Random Params Resolver

A JUnit 5 extension that automatically generates random test data for your test method parameters. Stop writing boilerplate test fixtures — just annotate your parameters with @Randomize and focus on what matters.

Quick Start

@ExtendWith(RandomParametersExtension.class)
class MyTest {
  @Test
  void test_with_random_data(@Randomize int value, @Randomize String name) {
    // value and name are randomly generated each run
  }
}

Installation

Maven

<dependency>
  <groupId>io.github.lyang</groupId>
  <artifactId>random-params-resolver</artifactId>
  <version>VERSION</version>
  <scope>test</scope>
</dependency>

Gradle

testImplementation 'io.github.lyang:random-params-resolver:VERSION'

Supported Types

Type	Annotation Options	Default Range
int / Integer	intMin, intMax	[Integer.MIN_VALUE, Integer.MAX_VALUE)
long / Long	longMin, longMax	[Long.MIN_VALUE, Long.MAX_VALUE)
float / Float	floatMin, floatMax	[0, 1)
double / Double	doubleMin, doubleMax	[0, 1)
BigInteger	longMin, longMax	[Long.MIN_VALUE, Long.MAX_VALUE)
BigDecimal	doubleMin, doubleMax	[0, 1)
byte[]	length	5 bytes
String	length, unicodeBlocks	5 chars, BASIC_LATIN
RandomGenerator	seed	seeded from System.nanoTime()

Examples

Numeric Types

@ExtendWith(RandomParametersExtension.class)
class NumericTest {
  @Test
  void random_integers(@Randomize int a, @Randomize Integer b) {
    // each parameter gets a different random value
  }

  @Test
  void bounded_range(@Randomize(intMin = 1, intMax = 100) int value) {
    // value is in [1, 100)
  }

  @Test
  void floating_point(
      @Randomize(floatMin = 0.0f, floatMax = 1.0f) float ratio,
      @Randomize(doubleMin = -180.0, doubleMax = 180.0) double longitude) {
  }

  @Test
  void big_numbers(@Randomize BigInteger bigInt, @Randomize BigDecimal bigDec) {
  }
}

Strings and Byte Arrays

@ExtendWith(RandomParametersExtension.class)
class StringTest {
  @Test
  void random_string(@Randomize String value) {
    // 5 random BASIC_LATIN characters
  }

  @Test
  void custom_string(@Randomize(length = 20, unicodeBlocks = "EMOTICONS") String emojis) {
    // 20 random emoji characters
  }

  @Test
  void random_bytes(@Randomize(length = 16) byte[] token) {
    // 16 random bytes
  }
}

Reproducible Tests with Seeds

Every test run logs the seed used for each parameter:

INFO: Using seed 787681803879958 for MyTest#my_test#arg0

To reproduce a failure, pin the seed:

@Test
void reproduce_failure(@Randomize(seed = 787681803879958L) int value) {
  // always generates the same value
}

Direct Access to RandomGenerator

@Test
void custom_generation(@Randomize RandomGenerator random) {
  // use the generator directly for complex test data setup
  var ids = random.ints(10, 1, 1000).boxed().toList();
}

License

Apache-2.0