas, and the requirement that @MethodSource factory methods be static.

It targets Java developers using JUnit 5 who want cleaner, more thorough tests. Use cases include validating input across many combinations (for example, email-validation truth tables), boundary analysis on numeric ranges, exercising all enum values, and asserting exceptions for invalid input. It is standard test-authoring guidance with no risky behavior.