DataGen: A Java repository from edwardchen40

Datagen

Java library to generate random data (numbers, strings, dates) - to facilitate Randomized Testing. Randomization helps writing and running tests quicker as well improving the coverage. Just some use cases for randomization:

Combinatorial Testing - helps reducing the number of test cases you need to write and run
Fighting with Unique Constraints - a test registered a user with unique username? 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.

Strings

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

length(10).english() or english(10)
> "DcRZUNPrED"

upTo(10).alphanumeric() or alphanumeric(0, 10)
> "zG9G"

between(1, 10).numeric() or numeric(1, 10)
> "7167162"

length(5).unicode() or 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"

upTo(10).alphanumerics(5)
> ["cvA", "mTMDj0", "N", "", "iPOlGF9DsB"]

length(6).with(prefix("blah"), spaceRight()).numerics(3)
> ["blah8 ", "blah9 ", "blah2 "]

nullOrEmpty()
> ""

nullOrBlank()
> "    "

blankOr("string")
> null

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)
> "9338-8349-6940-7714"

Numbers

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

upTo(100).integer() or integer(100)
> 89

between(-100, 100).integer() or 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.*;

from("A", "B", "C", "D").sample() or sample("A", "B", "C", "D")
> "C"

from("A", "B", "C", "D").sample(2) or sampleMultiple(2, "A", "B", "C", "D")
> ["B", "D"]

from("A", "B").sampleWithReplacement(3)
> ["A", "A", "B"]

nullOr("string")
> "string"

Dates

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();
> "2015-11-30T08:33:20.349"

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

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.*;

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));
> Person[null, "PDGRq"]
      
callNoneOrMore(() -> person.firstName = english(5),
               () -> person.lastName = english(5));
> Person[null, null]      

callOneOrMore(() -> person.firstName = english(5),
              () -> person.lastName = english(5));
> Person["LjxYh", "UXoBt"]

Other

For convenience the repo is available both at BitBucket and at GitHub
Maven Central coordinates

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!

edwardchen40/DataGen