Datagen

Java library to generate random data (numbers, strings, dates) - to facilitate Randomized Testing. Randomization may be used to improve coverage, but it can also speed up the process of writing & running tests. Some use cases for randomization:

• Combinatorial Testing - helps reducing the number of test cases you need to write and run
• Fighting with Unique Constraints - do you have a test that registers users with unique username? And the next time you run the test it fails because such user already exists..
• "Wow, I didn't know about that" effect - sometimes randomization may discover tricky cases that you couldn't think of.
• Which one to pick? - often when choosing test data there is no clear winner of what value to pick. Randomization helps with that and ensures we're not prone to Pesticides Effect.

Example

import java.time.OffsetDateTime;

import static io.qala.datagen.RandomDate.beforeNow;
import static io.qala.datagen.RandomShortApi.*;

public class Dog {
    private String name;
    private OffsetDateTime timeOfBirth;
    private double weight;
    private double height;

    public static Dog random() {
        Dog dog = new Dog();
        dog.name = alphanumeric(1, 100);
        dog.timeOfBirth = nullOr(beforeNow().offsetDateTime());
        dog.weight = positiveDouble();
        dog.height = positiveInteger();
        return dog;
    }
}

JUnit5 Integration

@Alphanumeric(min = 2, max = 29, name = "middle value")
@Alphanumeric(length = 30, name = "max boundary")
@English(max=30)
void eachAnnotationInvokesTheTestOnceAndPassesParameters(String value, String name) {
    assertTrue(value.length() >= 1 && value.length() <= 31, "Failed case: " + name);
}

@RandomInt(min = 1, name = "greater than zero")
@RandomInt(max = -1, name = "less than zero")
void zeroInt_isNotPassed(int param, String name) {
    assertNotEquals(0, param, "Failed case: " + name);
}

Strings

import static io.qala.datagen.RandomValue.*;
import static io.qala.datagen.StringModifier.Impls.*;
import static io.qala.datagen.RandomShortApi.*;

Nulls & Blanks

Repeats

import static io.qala.datagen.RandomString.Type.*;
import static io.qala.datagen.RandomValue.*;
import static io.qala.datagen.Repeater.*;

repeat(length(4), NUMERIC).string("-").times(4)`

Result: "9338-8349-6940-7714"

Numbers

import static io.qala.datagen.RandomValue.*;
import static io.qala.datagen.RandomShortApi.*;

Collections/Arrays

import static io.qala.datagen.RandomElements.*;
import static io.qala.datagen.RandomShortApi.*;

Java Date

import static io.qala.datagen.RandomValue.*;

SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd");
between(f.parse("2015-01-01"), f.parse("2016-01-01")).date();

Result: 2015-11-30T08:33:20.349

Java8 DateTime

// Requires Java8 and qala-datagen-java8types dependency
import static io.qala.datagen.RandomDate.*;

Booleans

import static io.qala.datagen.RandomShortApi.*;

Functions (for Java8 lambdas)

import static io.qala.datagen.RandomShortApi.*;
Person person = new Person();

callOneOf(() -> person.firstName = english(5),
          () -> person.lastName = english(5));

Result: Person[null, "PDGRq"]

callNoneOrMore(() -> person.firstName = english(5),
               () -> person.lastName = english(5));

Result: Person[null, null]

callOneOrMore(() -> person.firstName = english(5),
              () -> person.lastName = english(5));

Result: Person["LjxYh", "UXoBt"]

Other

• Maven Central coordinates
• Occasional updates are posted in Twitter
• Our blog

Special thanks

To keep the lib tiny and get rid of extra dependencies (there are no transitive dependencies) some of the code was borrowed from these libs: Commons Lang, Commons Math. Hail to open source!