Datagen

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.*;

| Flexible API | Short API | Result |----------------------------------------------------------|----------------------|-------- | length(10).english() |english(10) | "DcRZUNPrED" | between(1, 10).alphanumeric() |alphanumeric(0, 10) | "zG9G" | between(1, 10).numeric() |numeric(1, 10) | "7167162" | length(5).unicode() |unicode(5) | "䂞ꂣ뢧䯺婜" | length(5).string("A_ B") | | " _B B" | length(10).with(specialSymbol()).english() | | "hOzKEV#iWv" | length(10).with(oneOf("_,")).english() | | "dwei,cNTfW" | length(5).with(spaces()).numeric() | | "874 9 " | length(3).with(spaceLeft()).english() | | " mT" | length(4).with(spacesRight(2)).english() | | "hF " | length(10).with(prefix("BLAH")).numeric() | | "BLAH453677" | between(1, 10).alphanumerics(4) | | ["cvA", "mTMDj0", "N", ""] | | mixedCase("blah") | "bLaH"

Nulls & Blanks

| API | Result |----------------------|------------------------ | nullOrEmpty() | "", null | nullOrBlank() | "", " ", null | nullOr(10L) | null, 10L | nullOr("string") | null, "string" | blankOr("string") | "", " ", null, "string"

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.*;

|Flexible API | Short API | Result |---------------------------------------------------------|----------------------|-------- |between(0, 100).integer() | integer(100) | 89 |between(-100, 100).integer() | integer(-100, 100) | -19 | | positiveInteger() | 3432145 | | Long() | 7635811362052252913 | | negativeDouble() | -8.9946257128846746E18

Collections/Arrays

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

|Flexible API | Short API | Result |---------------------------------------------------------|----------------------------------------|-------- |from("A", "B", "C", "D").sample() | sample("A", "B", "C") | "C" |from("A", "B", "C", "D").sample(2) | sampleMultiple(2, "A", "B", "C") | ["B", "A"] |from("A", "B").sampleWithReplacement(3) | | ["A", "A", "B"] |from("A", "B", "C").shuffled() | shuffled("A", "B", "C") | ["C", "A", "B"]

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.*;

API | Result ---------------------------------------------------|-------- plusMinus100Years().zonedDateTime() | 1937-09-27T01:16:15.925440485+01:00[Europe/Belgrade] since(yearAgo()).instant() | 2015-11-30T08:39:28.397051483Z before(now()).instant() | -241279778-02-14T16:07:18.061693370Z between(yearsAgo(2), startOfMonth()).localDate() | 2014-09-30

Booleans

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

API | Result ---------------------------------------------------|-------- bool() or weighedTrue(0.5) | false bools(4) | [false, true, true, false] nullableBool() | Boolean.TRUE

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!