zio-test
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zio-test/zio.test/zio.test.laws

zio.test.laws

package zio.test.laws

The laws package provides functionality for describing laws as values. The fundamental abstraction is a set of ZLaws[Caps, R]. These laws model the laws that instances having a capability of type Caps are expected to satisfy. A capability Caps[_] is an abstraction describing some functionality that is common across different data types and obeys certain laws. For example, we can model the capability of two values of a type being compared for equality as follows:

trait Equal[-A] {
 def equal(a1: A, a2: A): Boolean
}

Definitions of equality are expected to obey certain laws:

  1. Reflexivity - a1 === a1
  2. Symmetry - a1 === a2 ==> a2 === a1
  3. Transitivity - (a1 === a2) && (a2 === a3) ==> (a1 === a3)

These laws define what the capabilities mean and ensure that it is safe to abstract across different instances with the same capability.

Using ZIO Test, we can represent these laws as values. To do so, we define each law using one of the ZLaws constructors. For example:

val transitivityLaw = ZLaws.Laws3[Equal]("transitivityLaw") {
 def apply[A: Equal](a1: A, a2: A, a3: A): TestResult =
   ???
}

We can then combine laws using the + operator:

val reflexivityLaw: = ???
val symmetryLaw:    = ???

val equalLaws = reflexivityLaw + symmetryLaw + transitivityLaw

Laws have a run method that takes a generator of values of type A and checks that those values satisfy the laws. In addition, objects can extend ZLawful to provide an even more convenient syntax for users to check that instances satisfy certain laws.

object Equal extends Lawful[Equal]

object Hash extends Lawful[Hash]

object Ord extends Lawful[Ord]

checkAllLaws(Equal + Hash + Ord)(Gen.int)

Note that capabilities compose seamlessly because of contravariance. We can combine laws describing different capabilities to construct a set of laws requiring that instances having all of the capabilities satisfy each of the laws.

Attributes

Members list

Type members

Classlikes

trait GenF[-R, F[_]]

A GenF knows how to construct a generator of F[A] values given a generator of A values for any A. For example, a GenF of List values knows how to generate lists with elements given a generator of elements of that type. You can think of GenF as a "recipe" for building generators for parameterized types.

A GenF knows how to construct a generator of F[A] values given a generator of A values for any A. For example, a GenF of List values knows how to generate lists with elements given a generator of elements of that type. You can think of GenF as a "recipe" for building generators for parameterized types.

Attributes

Companion
object
Supertypes
class Object
trait Matchable
class Any
object GenF

Attributes

Companion
trait
Supertypes
class Object
trait Matchable
class Any
Self type
GenF.type
trait GenF2[-R, F[_, _]]

A GenF knows how to construct a generator of F[A,B] values given a generator of A and generator of B values. For example, a GenF2 of Function1 values knows how to generate functions A => B with elements given a generator of elements of that type B.

A GenF knows how to construct a generator of F[A,B] values given a generator of A and generator of B values. For example, a GenF2 of Function1 values knows how to generate functions A => B with elements given a generator of elements of that type B.

Attributes

Companion
object
Supertypes
class Object
trait Matchable
class Any
object GenF2 extends FunctionVariants

Attributes

Companion
trait
Supertypes
class Object
trait Matchable
class Any
Self type
GenF2.type
object LawfulF

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
LawfulF.type
object LawfulF2

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
LawfulF2.type
object Laws

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
Laws.type
object Laws2

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
Laws2.type
object LawsF

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
LawsF.type
object LawsF2

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
LawsF2.type
trait ZLawful[-Caps[_], -R]

ZLawful[Caps, R] describes a capability that is expected to satisfy a set of laws. Lawful instances can be combined using + to describe a set of capabilities and all of the laws that those capabilities are expected to satisfy.

ZLawful[Caps, R] describes a capability that is expected to satisfy a set of laws. Lawful instances can be combined using + to describe a set of capabilities and all of the laws that those capabilities are expected to satisfy.

trait Equal[-A] {
 def equal(a1: A, a2: A): Boolean
}

object Equal extends Lawful[Equal] {
 val laws = ???
}

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
ZLawful[Caps, R]
trait ZLawful2[-CapsBoth[_, _], -CapsLeft[_], -CapsRight[_], -R]

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
ZLawful2[CapsBoth, CapsLeft, CapsRight, R]
object ZLawfulF

ZLawfulF[CapsF, Caps, R] describes a set of laws that a parameterized type F[A] with capabilities CapsF is expected to satisfy with respect to all types A that have capabilities Caps. Lawful instances can be combined using + to describe a set of capabilities and all of the laws that those capabilities are expected to satisfy.

ZLawfulF[CapsF, Caps, R] describes a set of laws that a parameterized type F[A] with capabilities CapsF is expected to satisfy with respect to all types A that have capabilities Caps. Lawful instances can be combined using + to describe a set of capabilities and all of the laws that those capabilities are expected to satisfy.

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
ZLawfulF.type
object ZLawfulF2

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
ZLawfulF2.type
abstract class ZLaws[-Caps[_], -R]

ZLaws[Caps, R] represents a set of laws that values with capabilities Caps are expected to satisfy. Laws can be run by providing a generator of values of a type A with the required capabilities to return a test result. Laws can be combined using + to produce a set of laws that require both sets of laws to be satisfied.

ZLaws[Caps, R] represents a set of laws that values with capabilities Caps are expected to satisfy. Laws can be run by providing a generator of values of a type A with the required capabilities to return a test result. Laws can be combined using + to produce a set of laws that require both sets of laws to be satisfied.

Attributes

Companion
object
Supertypes
class Object
trait Matchable
class Any
Known subtypes
class Law1[Caps]
class Law1ZIO[Caps, R]
class Law2[Caps]
class Law2ZIO[Caps, R]
class Law3[Caps]
class Law3ZIO[Caps, R]
Show all
Self type
ZLaws[Caps, R]
object ZLaws

Attributes

Companion
class
Supertypes
class Object
trait Matchable
class Any
Self type
ZLaws.type
abstract class ZLaws2[-CapsBoth[_, _], -CapsLeft[_], -CapsRight[_], -R]

Attributes

Companion
object
Supertypes
class Object
trait Matchable
class Any
Known subtypes
class Law1Left[CapsBoth, CapsLeft, CapsRight]
class Law1Right[CapsBoth, CapsLeft, CapsRight]
Self type
ZLaws2[CapsBoth, CapsLeft, CapsRight, R]
object ZLaws2

Attributes

Companion
class
Supertypes
class Object
trait Matchable
class Any
Self type
ZLaws2.type
object ZLawsF

ZLaws[CapsF, Caps, R] describes a set of laws that a parameterized type F[A] with capabilities CapsF is expected to satisfy with respect to all types A that have capabilities Caps. Laws can be run by providing a GenF that is capable of generating F[A] values given a generator of A values and a generator of values of some type A. Laws can be combined using + to produce a set of laws that require both sets of laws to be satisfied.

ZLaws[CapsF, Caps, R] describes a set of laws that a parameterized type F[A] with capabilities CapsF is expected to satisfy with respect to all types A that have capabilities Caps. Laws can be run by providing a GenF that is capable of generating F[A] values given a generator of A values and a generator of values of some type A. Laws can be combined using + to produce a set of laws that require both sets of laws to be satisfied.

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
ZLawsF.type
object ZLawsF2

Attributes

Supertypes
class Object
trait Matchable
class Any
Self type
ZLawsF2.type

Types

type Lawful[-Caps[_]] = ZLawful[Caps, Any]
type Lawful2[-CapsBoth[_, _], -CapsLeft[_], -CapsRight[_]] = ZLawful2[CapsBoth, CapsLeft, CapsRight, Any]
type Laws[-Caps[_]] = ZLaws[Caps, Any]
type Laws2[-CapsBoth[_, _], -CapsLeft[_], -CapsRight[_]] = ZLaws2[CapsBoth, CapsLeft, CapsRight, Any]

Value members

Concrete methods

def checkAllLaws[Caps[_], R, R1 <: R, A : Caps](lawful: ZLawful[Caps, R])(gen: Gen[R1, A])(implicit evidence$1: Caps[A], trace: Trace): ZIO[R1, Nothing, TestResult]

Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.

Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.

Attributes

def checkAllLaws[CapsBoth[_, _], CapsLeft[_], CapsRight[_], R, R1 <: R, A : CapsLeft, B : CapsRight](lawful: ZLawful2[CapsBoth, CapsLeft, CapsRight, R])(a: Gen[R1, A], b: Gen[R1, B])(implicit evidence$2: CapsLeft[A], evidence$3: CapsRight[B], CapsBoth: CapsBoth[A, B], trace: Trace): ZIO[R1, Nothing, TestResult]

Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.

Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.

Attributes

def checkAllLaws[CapsF[_[_]], Caps[_], R, R1 <: R, F[_] : CapsF, A : Caps](lawful: Covariant[CapsF, Caps, R])(genF: GenF[R1, F], gen: Gen[R1, A])(implicit evidence$4: CapsF[F], evidence$5: Caps[A], trace: Trace): ZIO[R1, Nothing, TestResult]
def checkAllLaws[CapsF[_[_]], Caps[_], R, R1 <: R, F[_] : CapsF, A : Caps](lawful: Contravariant[CapsF, Caps, R])(genF: GenF[R1, F], gen: Gen[R1, A])(implicit evidence$6: CapsF[F], evidence$7: Caps[A], trace: Trace): ZIO[R1, Nothing, TestResult]

Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.

Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.

Attributes

def checkAllLaws[CapsF[_[_]], Caps[_], R, R1 <: R, F[_] : CapsF, A : Caps](lawful: Invariant[CapsF, Caps, R])(genF: GenF[R1, F], gen: Gen[R1, A])(implicit evidence$8: CapsF[F], evidence$9: Caps[A], trace: Trace): ZIO[R1, Nothing, TestResult]

Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.

Checks that all values generated by a the specified generator satisfy the expected behavior of the lawful instance.

Attributes

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