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!